文章
Dummer. ゛☀
2017年09月17日
There are over 1200 known species of whiteflies, most of which feed on only one or a few species of plants each. Some are pests on valuable crops such as the sweet potato whitefly (Bemisia tabaci). Others, like the greenhouse whitefly (Trialeurodes vaporariorum), feed on a broad range of herbaceous plants both inside the greenhouse and outside in the garden. Some of the host plants that the greenhouse whitefly attacks are the tomato, fuchsia, lantana, and coleus.
The silverleaf whitefly (Bemisia argentifolii) has been found on as many as 500 hosts such as canna lilies, bearded iris, crepe myrtle, lantana, petunia, and rose.
Whiteflies are one of the most difficult insect pests to control. They are not true flies but are more closely related to aphids, mealybugs, and scale, which are also sap-sucking insects. In some parts of the country, some species of whitefly can transmit several plant viruses.
Symptoms and Diagnosis
Identification of the whitefly is easy as a white cloud of insects rise from foliage when disturbed. The adults are about 1/16 to 1/10 inch in length, wedgeshaped, and appear powdery. Infested leaves may show little if any symptoms or may be mottled and yellow. Leaves will also become coated with a sticky substance called honeydew, which is secreted by feeding whitefly nymphs and adults. A black, sooty mold may sometimes grow on the honeydew. Sooty mold does not damage the leaf. The feeding, however, removes nutrients from the plant, which results in stunting, poor growth, defoliation, reduced yields, and sometimes death. On certain plants the silverleaf whitefly causes specific damage symptoms such as silvering of leaves on squash, irregular ripening in tomato, whitestalk in broccoli and cauliflower, light root in carrots, and white stem in poinsettia.
Life Cycle
The whitefly spends its winters in weeds and ornamental plants, migrating to crops and gardens in spring and summer. Once temperatures warm up in the summer, populations can build rapidly with the highest populations probably occurring in late summer. They lay their tiny eggs on the undersides of leaves. Adult females usually lay between 200 to 400 eggs. Sometimes the eggs are deposited in a circular pattern (not true in all species) in groups of 30 to 40 as the female will often keep her mouth part in the plant to feed while moving in a circle to deposit eggs. Within about a week the eggs hatch into flattened nymphs, called crawlers that wander about the plant. Soon, they insert their mouth part and begin to feed. The first stage has legs and antennae, but these are lost after the first molt and the flattened, oval-shaped larvae stay fixed at one feeding site. The last part of the fourth instar is the pupa. Adults emerge from the pupa through a Tshaped slit and soon mate and reproduce. The adults live about one month. Within a population, all life stages are present and generations often overlap.
Integrated Pest Management Strategies
1. Inspection. Inspect all new plants planted in the garden for whiteflies. Inspect regularly and remove by hand older leaves that are heavily infested with whiteflies in a non-mobile nymphal stage.
2. Biological control. Whiteflies have many natural enemies in the garden setting including spiders, lady beetles, and lacewings. However, these predators are not effective if there is a frequent use of insecticides.
3. Mechanical control. The use of traps can be very helpful in controlling light infestations. Make yellow sticky traps about 12 x 6 inches and coat them with a sticky substance such as Tanglefoot, petroleum jelly, or heavy grade motor oil. Hang the traps vertically near the affected plants. The adults are attracted to yellow. Traps are also commercially available. Use one trap per plant.
4. Chemical control. Whiteflies have developed resistance to some chemicals. Because of this resistance, a certain product may work well in one area but not in another. Resistance may be delayed by alternating the types of chemicals used. In addition, the egg and non-feeding pupa stages are generally not as susceptible to insecticides as are the adults and nymphs. Consequently, eradication of a whitefly population usually requires four to five applications of a registered insecticide at five to seven day intervals. Be sure the applications are made to the lower leaf surface, and apply as soon as whiteflies are detected. Do not wait until populations become severe.
Before using any insecticide for whitefly control, make sure that the site and target plant are both listed on the label. Follow label directions carefully.
5. Chemicals. Some of the over-the-counter chemicals which could be used are malathion, imidacloprid, permethrin, or pyrethrins. Insecticidal soap, petroleum oil, and insect growth regulators can also be effective.
The silverleaf whitefly (Bemisia argentifolii) has been found on as many as 500 hosts such as canna lilies, bearded iris, crepe myrtle, lantana, petunia, and rose.
Whiteflies are one of the most difficult insect pests to control. They are not true flies but are more closely related to aphids, mealybugs, and scale, which are also sap-sucking insects. In some parts of the country, some species of whitefly can transmit several plant viruses.
Symptoms and Diagnosis
Identification of the whitefly is easy as a white cloud of insects rise from foliage when disturbed. The adults are about 1/16 to 1/10 inch in length, wedgeshaped, and appear powdery. Infested leaves may show little if any symptoms or may be mottled and yellow. Leaves will also become coated with a sticky substance called honeydew, which is secreted by feeding whitefly nymphs and adults. A black, sooty mold may sometimes grow on the honeydew. Sooty mold does not damage the leaf. The feeding, however, removes nutrients from the plant, which results in stunting, poor growth, defoliation, reduced yields, and sometimes death. On certain plants the silverleaf whitefly causes specific damage symptoms such as silvering of leaves on squash, irregular ripening in tomato, whitestalk in broccoli and cauliflower, light root in carrots, and white stem in poinsettia.
Life Cycle
The whitefly spends its winters in weeds and ornamental plants, migrating to crops and gardens in spring and summer. Once temperatures warm up in the summer, populations can build rapidly with the highest populations probably occurring in late summer. They lay their tiny eggs on the undersides of leaves. Adult females usually lay between 200 to 400 eggs. Sometimes the eggs are deposited in a circular pattern (not true in all species) in groups of 30 to 40 as the female will often keep her mouth part in the plant to feed while moving in a circle to deposit eggs. Within about a week the eggs hatch into flattened nymphs, called crawlers that wander about the plant. Soon, they insert their mouth part and begin to feed. The first stage has legs and antennae, but these are lost after the first molt and the flattened, oval-shaped larvae stay fixed at one feeding site. The last part of the fourth instar is the pupa. Adults emerge from the pupa through a Tshaped slit and soon mate and reproduce. The adults live about one month. Within a population, all life stages are present and generations often overlap.
Integrated Pest Management Strategies
1. Inspection. Inspect all new plants planted in the garden for whiteflies. Inspect regularly and remove by hand older leaves that are heavily infested with whiteflies in a non-mobile nymphal stage.
2. Biological control. Whiteflies have many natural enemies in the garden setting including spiders, lady beetles, and lacewings. However, these predators are not effective if there is a frequent use of insecticides.
3. Mechanical control. The use of traps can be very helpful in controlling light infestations. Make yellow sticky traps about 12 x 6 inches and coat them with a sticky substance such as Tanglefoot, petroleum jelly, or heavy grade motor oil. Hang the traps vertically near the affected plants. The adults are attracted to yellow. Traps are also commercially available. Use one trap per plant.
4. Chemical control. Whiteflies have developed resistance to some chemicals. Because of this resistance, a certain product may work well in one area but not in another. Resistance may be delayed by alternating the types of chemicals used. In addition, the egg and non-feeding pupa stages are generally not as susceptible to insecticides as are the adults and nymphs. Consequently, eradication of a whitefly population usually requires four to five applications of a registered insecticide at five to seven day intervals. Be sure the applications are made to the lower leaf surface, and apply as soon as whiteflies are detected. Do not wait until populations become severe.
Before using any insecticide for whitefly control, make sure that the site and target plant are both listed on the label. Follow label directions carefully.
5. Chemicals. Some of the over-the-counter chemicals which could be used are malathion, imidacloprid, permethrin, or pyrethrins. Insecticidal soap, petroleum oil, and insect growth regulators can also be effective.
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文章
Dummer. ゛☀
2017年09月17日
Two of the most damaging insects on perennial plants are the tarnished plant bug, Lygus lineolaris, and the four-lined plant bug, Poecilocapsus lineatus. These two plant bugs can cause serious problems because they have such a wide variety of host plants. The four-lined plant bug feeds on 250 plant species which are mostly herbaceous. The tarnished plant bug is a problem on a wide variety of ornamental flowers.
Symptoms and Diagnosis
Damage varies slightly from the two plant bugs. The four-lined plant bugs cause small (1/16 inch), discolored areas on leaves where they suck out cell juices. Injured areas will turn black or become translucent, and after several weeks, the dead tissue may drop out, leaving small holes. The adults feed on the upper surfaces of leaves and are voracious feeders. The topmost leaves will generally be the first to be injured.
Damage from the tarnished plant bug is in the form of distorted foliage or disbudded plants. This damage is caused by the overwintered adults which attack swollen and opening buds in the early spring. The disbudding will cause the plant to be short and bushy. If the attack takes place after shoot elongation begins, the tip will often turn black and die, or it will be so damaged that shoot stunting or distortion occurs. Stems frequently break at the injured area.
Life Cycle
The four-lined plant bug overwinters as eggs inserted into a slit near the top of tender shoots. Nymphs emerge from the eggs in May. Nymphal coloring varies from bright red to yellow. The species requires about 30 days to complete nymphal development. Forewings of adults are yellow, but may turn bright green. However, the four black stripes that give the insect its name remain distinct. This species normally has one generation a year.
Adults of the tarnished plant bug overwinter as adults in leaf litter. Beginning in the spring, they lay eggs mainly in the stems and flowers of herbaceous plants. After hatching, the young nymphs usually remain to feed on the same plant until they mature. The nymph is green or pale yellow and grows rapidly. Adults are capable flyers and readily move from place to place. There may be two to five generations per year. In midsummer, a life cycle may be completed in about 25 days. By late summer, populations can become very abundant.
Integrated Pest Management Strategies
1. Live with the damage. Since damage is often cosmetic, some damage can be tolerated. Often, natural predators will keep the insects under control.
2. Remove leaf litter. To limit problems in coming years, clean up leaf litter to avoid overwintering sites for tarnished plant bugs.
3. Prune out egg masses. Learn to identify the egg masses of four-lined plant bugs and prune them out in winter.
4. Use insecticidal soaps. If populations are high enough, spraying with an insecticidal soap may be necessary. Because the tarnished plant bug can go through many generations in a single year and cause great damage to a plant, it is best to initiate control when it first appears.
5. If necessary, use chemical insecticides. Plant bugs can be controlled with malathion, and carbaryl (Sevin).
Symptoms and Diagnosis
Damage varies slightly from the two plant bugs. The four-lined plant bugs cause small (1/16 inch), discolored areas on leaves where they suck out cell juices. Injured areas will turn black or become translucent, and after several weeks, the dead tissue may drop out, leaving small holes. The adults feed on the upper surfaces of leaves and are voracious feeders. The topmost leaves will generally be the first to be injured.
Damage from the tarnished plant bug is in the form of distorted foliage or disbudded plants. This damage is caused by the overwintered adults which attack swollen and opening buds in the early spring. The disbudding will cause the plant to be short and bushy. If the attack takes place after shoot elongation begins, the tip will often turn black and die, or it will be so damaged that shoot stunting or distortion occurs. Stems frequently break at the injured area.
Life Cycle
The four-lined plant bug overwinters as eggs inserted into a slit near the top of tender shoots. Nymphs emerge from the eggs in May. Nymphal coloring varies from bright red to yellow. The species requires about 30 days to complete nymphal development. Forewings of adults are yellow, but may turn bright green. However, the four black stripes that give the insect its name remain distinct. This species normally has one generation a year.
Adults of the tarnished plant bug overwinter as adults in leaf litter. Beginning in the spring, they lay eggs mainly in the stems and flowers of herbaceous plants. After hatching, the young nymphs usually remain to feed on the same plant until they mature. The nymph is green or pale yellow and grows rapidly. Adults are capable flyers and readily move from place to place. There may be two to five generations per year. In midsummer, a life cycle may be completed in about 25 days. By late summer, populations can become very abundant.
Integrated Pest Management Strategies
1. Live with the damage. Since damage is often cosmetic, some damage can be tolerated. Often, natural predators will keep the insects under control.
2. Remove leaf litter. To limit problems in coming years, clean up leaf litter to avoid overwintering sites for tarnished plant bugs.
3. Prune out egg masses. Learn to identify the egg masses of four-lined plant bugs and prune them out in winter.
4. Use insecticidal soaps. If populations are high enough, spraying with an insecticidal soap may be necessary. Because the tarnished plant bug can go through many generations in a single year and cause great damage to a plant, it is best to initiate control when it first appears.
5. If necessary, use chemical insecticides. Plant bugs can be controlled with malathion, and carbaryl (Sevin).
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文章
Dummer. ゛☀
2017年09月17日
Spider mites are very common pests of outdoor plants. The mites suck juices from the plants, causing the plants to look dull and unhealthy. Mites also cause plants to lose vigor so that they may be unable to overcome a severe infestation, resulting in the plant's death. In Missouri, the most common outdoor spider mite is the two-spotted spider mite. The spruce spider mite infects conifers such as spruce, juniper, and arborvitae. They are less than 1/60th inch in size and difficult to see without a magnifying lens. They are not insects but rather a member of the spider family in which all members have eight legs.
Symptoms and Diagnosis
Spider mites are among the most ubiquitous of pests, attacking a wide variety of field, garden, greenhouse, nursery, and ornamental plants, as well as several weed species. Infestations of two-spotted spider mites result in the bleaching and stippling of leaves. Severe infestations may cause entire leaves to become bronzed, curled, and completely enveloped in sheets of webbing. Damage to the foliage may result in leaf drop and reduction in the overall vitality of the plant. When a leaf or branch is tapped over a white sheet of paper, the mites appear as small specks that resemble dust or pepper and may be seen to move.
Life Cycle
Adult female spider mites overwinter under loose bark, in cracks in the soil, in leaf litter, and in other protected places. In the spring, adults emerge and begin laying eggs. Each female typically deposits 70 eggs and lives for only 30 days. Eggs hatch in 5–7 days. As many as 10 generations may occur each year. The young look similar to the adults, but newly hatched young have only six legs and do not possess the characteristic dark spots on the back. Reproduction of the two-spotted spider mite is favored by hot, dry conditions, so serious damage is likely to occur in mid-July to September. The spruce spider mite is most active durng cooler weather in Spring and Fall.
Integrated Pest Management Strategies
1. Knock mites off plants with water. Spraying with a strong stream of water (particularly the undersides of leaves) will provide some control. Spray plants frequently to control future buildups. For severe infestations, affected plants or plant parts can be removed and destroyed. There are several natural predators that feed on spider mites. The use of chemical insecticides to control other garden pests can result in the death of these beneficial insects and a subsequent increase in the population of spider mites.
2. Use insecticidal soap. Insecticidal soaps specially formulated to kill insects and not damage plants are effective if used frequently until the problem is under control.
3. Use superior horticultural oil sprays. Highly refined oils sold as superior or horticultural oils are also very effective in controlling spider mites. The oil suffocates the mites. Unlike dormant oils, these oils are highly refined and under proper conditions, can be applied to plant foliage without damage. Follow label directions to avoid damage to some plants that may be sensitive. Superior oils are considered nontoxic and are less likely to kill beneficial insects.
4. Use chemical insecticides or miticides. A very safe product made from the seeds of a tropical tree is called Neem. It is commercially available under the name Margosan-O. Other chemical controls include malathion, bifenthrin, cyfluthrin, and kelthane. Be sure to follow all label directions when using pesticides. Many pesticides are very harmful to bees and fish when used improperly.
Symptoms and Diagnosis
Spider mites are among the most ubiquitous of pests, attacking a wide variety of field, garden, greenhouse, nursery, and ornamental plants, as well as several weed species. Infestations of two-spotted spider mites result in the bleaching and stippling of leaves. Severe infestations may cause entire leaves to become bronzed, curled, and completely enveloped in sheets of webbing. Damage to the foliage may result in leaf drop and reduction in the overall vitality of the plant. When a leaf or branch is tapped over a white sheet of paper, the mites appear as small specks that resemble dust or pepper and may be seen to move.
Life Cycle
Adult female spider mites overwinter under loose bark, in cracks in the soil, in leaf litter, and in other protected places. In the spring, adults emerge and begin laying eggs. Each female typically deposits 70 eggs and lives for only 30 days. Eggs hatch in 5–7 days. As many as 10 generations may occur each year. The young look similar to the adults, but newly hatched young have only six legs and do not possess the characteristic dark spots on the back. Reproduction of the two-spotted spider mite is favored by hot, dry conditions, so serious damage is likely to occur in mid-July to September. The spruce spider mite is most active durng cooler weather in Spring and Fall.
Integrated Pest Management Strategies
1. Knock mites off plants with water. Spraying with a strong stream of water (particularly the undersides of leaves) will provide some control. Spray plants frequently to control future buildups. For severe infestations, affected plants or plant parts can be removed and destroyed. There are several natural predators that feed on spider mites. The use of chemical insecticides to control other garden pests can result in the death of these beneficial insects and a subsequent increase in the population of spider mites.
2. Use insecticidal soap. Insecticidal soaps specially formulated to kill insects and not damage plants are effective if used frequently until the problem is under control.
3. Use superior horticultural oil sprays. Highly refined oils sold as superior or horticultural oils are also very effective in controlling spider mites. The oil suffocates the mites. Unlike dormant oils, these oils are highly refined and under proper conditions, can be applied to plant foliage without damage. Follow label directions to avoid damage to some plants that may be sensitive. Superior oils are considered nontoxic and are less likely to kill beneficial insects.
4. Use chemical insecticides or miticides. A very safe product made from the seeds of a tropical tree is called Neem. It is commercially available under the name Margosan-O. Other chemical controls include malathion, bifenthrin, cyfluthrin, and kelthane. Be sure to follow all label directions when using pesticides. Many pesticides are very harmful to bees and fish when used improperly.
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文章
Dummer. ゛☀
2017年09月16日
Numerous species of leafhoppers and planthoppers are found in Missouri, and many of them have a broad host list (for example, the potato leafhopper, Empoasca fabae, has over 100 host plants). They feed on foliage and shoots of many different plant species by piercing the plant cells and sucking out the contents. The damage that results from feeding depends on the host plant and the specific hopper. Only a few species of hoppers transmit pathogens such as those that cause curly top virus and aster yellows. Adult hoppers are excellent short-distance jumpers when disturbed, and they can be pests when found in high numbers.
Symptoms and Diagnosis
Hoppers are agile insects that can move with equal ease either forwards, backwards, or sideways like a crab. The crab-like motion distinguishes hoppers from most other insects. In addition, they can hop to escape danger or to move to another host plant.
Feeding damage from some species causes small white spots (stippling) to appear on the upper leaf surface, usually beginning near the leaf midrib.
Stippled areas can unite into larger whitish blotches on mature leaves. With some plants, feeding damage causes a drying and yellowing (or browning) of leaf margins, and possibly the whole leaf. Some leafhopper species cause curling or stunting of terminal leaves with their feeding. Another sign of feeding is the presence of tiny varnish-like spots of excrement on the underside of leaves. Also, check under leaves for white, papery cast skins that remain from the molting process.
The lacebug is another insect that causes stippling from feeding and leaves dark droplets of varnish-like excrement on the underside of leaves. Distinguishing lacebugs from leafhoppers is easy:
Lacebugs have a lacy pattern on their upper side, they don't jump or run sideways, and they are about half as broad as they are long. Yet another pest that can cause stippling is the spider mite. Check under leaves for the webbing left by spider mites (leafhoppers don't leave webbing).
Life Cycle
Adults of most species of leafhopper range between 1/8 to 1/4 inch long. They are slender and frequently have an angular, pointed head. Coloration depends on species, but generally leafhoppers are shades of green, brown, or yellow and are often mottled. Nymphs (immatures) look similar to the adults except that the nymphs are smaller and don't have wings. Nymphs typically feed on the underside of leaves, where the humidity is higher and they are more protected from predators.
Leafhoppers have several generations each year. Some species migrate south in winter and return north with late spring weather.
Integrated Pest Management Strategies
1. Live with the pests. Because of their mobility and abundance, leafhoppers are not easy to control. However, leafhoppers are seldom present in large enough numbers to seriously injure plants. In addition, leafhoppers have many natural enemies, including lady beetles, lacewings, damsel bugs, and spiders. They are also subject to diseases and parasites that help keep their numbers down under most conditions.
2. Use row covers. Floating row covers or netting can be placed over plants early in summer to exclude leafhoppers. Remove row covers when the plants begin to flower.
3. Monitor with sticky traps. Many leafhoppers are attracted to yellow sticky traps which should be placed close to the foliage of the crop. Populations can be monitored with sticky traps and low populations can be managed using these traps.
4. Apply insecticidal soap. Insecticidal soap can control leafhoppers if applied when the insects are small. The immature leafhoppers are usually found on the underside of leaves so be sure to spray there also.
5. Apply insecticides. Other insecticides available for leafhopper control include botanical pyrethrins, carbaryl (Sevin), malathion, bifenthrin, cyfluthrin, bendiocarb (Turcam, Closure), disulfoton (Disyston), and acephate (Orthene). In general, these are most effective on the immature leafhoppers because they can't escape as well as the adults and are typically more susceptible to chemicals.
Symptoms and Diagnosis
Hoppers are agile insects that can move with equal ease either forwards, backwards, or sideways like a crab. The crab-like motion distinguishes hoppers from most other insects. In addition, they can hop to escape danger or to move to another host plant.
Feeding damage from some species causes small white spots (stippling) to appear on the upper leaf surface, usually beginning near the leaf midrib.
Stippled areas can unite into larger whitish blotches on mature leaves. With some plants, feeding damage causes a drying and yellowing (or browning) of leaf margins, and possibly the whole leaf. Some leafhopper species cause curling or stunting of terminal leaves with their feeding. Another sign of feeding is the presence of tiny varnish-like spots of excrement on the underside of leaves. Also, check under leaves for white, papery cast skins that remain from the molting process.
The lacebug is another insect that causes stippling from feeding and leaves dark droplets of varnish-like excrement on the underside of leaves. Distinguishing lacebugs from leafhoppers is easy:
Lacebugs have a lacy pattern on their upper side, they don't jump or run sideways, and they are about half as broad as they are long. Yet another pest that can cause stippling is the spider mite. Check under leaves for the webbing left by spider mites (leafhoppers don't leave webbing).
Life Cycle
Adults of most species of leafhopper range between 1/8 to 1/4 inch long. They are slender and frequently have an angular, pointed head. Coloration depends on species, but generally leafhoppers are shades of green, brown, or yellow and are often mottled. Nymphs (immatures) look similar to the adults except that the nymphs are smaller and don't have wings. Nymphs typically feed on the underside of leaves, where the humidity is higher and they are more protected from predators.
Leafhoppers have several generations each year. Some species migrate south in winter and return north with late spring weather.
Integrated Pest Management Strategies
1. Live with the pests. Because of their mobility and abundance, leafhoppers are not easy to control. However, leafhoppers are seldom present in large enough numbers to seriously injure plants. In addition, leafhoppers have many natural enemies, including lady beetles, lacewings, damsel bugs, and spiders. They are also subject to diseases and parasites that help keep their numbers down under most conditions.
2. Use row covers. Floating row covers or netting can be placed over plants early in summer to exclude leafhoppers. Remove row covers when the plants begin to flower.
3. Monitor with sticky traps. Many leafhoppers are attracted to yellow sticky traps which should be placed close to the foliage of the crop. Populations can be monitored with sticky traps and low populations can be managed using these traps.
4. Apply insecticidal soap. Insecticidal soap can control leafhoppers if applied when the insects are small. The immature leafhoppers are usually found on the underside of leaves so be sure to spray there also.
5. Apply insecticides. Other insecticides available for leafhopper control include botanical pyrethrins, carbaryl (Sevin), malathion, bifenthrin, cyfluthrin, bendiocarb (Turcam, Closure), disulfoton (Disyston), and acephate (Orthene). In general, these are most effective on the immature leafhoppers because they can't escape as well as the adults and are typically more susceptible to chemicals.
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文章
Dummer. ゛☀
2017年09月16日
The iris borer causes more damage to iris plants than any other insect. Feeding of the borer larva opens the rhizome to attack by soft rot that can quickly turn rhizomes into foul-smelling mush. A healthy bed of iris can be destroyed quickly.
Symptoms and Diagnosis
Damage is typified by dark streaks, water-soaked areas, and ragged edges on young leaves in May and June, caused by feeding of the young larvae. As the larvae feed, they move down into the rhizome where they continue feeding. Soft rot can set in, causing leaves to yellow and fall over and rhizomes may become soft and foul-smelling. Cutting open the rhizome will reveal the borer, a 1- to 2- inch, fat-bodied, pink larva with a brown head.
Life Cycle
Adult moths emerge from the soil in August and September, mate, and deposit eggs on dead iris leaves. The crevices of dried and crinkled leaves or rolled leaf areas make a good place to lay their eggs. The base of leaves and other plant debris is the wintering place of the eggs. Eggs are laid in groups of 3–5 or more; a single female moth may deposit 1000 eggs before dying. Moths are typical millers— dark gray to brown, with a wingspan of about 2 inches. There is only one generation per year.
The eggs overwinter in the plant material and hatch in April or early May as the new iris leaves are expanding. The small, young larvae crawl up onto the new iris leaves and make tiny pinpoint holes as they enter. Once the larvae enter the foliage, they act as leafminers, tunneling to the base of the leaves throughout the spring. By early to mid-July the larvae reach the soil area and tunnel into the rhizomes.
In the rhizome, the larvae grow to be 1 to 2 inches in length. In late July to early August, the iris borer larvae move from the rhizomes into the soil to pupate. The pupa is a non-feeding transition stage between the larva and the adult moth. Pupae are dark brown to black and are usually found in the top 2 inches of soil. After two to three weeks in the pupa stage, the iris borer moth emerges. The adult brown moths emerge in late August and September to mate, lay eggs, and repeat the cycle.
Integrated Pest Management Strategies
1. Sanitation. The main key to iris borer prevention is removal and destruction of the previous year’s dead foliage before April 1. This sanitation practice will reduce the problem by destroying overwintering eggs in the residues. This is best done in spring. Peel off the dead foliage down to the rhizome.
2. Inspect bed. If signs of borers are apparent, dig the rhizomes after blooming is completed. Inspect them carefully, cut out damaged ones, and replant. During the spring, inspect the leaves for signs of borers larvae chewing and pinch down the leaves to kill any larvae that may be inside.
3. Precaution. An insecticide containing pyrethrum spread or sprayed around the base of plants in the spring may help in destroying the newly hatched larvae before they have a chance to enter leaves.
4. Insecticides. If the problem is severe, insecticides are available to help combat borers. When iris leaves are 3–4 inches long, begin spraying at two-week intervals, using azadirachtin (Bio-Neem, Margosan-O), endosulfan (Thiodan), or methyl nonyl ketone. These are available under various trade names at nurseries and garden centers. Always follow label directions and read the entire label before using.
5. Replanting. When resetting your iris beds, it is important to trim away damaged or rotted areas on the rhizomes. To eliminate soft rots caused by bacteria, cut off the damaged parts of the rhizomes and dip the undamaged portions in a solution of 1–part household chlorine bleach and 9 parts of water.
Symptoms and Diagnosis
Damage is typified by dark streaks, water-soaked areas, and ragged edges on young leaves in May and June, caused by feeding of the young larvae. As the larvae feed, they move down into the rhizome where they continue feeding. Soft rot can set in, causing leaves to yellow and fall over and rhizomes may become soft and foul-smelling. Cutting open the rhizome will reveal the borer, a 1- to 2- inch, fat-bodied, pink larva with a brown head.
Life Cycle
Adult moths emerge from the soil in August and September, mate, and deposit eggs on dead iris leaves. The crevices of dried and crinkled leaves or rolled leaf areas make a good place to lay their eggs. The base of leaves and other plant debris is the wintering place of the eggs. Eggs are laid in groups of 3–5 or more; a single female moth may deposit 1000 eggs before dying. Moths are typical millers— dark gray to brown, with a wingspan of about 2 inches. There is only one generation per year.
The eggs overwinter in the plant material and hatch in April or early May as the new iris leaves are expanding. The small, young larvae crawl up onto the new iris leaves and make tiny pinpoint holes as they enter. Once the larvae enter the foliage, they act as leafminers, tunneling to the base of the leaves throughout the spring. By early to mid-July the larvae reach the soil area and tunnel into the rhizomes.
In the rhizome, the larvae grow to be 1 to 2 inches in length. In late July to early August, the iris borer larvae move from the rhizomes into the soil to pupate. The pupa is a non-feeding transition stage between the larva and the adult moth. Pupae are dark brown to black and are usually found in the top 2 inches of soil. After two to three weeks in the pupa stage, the iris borer moth emerges. The adult brown moths emerge in late August and September to mate, lay eggs, and repeat the cycle.
Integrated Pest Management Strategies
1. Sanitation. The main key to iris borer prevention is removal and destruction of the previous year’s dead foliage before April 1. This sanitation practice will reduce the problem by destroying overwintering eggs in the residues. This is best done in spring. Peel off the dead foliage down to the rhizome.
2. Inspect bed. If signs of borers are apparent, dig the rhizomes after blooming is completed. Inspect them carefully, cut out damaged ones, and replant. During the spring, inspect the leaves for signs of borers larvae chewing and pinch down the leaves to kill any larvae that may be inside.
3. Precaution. An insecticide containing pyrethrum spread or sprayed around the base of plants in the spring may help in destroying the newly hatched larvae before they have a chance to enter leaves.
4. Insecticides. If the problem is severe, insecticides are available to help combat borers. When iris leaves are 3–4 inches long, begin spraying at two-week intervals, using azadirachtin (Bio-Neem, Margosan-O), endosulfan (Thiodan), or methyl nonyl ketone. These are available under various trade names at nurseries and garden centers. Always follow label directions and read the entire label before using.
5. Replanting. When resetting your iris beds, it is important to trim away damaged or rotted areas on the rhizomes. To eliminate soft rots caused by bacteria, cut off the damaged parts of the rhizomes and dip the undamaged portions in a solution of 1–part household chlorine bleach and 9 parts of water.
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Dummer. ゛☀
2017年09月16日
Cyclamen and broad mites are microscopic mites (less than 0.02mm in length) that deform and distort the growing tips of plants that can result in stunted tips, curled leaves and lack of flowering. Cyclamen mites can be a pest of garden strawberry plants and both can be serious pests of a wide range of plants including: African violet, cyclamen, begonia, snapdragon, impatien, gerbera, ivy, and many indoor tropical plants.
Symptoms and Diagnosis
The mites are generally not detected until after they have caused significant damage and then only with the aid of a dissecting microscope. Hand lenses are usually not powerful enough to see these small mites. Mites are closely related to spiders and likewise adults have 4 pairs of legs. Larvae, however, have only 3 pairs.
Cyclamen mites are usually greenish and transparent and less than 1 mm in size. Their eggs are smooth and more apt to be found hidden in folds of plant tissue. They like to hide in buds or tips of new growth. They avoid light and prefer high humidity and cool (60 degrees F.) temperatures. Their feeding results in stunted growth with leaves generally curling upward. Leaves become stiffened and brittle (black in the case of delphiniums) and flowers are deformed or reduced.
Broad mites are smaller than cyclamen mites, broader, and are faster moving. Adult females are straw colored. Broad mites have a white stripe down their back, but the easiest way to differentiate the two may be by their eggs. Broad mites eggs have many small white bumps on them and are usually observed in more open locations. Typically adults cause deformed shoots and leaves, which usually curl downward, and reduced flowering. Bronzing or purpling of the leaves commonly occurs on the underside of leaves where the mites feed. Broad mites reproduce most prolifically at temperatures between 70 and 80 degrees F.
Lifecycle
Cyclamen mites can complete their lifecycle in only 1 to 3 weeks depending upon conditions. Adults can overwinter out of doors as far north as Canada in protected locations and complete many generations a year.
Broad mites can complete their lifecycle in only one week and also have a resting, pupal stage. They can overwinter in greenhouses or on indoor plants but is doubtful they can overwinter out or doors in Missouri. Meaning that each year new infestations out of doors develop from plants that have been overwintered indoors or from infested plants obtained from a nursery or garden center.
Integrated Pest Management
1. Dispose of infested plants. Since these mites can be difficult to control and reproduce rapidly, disposing of infested plants is often wise.
2. Sanitation. Examine newly purchases plant in the spring and reject them if they have curled or deformed tips and shoots that may be signs of mites.
3. Heat treatment. Cyclamen and broad mites are heat sensitive and can be killed if immersed in 110 degree F water for 30 minutes. These temperatures are generally low enough to cause little damage to most plants but water temperature must be maintained properly and the whole plant, pot and all, needs to be immersed. Removing heavily infested shoots first may make this process easier.
4. Treat with miticidal/ insecticidal soap or horticultural oil. To be effective the spray must completely cover the insects so apply liberally and make sure the spray reaches under leaves and into shoot tips where the mites hide.
5. Use chemical sprays. Dicofol (Kelthane) a broad-spectrum miticide can give good control. Follow label instructions.
Symptoms and Diagnosis
The mites are generally not detected until after they have caused significant damage and then only with the aid of a dissecting microscope. Hand lenses are usually not powerful enough to see these small mites. Mites are closely related to spiders and likewise adults have 4 pairs of legs. Larvae, however, have only 3 pairs.
Cyclamen mites are usually greenish and transparent and less than 1 mm in size. Their eggs are smooth and more apt to be found hidden in folds of plant tissue. They like to hide in buds or tips of new growth. They avoid light and prefer high humidity and cool (60 degrees F.) temperatures. Their feeding results in stunted growth with leaves generally curling upward. Leaves become stiffened and brittle (black in the case of delphiniums) and flowers are deformed or reduced.
Broad mites are smaller than cyclamen mites, broader, and are faster moving. Adult females are straw colored. Broad mites have a white stripe down their back, but the easiest way to differentiate the two may be by their eggs. Broad mites eggs have many small white bumps on them and are usually observed in more open locations. Typically adults cause deformed shoots and leaves, which usually curl downward, and reduced flowering. Bronzing or purpling of the leaves commonly occurs on the underside of leaves where the mites feed. Broad mites reproduce most prolifically at temperatures between 70 and 80 degrees F.
Lifecycle
Cyclamen mites can complete their lifecycle in only 1 to 3 weeks depending upon conditions. Adults can overwinter out of doors as far north as Canada in protected locations and complete many generations a year.
Broad mites can complete their lifecycle in only one week and also have a resting, pupal stage. They can overwinter in greenhouses or on indoor plants but is doubtful they can overwinter out or doors in Missouri. Meaning that each year new infestations out of doors develop from plants that have been overwintered indoors or from infested plants obtained from a nursery or garden center.
Integrated Pest Management
1. Dispose of infested plants. Since these mites can be difficult to control and reproduce rapidly, disposing of infested plants is often wise.
2. Sanitation. Examine newly purchases plant in the spring and reject them if they have curled or deformed tips and shoots that may be signs of mites.
3. Heat treatment. Cyclamen and broad mites are heat sensitive and can be killed if immersed in 110 degree F water for 30 minutes. These temperatures are generally low enough to cause little damage to most plants but water temperature must be maintained properly and the whole plant, pot and all, needs to be immersed. Removing heavily infested shoots first may make this process easier.
4. Treat with miticidal/ insecticidal soap or horticultural oil. To be effective the spray must completely cover the insects so apply liberally and make sure the spray reaches under leaves and into shoot tips where the mites hide.
5. Use chemical sprays. Dicofol (Kelthane) a broad-spectrum miticide can give good control. Follow label instructions.
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文章
Dummer. ゛☀
2017年09月16日
Millipedes and centipedes are not insects but distant relatives of lobsters, crayfish and shrimp. They are land dwellers, but they prefer moist areas with high humidity. They carry no diseases to man, animals or plants. They are considered more as nuisances than destructive pests, and are beneficial in the garden.
Millipedes
Millipedes, commonly called “thousand-leggers”, have elongated, cylindrical bodies with 25+ pairs of short legs, two pairs per body segment. The legs are held beneath the body and appear to ripple in waves as they move. The head is rounded and projects two short antennae. The body color ranges from light brown to black. Millipedes move slowly and coil up when disturbed or dead. They range in length from a half inch to six inches. They are not venomous but possess glands that produce an irritating, foul-smelling fluid. They feed on decaying vegetable matter.
Millipedes migrate in great numbers when it is too hot or too cold, too wet or too dry. They may migrate indoors, but they do not reproduce indoors. They are considered beneficial in the garden because they enrich the soil by breaking down decaying vegetation.
Centipedes
Centipedes, commonly called “hundred-leggers”, have elongated, flattened bodies with fewer than 25 pairs of long legs, one pair per segment. The legs project laterally from the body. The head is flattened and projects two long antennae. Just behind the head are the jaws that contain venom glands used to paralyze their prey. Centipedes are predators, feeding on insects and spiders. They move rapidly and never coil up their bodies. They are yellow to brown in color and just over an inch in length.
Centipede populations do not increase in great numbers. They occasionally enter homes where they prefer dark, moist areas. The house centipede (Scutigera) does enter homes and may reproduce indoors. Centipedes are considered beneficial in the garden and home because they control insect populations
Life Cycle
Millipedes
Millipede adults overwinter in the soil. In spring the female lays 20-300 eggs in the soil. The first stage larvae have only three pairs of legs on three body segments. The larvae go through 7—10 development stages and become adults in 2—5 years. Adults live for several years.
Centipedes
Centipede adults overwinter in secluded, moist places. In spring and summer females lay eggs in damp soil. Some species are born complete and others add segments and legs as they grow. They mature in 2—3 years and live up to six years.
Integrated Pest Management Strategies
1. Control Outdoors. Millipedes and centipedes are considered beneficial outdoors; therefore, encourage their presence. To help prevent them from moving indoors: remove organic matter in contact with the house foundation, minimize watering near building foundations, clean up piles of rocks, leaves, compost and general refuse near the building, and make sure doors and windows fit snugly (caulk crevices). Pesticides can be used to treat the foundation and an adjacent three-foot ground strip with dust or aerosol spray labeled for these organisms. Follow label directions precisely.
2. Control Indoors. Hand pick or vacuum to control individuals. Reduce moisture and remove hiding places, or place sticky traps against walls near entryways. You can also use a pesticides if populations are high or persistent. A contact or aerosol sprays containing pyrethrins or carbaryl can be used. Treat baseboards, cracks and crevices. Follow label directions precisely.
Millipedes
Millipedes, commonly called “thousand-leggers”, have elongated, cylindrical bodies with 25+ pairs of short legs, two pairs per body segment. The legs are held beneath the body and appear to ripple in waves as they move. The head is rounded and projects two short antennae. The body color ranges from light brown to black. Millipedes move slowly and coil up when disturbed or dead. They range in length from a half inch to six inches. They are not venomous but possess glands that produce an irritating, foul-smelling fluid. They feed on decaying vegetable matter.
Millipedes migrate in great numbers when it is too hot or too cold, too wet or too dry. They may migrate indoors, but they do not reproduce indoors. They are considered beneficial in the garden because they enrich the soil by breaking down decaying vegetation.
Centipedes
Centipedes, commonly called “hundred-leggers”, have elongated, flattened bodies with fewer than 25 pairs of long legs, one pair per segment. The legs project laterally from the body. The head is flattened and projects two long antennae. Just behind the head are the jaws that contain venom glands used to paralyze their prey. Centipedes are predators, feeding on insects and spiders. They move rapidly and never coil up their bodies. They are yellow to brown in color and just over an inch in length.
Centipede populations do not increase in great numbers. They occasionally enter homes where they prefer dark, moist areas. The house centipede (Scutigera) does enter homes and may reproduce indoors. Centipedes are considered beneficial in the garden and home because they control insect populations
Life Cycle
Millipedes
Millipede adults overwinter in the soil. In spring the female lays 20-300 eggs in the soil. The first stage larvae have only three pairs of legs on three body segments. The larvae go through 7—10 development stages and become adults in 2—5 years. Adults live for several years.
Centipedes
Centipede adults overwinter in secluded, moist places. In spring and summer females lay eggs in damp soil. Some species are born complete and others add segments and legs as they grow. They mature in 2—3 years and live up to six years.
Integrated Pest Management Strategies
1. Control Outdoors. Millipedes and centipedes are considered beneficial outdoors; therefore, encourage their presence. To help prevent them from moving indoors: remove organic matter in contact with the house foundation, minimize watering near building foundations, clean up piles of rocks, leaves, compost and general refuse near the building, and make sure doors and windows fit snugly (caulk crevices). Pesticides can be used to treat the foundation and an adjacent three-foot ground strip with dust or aerosol spray labeled for these organisms. Follow label directions precisely.
2. Control Indoors. Hand pick or vacuum to control individuals. Reduce moisture and remove hiding places, or place sticky traps against walls near entryways. You can also use a pesticides if populations are high or persistent. A contact or aerosol sprays containing pyrethrins or carbaryl can be used. Treat baseboards, cracks and crevices. Follow label directions precisely.
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文章
Dummer. ゛☀
2017年09月16日
Frost heaving can cause plants to rise up out of the ground as these hens and chicks (Sempervivum) did.
Cold-hardy perennials can be damaged by winter weather. Frost heaving is the usual culprit. Wide temperature fluctuations, with repeated cycles of freezing and thawing, cause the water in the soil to expand and contract. These repeated expansions and contractions push and turn plants and their roots. The result is heaving of the crowns. They are pushed up out of the soil breaking some roots and exposing other roots above soil level. The elevated crowns and roots are exposed to cold temperatures and drying winds. They may be seriously damaged, stunted or killed.
Perennials with shallow root systems (strawberries, heuchera, scabiosa, leucanthemum, galliardia, bergenia) or those that have been planted recently and have not had time to establish adequate root systems are prone to frost heaving.
Integrated Pest Management Strategies
1. Controlling frost heaving starts with well drained planting beds. Both surface and subsurface drainage is essential to prevent water from pooling in planted beds. Soggy ground will freeze and thaw repeatedly and susceptible plants will heave. The addition of organic material when the beds are prepared helps loosen soil and promotes good soil drainage.
2. Plant early in the fall. Planting perennials at least 6 weeks before the first autumn frost date gives the plants time to establish adequate root systems to anchor themselves.
3. Mulch. Mulching with organic material (compost, ground leaves, straw, or pine needles) will help moderate soil temperatures reducing heaving of root systems. The mulch should be applied after a hard frost, and at a depth of 4 inches. Excess mulch can lead to soggy ground and rodent infestations. Avoid burying the plant’s crown as the mulch is put down.
4. Monitor the plants. Keep a careful eye on susceptible plants. The mulch can hide an exposed, heaved crown. When a problem is found, cover the exposed roots with a layer of soil and re-apply mulch.
Cold-hardy perennials can be damaged by winter weather. Frost heaving is the usual culprit. Wide temperature fluctuations, with repeated cycles of freezing and thawing, cause the water in the soil to expand and contract. These repeated expansions and contractions push and turn plants and their roots. The result is heaving of the crowns. They are pushed up out of the soil breaking some roots and exposing other roots above soil level. The elevated crowns and roots are exposed to cold temperatures and drying winds. They may be seriously damaged, stunted or killed.
Perennials with shallow root systems (strawberries, heuchera, scabiosa, leucanthemum, galliardia, bergenia) or those that have been planted recently and have not had time to establish adequate root systems are prone to frost heaving.
Integrated Pest Management Strategies
1. Controlling frost heaving starts with well drained planting beds. Both surface and subsurface drainage is essential to prevent water from pooling in planted beds. Soggy ground will freeze and thaw repeatedly and susceptible plants will heave. The addition of organic material when the beds are prepared helps loosen soil and promotes good soil drainage.
2. Plant early in the fall. Planting perennials at least 6 weeks before the first autumn frost date gives the plants time to establish adequate root systems to anchor themselves.
3. Mulch. Mulching with organic material (compost, ground leaves, straw, or pine needles) will help moderate soil temperatures reducing heaving of root systems. The mulch should be applied after a hard frost, and at a depth of 4 inches. Excess mulch can lead to soggy ground and rodent infestations. Avoid burying the plant’s crown as the mulch is put down.
4. Monitor the plants. Keep a careful eye on susceptible plants. The mulch can hide an exposed, heaved crown. When a problem is found, cover the exposed roots with a layer of soil and re-apply mulch.
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文章
Dummer. ゛☀
2017年09月16日
Newly planted annuals and perennials need careful attention to establish and develop properly. Many factors can result in poor establishment or death. Plants that have failed to establish can often be recognized when you tug on a dead, dying or ailing plant and it comes out of the ground with a root ball much the same as when it was planted having failed to send new roots into the surrounding soil. Here are few of the major points to watch to help your plants become well established after planting.
1. Improper watering. Improper watering is probably the most common reason why a plant dies before it becomes established. Newly planted plants have a small root system, which can dry out very quickly. Be sure and water plants well just after planting and then monitor closely. If the root ball is allowed to dry out the young plant will be severely injured and may never recover. On the other hand, if the root ball is kept too wet, the plant’s roots may rot. Maintaining the correct balance is imperative for the first few weeks to promote healthy root development into the surrounding soil.
2. Plants with small root balls and a lot of foliage can dry out very quickly in hot weather. They may need watering every couple of days when first planted, but the goal should be to extend the time between watering as the plant becomes established. A single severe drying event can kill new transplants! Mulching around young plants can help keep soil moisture more uniform. Keep mulch away from the crown of plants, however, as doing so can encourage crown rots by retaining too much moisture at the base of the plant. Mulch should not touch the crown of the plant.
3. Wrong location. It should be obvious that a plant that needs full sun should not be planted in the shade or vice versa, but still people push the limits. Shade plants grown in too much sun may not establish or just burn up. Sun plants growing in too much shade may lose vigor and eventually die. Plants that need a well-drained soil may also die quickly if planted in wet soils where they are susceptible to root rots.
4. Excess summer heat. Certain plants best adapted to climates with cool summers may not perform well in locations with hot, humid summers. Poor growth, yellowing or bleached foliage, and dieback may all be signs that your plant is suffering from heat stress.
5. Mechanical damage to stems. The stems of young plants can be very vulnerable to damage during planting. Use care when planting so you don't create wounds where fungi or bacteria can enter and rot the crown of the plant.
1. Improper watering. Improper watering is probably the most common reason why a plant dies before it becomes established. Newly planted plants have a small root system, which can dry out very quickly. Be sure and water plants well just after planting and then monitor closely. If the root ball is allowed to dry out the young plant will be severely injured and may never recover. On the other hand, if the root ball is kept too wet, the plant’s roots may rot. Maintaining the correct balance is imperative for the first few weeks to promote healthy root development into the surrounding soil.
2. Plants with small root balls and a lot of foliage can dry out very quickly in hot weather. They may need watering every couple of days when first planted, but the goal should be to extend the time between watering as the plant becomes established. A single severe drying event can kill new transplants! Mulching around young plants can help keep soil moisture more uniform. Keep mulch away from the crown of plants, however, as doing so can encourage crown rots by retaining too much moisture at the base of the plant. Mulch should not touch the crown of the plant.
3. Wrong location. It should be obvious that a plant that needs full sun should not be planted in the shade or vice versa, but still people push the limits. Shade plants grown in too much sun may not establish or just burn up. Sun plants growing in too much shade may lose vigor and eventually die. Plants that need a well-drained soil may also die quickly if planted in wet soils where they are susceptible to root rots.
4. Excess summer heat. Certain plants best adapted to climates with cool summers may not perform well in locations with hot, humid summers. Poor growth, yellowing or bleached foliage, and dieback may all be signs that your plant is suffering from heat stress.
5. Mechanical damage to stems. The stems of young plants can be very vulnerable to damage during planting. Use care when planting so you don't create wounds where fungi or bacteria can enter and rot the crown of the plant.
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Dummer. ゛☀
2017年09月16日
Leaf scorch may occur on any species of tree or shrub as well as herbaceous plants. It is a widespread noninfectious disease or disorder. Scorch most often occurs following prolonged periods of dry, windy weather or bright sunshine when the roots are unable to supply water to the foliage as rapidly as it is lost by transpiration from the leaves. Unfavorable locations, such as sandy or gravelly soil, near obstructions or pavement that restrict root growth, or exposed windy slopes usually promote scorch. Anything that affects the plant’s ability to take up water, including insect and disease problems, can result in leaf scorch. Herbicides and pesticides may also contribute to scorch. Do not spray on windy days to eliminate drift problems and do not allow mist to settle onto trees.
In mild cases of leaf scorch, the leaves remain attached, and little damage results. In more severe cases, plants may drop many of their leaves prematurely, although such plants do not die. Where leaf scorch occurs each year, such annual stress will gradually weaken the plant, making it more susceptible to insects and diseases.
Symptoms and Diagnosis
Browning of leaf margins and/or yellowing or darkening of the areas between the main leaf veins are symptoms of leaf scorch. Due to environmental causes, leaves may dry, turn brown, and become brittle. Look for damage to trees and shrubs on the upper portion on the sunny, southern side and on the windy side. Premature dropping of leaves and twig dieback may occur during the late summer. Symptoms usually appear after drying winds in conjunction with periods of hot, dry weather.
Leaf scorch on narrow leaf evergreens appears as brown or purple brown discoloration of the needle tips. If unfavorable conditions become more severe, browning of needles increases. This should not be confused with the browning and shedding of older interior needles. Scorch may result from hot, dry weather in summer or from strong, dry winter winds when the ground is frozen. Symptoms may not become apparent for a month or more after the initial injury.
Winter leaf scorch in evergreen plants usually appears as two long, brown areas paralleling the main leaf vein.
Life Cycle
Although plants can experience scorch with no insects or disease pathogens involved, insect and disease damage can also affect the plant’s uptake of water. In some cases, insect damage such as leafhopper (hopper burn) or specific scorch diseases caused by fungi or bacteria can produce similar symptoms. Scorch can also reduce the health of a plant making it more susceptible to attack by insects and diseases.
Integrated Pest Management Strategies
1.Water when needed and maintain plant vigor. Plant in a fertile, well-drained soil at the same depth the plants grew in at the nursery and with an adequate supply of organic matter. Soil should be moist to a depth of 10 to 12 inches after a thorough watering. This should be done about once weekly. It is very important for the trees, especially broadleaf and needled evergreens, to be well watered going into the winter period. Water during this period if seasonal rains are not adequate or during the winter when the soil is not frozen. Annuals and perennials require more frequent watering than most trees and shrubs.
2. Fertilize. Fertilize plants in early spring based on a soil test and the directions printed on the fertilizer container. Nitrogen should be applied annually based on the area to be fertilized, the type of plant, and the diameter of the trunk. Do not fertilize with nitrogen in the late fall as it may cause new soft growth easily damaged by cold weather.
3. Mulch. Organic mulches (pine needles, wood chips, composted leaves, pine bark, cypress mulch) can help retain moisture during the summer and fall droughts. In the winter this mulch prevents the alternate freezing and thawing of the soil. Mulch will also cool the soil in summer.
4. Screens. Screens may be used to protect trees and plants in areas exposed to wind and sun, but it is best not to plant tender plants in these exposures.
5. Exposure. Other factors which can result in scorch are excessive fertilizer, deicing salt, herbicide, dog urine, trash fires, leaking sewer or gas mains, girdling roots or strangling wires, vehicle exhaust, and heat reflected from buildings. Elimination of the exposure to these elements is the only correction.
6. Physical hazards. Avoid root injury when digging near trees and shrubs. Care should be taken to not injure the bark and roots when using lawnmowers, weed whips, and edging tools.
In mild cases of leaf scorch, the leaves remain attached, and little damage results. In more severe cases, plants may drop many of their leaves prematurely, although such plants do not die. Where leaf scorch occurs each year, such annual stress will gradually weaken the plant, making it more susceptible to insects and diseases.
Symptoms and Diagnosis
Browning of leaf margins and/or yellowing or darkening of the areas between the main leaf veins are symptoms of leaf scorch. Due to environmental causes, leaves may dry, turn brown, and become brittle. Look for damage to trees and shrubs on the upper portion on the sunny, southern side and on the windy side. Premature dropping of leaves and twig dieback may occur during the late summer. Symptoms usually appear after drying winds in conjunction with periods of hot, dry weather.
Leaf scorch on narrow leaf evergreens appears as brown or purple brown discoloration of the needle tips. If unfavorable conditions become more severe, browning of needles increases. This should not be confused with the browning and shedding of older interior needles. Scorch may result from hot, dry weather in summer or from strong, dry winter winds when the ground is frozen. Symptoms may not become apparent for a month or more after the initial injury.
Winter leaf scorch in evergreen plants usually appears as two long, brown areas paralleling the main leaf vein.
Life Cycle
Although plants can experience scorch with no insects or disease pathogens involved, insect and disease damage can also affect the plant’s uptake of water. In some cases, insect damage such as leafhopper (hopper burn) or specific scorch diseases caused by fungi or bacteria can produce similar symptoms. Scorch can also reduce the health of a plant making it more susceptible to attack by insects and diseases.
Integrated Pest Management Strategies
1.Water when needed and maintain plant vigor. Plant in a fertile, well-drained soil at the same depth the plants grew in at the nursery and with an adequate supply of organic matter. Soil should be moist to a depth of 10 to 12 inches after a thorough watering. This should be done about once weekly. It is very important for the trees, especially broadleaf and needled evergreens, to be well watered going into the winter period. Water during this period if seasonal rains are not adequate or during the winter when the soil is not frozen. Annuals and perennials require more frequent watering than most trees and shrubs.
2. Fertilize. Fertilize plants in early spring based on a soil test and the directions printed on the fertilizer container. Nitrogen should be applied annually based on the area to be fertilized, the type of plant, and the diameter of the trunk. Do not fertilize with nitrogen in the late fall as it may cause new soft growth easily damaged by cold weather.
3. Mulch. Organic mulches (pine needles, wood chips, composted leaves, pine bark, cypress mulch) can help retain moisture during the summer and fall droughts. In the winter this mulch prevents the alternate freezing and thawing of the soil. Mulch will also cool the soil in summer.
4. Screens. Screens may be used to protect trees and plants in areas exposed to wind and sun, but it is best not to plant tender plants in these exposures.
5. Exposure. Other factors which can result in scorch are excessive fertilizer, deicing salt, herbicide, dog urine, trash fires, leaking sewer or gas mains, girdling roots or strangling wires, vehicle exhaust, and heat reflected from buildings. Elimination of the exposure to these elements is the only correction.
6. Physical hazards. Avoid root injury when digging near trees and shrubs. Care should be taken to not injure the bark and roots when using lawnmowers, weed whips, and edging tools.
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文章
Dummer. ゛☀
2017年09月16日
Hail can severely damage all plants. The severity of the damage depends on the size of the hailstones and the time of the year that the hailstorm occurs. The later in the growing season that hail damage occurs the less time plants have to recover and store energy for the winter.
Symptoms and Diagnosis
On annuals and perennials leaves, stems and flowers may be shredded, torn and knocked off. On trees and shrubs leaves, twigs and branches may be tattered, split and broken. Fruit may be pitted and knocked to the ground. The scars from hail damage to trees occur on the upper side of branches and on the side of the trunk facing the storm. The tree may take a very long time to recover. The damage increases the vulnerability of the tree to decay causing fungi and insect activity.
Integrated Pest Management Strategies
1. Evaluate damage. Assess the damage to the plants and estimate how long they have left to recover from the damage before the onset of winter.
2. Cleanup. Severely damaged trees and shrubs with broken branches should have them removed promptly. Less severe wounds may slowly heal naturally over a period of time. Damaged fruit should be removed. Do not fertilize hail damaged trees.
3. Fertilize. If the damage is early in the growing season, annuals and perennials may benefit from a light application of fertilizer. Immediately remove any damaged leaves from these plants.
4. Replace. Annuals and perennials that do not show signs of recovery within a week should be replaced with new plants.
5. Give good after care. Water the damaged plants during the growing season giving them at least one inch of water each week.
6. Mulch. Applying two to three inches of mulch around the base of damaged plants may help them survive during the winter.
Symptoms and Diagnosis
On annuals and perennials leaves, stems and flowers may be shredded, torn and knocked off. On trees and shrubs leaves, twigs and branches may be tattered, split and broken. Fruit may be pitted and knocked to the ground. The scars from hail damage to trees occur on the upper side of branches and on the side of the trunk facing the storm. The tree may take a very long time to recover. The damage increases the vulnerability of the tree to decay causing fungi and insect activity.
Integrated Pest Management Strategies
1. Evaluate damage. Assess the damage to the plants and estimate how long they have left to recover from the damage before the onset of winter.
2. Cleanup. Severely damaged trees and shrubs with broken branches should have them removed promptly. Less severe wounds may slowly heal naturally over a period of time. Damaged fruit should be removed. Do not fertilize hail damaged trees.
3. Fertilize. If the damage is early in the growing season, annuals and perennials may benefit from a light application of fertilizer. Immediately remove any damaged leaves from these plants.
4. Replace. Annuals and perennials that do not show signs of recovery within a week should be replaced with new plants.
5. Give good after care. Water the damaged plants during the growing season giving them at least one inch of water each week.
6. Mulch. Applying two to three inches of mulch around the base of damaged plants may help them survive during the winter.
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文章
Dummer. ゛☀
2017年09月16日
Foliar nematodes, Aphelenchoides spp., are considered disease-causing organisms that attack plant parts above the ground in over 200 host plants. They are an emerging problem for gardeners because of this broad host range, ability to spread quickly and lack of symptom recognition. Additionally, there are few products registered for use in the home landscape that can limit their infection and spread. Some of the most common hosts include anemone, strawberry, hosta, phlox, verbena, zinnia, carnation, impatiens, begonia, fern and African violet.
Symptoms and Diagnosis
The two most prominent foliar nematodes are A. ritzemabosi called the chrysanthemum foliar nematode and A. fragariae called the strawberry crimp or fern nematode. Both are serious pathogens of ornamental plants both in the greenhouse and outside in the garden. However, their host ranges rarely overlap except on African violet, begonia, gloxinia, Siberian bugloss, violet and verbena. The most prominent symptoms occur in the leaves of infected plants. Two interveinal symptom types are commonly found. The first is a development of linear lesions between the leaf veins causing the leaf to become striped in appearance. Plants that have parallel venation like hosta are likely to display this leaf pattern. The second leaf symptom which is more common is the development of angular, water-soaked lesions occurring between the veins of netted-veined plants. These lesions will become brown and eventually turn black and perhaps drop out of the leaf leaving a ragged, wind-tattered appearance. Other symptoms may appear as stunting, leaf proliferation or bunching of leaves around the crown, multicolored leaves, lack of flowering and plant death. It is not uncommon to find new leaves emerging without symptoms while older leaves turn brown and collapse or fall. This occurs because the spread of nematodes requires free moisture. Lack of water on the leaves causes them to become localized so that they cannot move to new plant parts. Thus, under dry conditions, new leaves may appear unaffected.
Life Cycle
Unique to this group of pathogens, foliar nematodes live in and feed upon the aerial portion of the plant, mostly leaves, and are rarely associated with the soil unless it is within infested plant debris. A common over wintering site is within the crown of the plant where new leaves will emerge in spring. They commonly spread from plant to plant by splashing water and leaf contact. Nematodes can swim in a thin film of water to move upward towards leaves where they enter stomata. Another way they spread is by vegetative cuttings of leaves, stems and crowns. Gardeners who are active in propagation are likely to move the pathogen with every division. Nematodes remain active, feeding on leaf tissue and repeating their life cycle multiple times in the growing season. Once it becomes cooler, they will migrate towards the plant crown, live in dormant buds or leaf debris.
Integrated Pest Management Strategies
1. Sanitation: remove all infested debris from the plant and ground. This should be buried or burned. Floors and benches of propagation areas should be thoroughly cleaned of debris. Tools and containers should be heat treated in an oven or steamed for 30 minutes at 180 F.
2. Destroy infested plants: it is almost impossible to rid the plant of foliar nematodes. Therefore, it is best to destroy infested plants. Plants that are suspected of being infected should be isolated from healthy plants.
3. Select disease-free plants: Only healthy, nematode-free plants should be purchased and used for propagation stock. Contact between plants and extended periods of free moisture from overhead irrigation should be avoided. Dormant plant material can be treated with warm water (120 F) for 15 minutes to eliminate the nematode infestation on valuable planting stock.
4. Resistance: Some resistant cultivars of chrysanthemum are available. At this time, no resistant varieties are known for other garden plants.
5. Pesticides: Commercial growers who are certified for using nematicides can control foliar nematodes on greenhouse and nursery crops. There are no nematicides labeled for residential users.
Symptoms and Diagnosis
The two most prominent foliar nematodes are A. ritzemabosi called the chrysanthemum foliar nematode and A. fragariae called the strawberry crimp or fern nematode. Both are serious pathogens of ornamental plants both in the greenhouse and outside in the garden. However, their host ranges rarely overlap except on African violet, begonia, gloxinia, Siberian bugloss, violet and verbena. The most prominent symptoms occur in the leaves of infected plants. Two interveinal symptom types are commonly found. The first is a development of linear lesions between the leaf veins causing the leaf to become striped in appearance. Plants that have parallel venation like hosta are likely to display this leaf pattern. The second leaf symptom which is more common is the development of angular, water-soaked lesions occurring between the veins of netted-veined plants. These lesions will become brown and eventually turn black and perhaps drop out of the leaf leaving a ragged, wind-tattered appearance. Other symptoms may appear as stunting, leaf proliferation or bunching of leaves around the crown, multicolored leaves, lack of flowering and plant death. It is not uncommon to find new leaves emerging without symptoms while older leaves turn brown and collapse or fall. This occurs because the spread of nematodes requires free moisture. Lack of water on the leaves causes them to become localized so that they cannot move to new plant parts. Thus, under dry conditions, new leaves may appear unaffected.
Life Cycle
Unique to this group of pathogens, foliar nematodes live in and feed upon the aerial portion of the plant, mostly leaves, and are rarely associated with the soil unless it is within infested plant debris. A common over wintering site is within the crown of the plant where new leaves will emerge in spring. They commonly spread from plant to plant by splashing water and leaf contact. Nematodes can swim in a thin film of water to move upward towards leaves where they enter stomata. Another way they spread is by vegetative cuttings of leaves, stems and crowns. Gardeners who are active in propagation are likely to move the pathogen with every division. Nematodes remain active, feeding on leaf tissue and repeating their life cycle multiple times in the growing season. Once it becomes cooler, they will migrate towards the plant crown, live in dormant buds or leaf debris.
Integrated Pest Management Strategies
1. Sanitation: remove all infested debris from the plant and ground. This should be buried or burned. Floors and benches of propagation areas should be thoroughly cleaned of debris. Tools and containers should be heat treated in an oven or steamed for 30 minutes at 180 F.
2. Destroy infested plants: it is almost impossible to rid the plant of foliar nematodes. Therefore, it is best to destroy infested plants. Plants that are suspected of being infected should be isolated from healthy plants.
3. Select disease-free plants: Only healthy, nematode-free plants should be purchased and used for propagation stock. Contact between plants and extended periods of free moisture from overhead irrigation should be avoided. Dormant plant material can be treated with warm water (120 F) for 15 minutes to eliminate the nematode infestation on valuable planting stock.
4. Resistance: Some resistant cultivars of chrysanthemum are available. At this time, no resistant varieties are known for other garden plants.
5. Pesticides: Commercial growers who are certified for using nematicides can control foliar nematodes on greenhouse and nursery crops. There are no nematicides labeled for residential users.
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文章
Dummer. ゛☀
2017年09月16日
The water needs of different plants vary greatly. Some factors to consider include the species and age of the plant, the type of soil in which it is planted, and its exposure. The symptoms of drought stress may be similar to the symptoms of over watering or even to some pest and disease problems. It is important to identify the causes of the problem in order to take corrective steps.
Symptoms and Diagnosis
With mild water deficiency, plants are usually slow growing and stunted. Some plant leaves turn from shiny to dull at first signs of stress. Grasses, which are the first to show the loss of water in the landscape, will show signs of wilt. Footprints in wilted grass persist instead of disappearing as grass blades spring upright.
Under long term water stress, plants might permanently wilt or stop growing; they may have diminished crops and discolored leaves, flower buds and flowers. Plants may eventually die. Bare spots will appear in ground covers. Water-stressed plantings may show the effects of weeds, insect pests, and diseases.
Drought symptoms can be very confusing, and can vary with different types of plants. Woody plants under drought stress can have many symptoms including yellowing, wilting leaves that develop early fall color and burning or scorching on edges of leaves. Plants may drop some or all of their leaves and appear dead.
Most established woody plants recover when watered. Plants that appear to be dead, having dropped all or most of their leaves, might recover when watered. Scrape the outer layer of a twig or the bark to see if a green layer exists indicating it is still alive. Do not remove this plant the first season. Wait until the following year to see if it recovers.
Integrated Pest Management Strategies
1. Water well. Deep watering encourages roots to go deep down in the soil to where it is moist and a lot cooler. Water less frequently but for longer periods, so water reaches deep into soil. Good thorough watering promotes healthier plants.
2. Investigate using water conserving drip emitters or soaker hoses on a timer. Adjust watering frequency and amounts based on season, temperature and amount of rainfall. Overhead watering uses more water and can promote fungal disease.
3. Add mulch to individual plants or beds. Add organic matter such as compost or rotted manure to plantings ---drought becomes less of a problem as soils with high humus levels hold more moisture. Take care to keep mulch away from stems.
4. Plant selection. Use appropriate plants, which catalogs and plant tags often marked as drought tolerant or resistant. Also consider native plants, which generally adapt better, have lower water demands and fewer pest problems.
5. Water only when necessary, based on condition of the plant. Most plants will normally wilt in hot sun, and then recover when watered. Also, a dry surface is not always a sign of water need. The surface generally dries out first and is not a true indicator of what is going on down deep near the plant root. Make use of a hand trowel or soil probe to check for moisture.
6. Give priority to watering newly planted trees and shrubs during periods of drought. Young plants have not had sufficient time to establish deep root systems, and depend on surface water for survival. Do not let the root balls of newly planted trees and shrubs dry out completely or become too saturated. Before watering use a soil probe or a hand trowel. Inspect plants several times a week during drought conditions.
Symptoms and Diagnosis
With mild water deficiency, plants are usually slow growing and stunted. Some plant leaves turn from shiny to dull at first signs of stress. Grasses, which are the first to show the loss of water in the landscape, will show signs of wilt. Footprints in wilted grass persist instead of disappearing as grass blades spring upright.
Under long term water stress, plants might permanently wilt or stop growing; they may have diminished crops and discolored leaves, flower buds and flowers. Plants may eventually die. Bare spots will appear in ground covers. Water-stressed plantings may show the effects of weeds, insect pests, and diseases.
Drought symptoms can be very confusing, and can vary with different types of plants. Woody plants under drought stress can have many symptoms including yellowing, wilting leaves that develop early fall color and burning or scorching on edges of leaves. Plants may drop some or all of their leaves and appear dead.
Most established woody plants recover when watered. Plants that appear to be dead, having dropped all or most of their leaves, might recover when watered. Scrape the outer layer of a twig or the bark to see if a green layer exists indicating it is still alive. Do not remove this plant the first season. Wait until the following year to see if it recovers.
Integrated Pest Management Strategies
1. Water well. Deep watering encourages roots to go deep down in the soil to where it is moist and a lot cooler. Water less frequently but for longer periods, so water reaches deep into soil. Good thorough watering promotes healthier plants.
2. Investigate using water conserving drip emitters or soaker hoses on a timer. Adjust watering frequency and amounts based on season, temperature and amount of rainfall. Overhead watering uses more water and can promote fungal disease.
3. Add mulch to individual plants or beds. Add organic matter such as compost or rotted manure to plantings ---drought becomes less of a problem as soils with high humus levels hold more moisture. Take care to keep mulch away from stems.
4. Plant selection. Use appropriate plants, which catalogs and plant tags often marked as drought tolerant or resistant. Also consider native plants, which generally adapt better, have lower water demands and fewer pest problems.
5. Water only when necessary, based on condition of the plant. Most plants will normally wilt in hot sun, and then recover when watered. Also, a dry surface is not always a sign of water need. The surface generally dries out first and is not a true indicator of what is going on down deep near the plant root. Make use of a hand trowel or soil probe to check for moisture.
6. Give priority to watering newly planted trees and shrubs during periods of drought. Young plants have not had sufficient time to establish deep root systems, and depend on surface water for survival. Do not let the root balls of newly planted trees and shrubs dry out completely or become too saturated. Before watering use a soil probe or a hand trowel. Inspect plants several times a week during drought conditions.
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文章
Dummer. ゛☀
2017年09月16日
Sclerotia of southern blight (resembling mustard seeds) at the crown of Japanese anemone (Anemone)
Crown rot, sometimes called southern blight or southern stem rot, is caused by several soil-borne fungi. It affects herbaceous plants and some woody plants but is most commonly found on ajuga, anemone, campanula, chrysanthemum, delphinium, hosta, hydrangea, iris, narcissus, phlox, rudbeckia, scabiosa, sedum, and tulip. The problem generally requires removal of the diseased plant.
Symptoms and Diagnosis
Crown rot causes deterioration and rotting of the tissues at the crown of the plant causing the leaves to turn yellow, collapse, and die. When the temperature exceeds 70 degrees F, infected plants develop discolored, water-soaked stem lesions near the soil line. During periods of high humidity, coarse cottony webbing (mycelium) develops and fans out over the stem base and surrounding soil. Sclerotia, which resemble mustard seeds and vary from white to reddish tan to light brown in color, develop at the base of the plant. Enough sclerotia may form to create a crust on the soil.
Life Cycle
The fungi which cause crown rot (Pellicularia rolfsii, Sclerotium delphinii, and Sclerotium rolfsii) survive in the soil and are spread by flowing water, transported or contaminated soil, transplants, and tools. Conditions of 86–95 degrees F for several days with intermittent rains are conducive for fungal development.
Integrated Pest Management Strategies
1. Remove diseased plants as soon as they are noticed. Plants can be buried, but do NOT place them in your compost pile.
2. Excavate surrounding soil. Dig out and replace the soil to a depth of 8 inches and 6 inches beyond the diseased area.
3. Solarize the soil. If you do not remove the soil and the area receives at least two to three hours of direct sun, solarize it. Cover the area with clear plastic and leave it for two to three months in the heat of the summer.
4. Provide better drainage. Increasing the organic content of the soil and improving drainage will make the environment less desirable to the fungus.
5. Sterilize all tools. Clean all tools used in digging with a solution of 1–part bleach to 9–parts water to disinfect the tools and reduce spreading the disease to other locations in your garden.
6. Try fungicides. Pesticides registered for control of crown rot include mancozeb and thiophanate methyl (Cleary 3336).
Crown rot, sometimes called southern blight or southern stem rot, is caused by several soil-borne fungi. It affects herbaceous plants and some woody plants but is most commonly found on ajuga, anemone, campanula, chrysanthemum, delphinium, hosta, hydrangea, iris, narcissus, phlox, rudbeckia, scabiosa, sedum, and tulip. The problem generally requires removal of the diseased plant.
Symptoms and Diagnosis
Crown rot causes deterioration and rotting of the tissues at the crown of the plant causing the leaves to turn yellow, collapse, and die. When the temperature exceeds 70 degrees F, infected plants develop discolored, water-soaked stem lesions near the soil line. During periods of high humidity, coarse cottony webbing (mycelium) develops and fans out over the stem base and surrounding soil. Sclerotia, which resemble mustard seeds and vary from white to reddish tan to light brown in color, develop at the base of the plant. Enough sclerotia may form to create a crust on the soil.
Life Cycle
The fungi which cause crown rot (Pellicularia rolfsii, Sclerotium delphinii, and Sclerotium rolfsii) survive in the soil and are spread by flowing water, transported or contaminated soil, transplants, and tools. Conditions of 86–95 degrees F for several days with intermittent rains are conducive for fungal development.
Integrated Pest Management Strategies
1. Remove diseased plants as soon as they are noticed. Plants can be buried, but do NOT place them in your compost pile.
2. Excavate surrounding soil. Dig out and replace the soil to a depth of 8 inches and 6 inches beyond the diseased area.
3. Solarize the soil. If you do not remove the soil and the area receives at least two to three hours of direct sun, solarize it. Cover the area with clear plastic and leave it for two to three months in the heat of the summer.
4. Provide better drainage. Increasing the organic content of the soil and improving drainage will make the environment less desirable to the fungus.
5. Sterilize all tools. Clean all tools used in digging with a solution of 1–part bleach to 9–parts water to disinfect the tools and reduce spreading the disease to other locations in your garden.
6. Try fungicides. Pesticides registered for control of crown rot include mancozeb and thiophanate methyl (Cleary 3336).
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文章
Dummer. ゛☀
2017年09月16日
Close-up of spots caused by Botrytis blight on Chinese dogwood (Cornus kousa)
Botrytis blight, also know as gray mold, is a fungal disease caused by several species in the genus Botrytis. It affects the buds, flowers, leaves, and bulbs of many plants including: African violet, begonia, chrysanthemum, cyclamen, dahlia, geranium, lily, peony, rose, and tulip. The extent and severity depends on weather conditions and cultural practices. This disease is the primary cause of decay in cut flowers.
Symptoms and Diagnosis
Botrytis blight causes buds and flowers to develop abnormally and turn brown. Flowers may have irregular flecks and brown spots; older flowers tend to rot quickly. Soft, brown spots appear on leaves, stem, and flowers following a cool damp period. Affected parts may be covered with a gray mold following damp, cool weather.
Life Cycle
Botrytis fungi overwinter as sclerotia on dead plant debris in the garden. In the spring, spores form and spread by wind or splashing water to infect dying, wounded, or extremely soft plant tissues. Fungal mycelial strands (web blight) from previously infected plant parts can grow onto healthy plant parts and infect them. The fungus is capable of invading tissue during all periods of the growing season and multiplies rapidly in declining foliage, hence, the need for good sanitation.
Integrated Pest Management Strategies
1. Practice good sanitation. Remove and destroy all infected plant parts as soon as they are observed.
2. Avoid overcrowding. Give adequate space between plants to allow for good air circulation. The fungus thrives in areas that are cool and moist and where plants are overcrowded.
3. Do not overfeed. Avoid fertilizing with excessive amounts of nitrogen. This can cause tender growth that is very susceptible to the fungus. Get a soil test to guide fertilizer practices.
4. Avoid overhead watering. Water on foliage and flowers from overhead irrigation, especially on cool, cloudy days, promotes the disease. Try to keep buds and flowers dry. Water early in the day so the plants have enough time to dry off completely.
5. Use fungicides. Depending upon the susceptibility of the plant to this disease, spray every 10 days with a fungicide. Pesticides registered for use include copper, captan, chlorothalonil (Daconil), mancozeb, maneb, sulfur, and thiophanate methyl (Cleary 3336). Fungicides must be applied in advance of the disease as a protectant.
Botrytis blight, also know as gray mold, is a fungal disease caused by several species in the genus Botrytis. It affects the buds, flowers, leaves, and bulbs of many plants including: African violet, begonia, chrysanthemum, cyclamen, dahlia, geranium, lily, peony, rose, and tulip. The extent and severity depends on weather conditions and cultural practices. This disease is the primary cause of decay in cut flowers.
Symptoms and Diagnosis
Botrytis blight causes buds and flowers to develop abnormally and turn brown. Flowers may have irregular flecks and brown spots; older flowers tend to rot quickly. Soft, brown spots appear on leaves, stem, and flowers following a cool damp period. Affected parts may be covered with a gray mold following damp, cool weather.
Life Cycle
Botrytis fungi overwinter as sclerotia on dead plant debris in the garden. In the spring, spores form and spread by wind or splashing water to infect dying, wounded, or extremely soft plant tissues. Fungal mycelial strands (web blight) from previously infected plant parts can grow onto healthy plant parts and infect them. The fungus is capable of invading tissue during all periods of the growing season and multiplies rapidly in declining foliage, hence, the need for good sanitation.
Integrated Pest Management Strategies
1. Practice good sanitation. Remove and destroy all infected plant parts as soon as they are observed.
2. Avoid overcrowding. Give adequate space between plants to allow for good air circulation. The fungus thrives in areas that are cool and moist and where plants are overcrowded.
3. Do not overfeed. Avoid fertilizing with excessive amounts of nitrogen. This can cause tender growth that is very susceptible to the fungus. Get a soil test to guide fertilizer practices.
4. Avoid overhead watering. Water on foliage and flowers from overhead irrigation, especially on cool, cloudy days, promotes the disease. Try to keep buds and flowers dry. Water early in the day so the plants have enough time to dry off completely.
5. Use fungicides. Depending upon the susceptibility of the plant to this disease, spray every 10 days with a fungicide. Pesticides registered for use include copper, captan, chlorothalonil (Daconil), mancozeb, maneb, sulfur, and thiophanate methyl (Cleary 3336). Fungicides must be applied in advance of the disease as a protectant.
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