动态第746页 - 绿手指 - 养花技巧、花生病了怎么办、花园打理和设计

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.[图片]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.[图片]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.[图片]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.[图片]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.[图片]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.[图片]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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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.[图片]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.[图片]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.[图片]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.[图片]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.[图片]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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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.[图片]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.[图片]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[图片]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.[图片]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.[图片]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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2017年09月16日

Caterpillars are the larvae of moths and butterflies, and like their winged metamorphoses, they come in all shapes and sizes. While all species share a common appetite for plant foliage, the good news is that the methods for controlling them are basically the same. Before deciding upon a control method, take the time to identify which caterpillars might eventually become the gorgeous butterflies and lovely nocturnal moths we usually welcome to our gardens. These larvae should be protected, and fortunately, most are colorful and harmless.[图片]Caterpillars inflict damage by eating the foliage and stems of just about any plant in your flower or vegetable garden, as well as your fruit and shade trees. Furthermore, they are voracious eaters, and can defoliate a plant in a short period of time. Telltale symptoms of a caterpillar infestation are holes in leaves and chewed leaf edges, as well as leaves that are rolled up or fastened with silk. If you are able to catch the infestation early on, the best strategy for controlling caterpillars is to handpick them, then crush them or drop them in a pail of soapy water. Make sure you also remove rolled or folded leaves that shelter the caterpillars. (Make sure you wear gloves before handling saddleback caterpillars, as their sting is severe.) To prevent inadvertently killing desirable butterflies- and moths-to-be, use a good field guide such as Peterson First Guide to Caterpillars and pick only those caterpillars which become drab adults.[图片]Cleanup and disposal of garden debris throughout the growing season, followed by a thorough end-of-season cleanup, will help reduce the size of future generations of caterpillars. Furthermore, many insects--such as fireflies, ground beetles, soldier beetles, stink bugs, and tachinid flies-- prey upon or parasitize caterpillars, and will gladly assist you in your quest to keep caterpillar numbers under control. Specific recommendations for flowers. An effective but less selective control for caterpillars is to dust or spray all parts of the leaves on which they are feeding (especially the undersides) with BT (Bacillus thuringiensis). Apply at 3-5 day intervals, reapplying after rain, until caterpillars cease to be a problem. For an infestation that is out of control, spray all sides of the leaves with pyrethrum; usually two applications spaced 3-4 days apart will solve the problem.[图片]Specific recommendations for vegetables. There are some species of caterpillars that are particularly troublesome in the vegetable garden. Cabbage loopers, as their name suggests, are very fond of cabbage (including the Chinese variety), and will also feed on lima and snap beans, broccoli, brussel sprouts, cauliflower, lettuce, parsley, radishes, rutabagas and turnips. They damage crops by chewing small to large ragged holes in the foliage, and by boring into developing heads of cabbage family crops. The best control strategy is to spray plants with BT (Bacillus thuringiensis) every 2 weeks until pests are under control, or until heads begin to form in the case of cabbage family members. Other effective controls are handpicking; spraying plants with liquefied and strained cabbage loopers, or hot pepper spray; and planting trap crops such as celery or amaranth. For serious infestations, spray leaves with pyrethrum.[图片]Another caterpillar that shares the cabbage looper's taste in plants is the imported cabbage worm. Symptoms of infestation include ragged holes in the leaves and bits of green excrement; you will also notice white butterflies skipping about from plant to plant. Like cabbage loopers, imported cabbage worms eventually bore into the developing heads of cabbage family plants, turning them into mush in the process. The most effective strategy for controlling this pest is to use an agricultural fleece or net barrier and a preventive BT (Bacillus thuringiensis) spray early in the season, then to use more BT for later infestations. A thorough fall cleanup is essential to prevent recurring infestations, since these pests overwinter in the soil or on garden litter. After harvesting crops, promptly remove all old plants and overgrown weeds, leaving the soil completely bare, then cultivate soil to a depth of 6-8 inches. Make sure old plants are actively composted or destroyed.[图片]European corn borers are most notorious for boring holes into the stalks and ears of the corn plant, but also damage chard, peppers, potatoes and tomatoes. Squash vine borers affect crops such as cucumbers, muskmelons, pumpkins, squash (summer and winter), and watermelons by burrowing into their vines and causing them to wilt. For more information on these pests, see Caterpillars - Borers and Miners: Specific recommendations for vegetables. Parsleyworms are 2 inches long, and are a brightly colored green with yellow-dotted black bands across each body segment. They give off an odor and project orange horns when they are upset. They will someday become lovely, black swallowtail butterflies, so carefully weigh their aesthetic value against the damage inflicted on your carrots, celery, dill, fennel, parsley and parsnip plants before deciding to destroy them. If you decide the parsleyworms are eating excessively into your harvest, reduce their numbers by handpicking them, or try attracting birds such as northern orioles, barn swallows, bluebirds, chickadees, flycatchers and kinglets into your garden.[图片]The tomato hornworm is a large (3 to 5 inches long), green caterpillar with a horn projecting from its rear; it will eventually become a moth whose diurnal feeding habits and ability to hover have earned it the name of "hummingbird moth." The hornworm chews holes in the leaves of dill, eggplant, pepper, potato and tomato plants, and will sometimes also damage the fruits of the latter three. Check damaged plants for dark colored droppings, and spray them with water; this should cause the hornworms to thrash about and enable you to handpick them more easily. If you notice papery cocoons on their backs, remove but don't destroy the caterpillars: they are already doomed by natural parasites, which should be allowed to reproduce. You can also control hornworms with a Bacillus thuringiensis (BT) spray, or a pyrethrum spray if the infestation gets out of hand.[图片]Specific recommendations for trees. This section will address three pests that primarily affect trees: codling moths, gypsy moths, and tent caterpillars. The larvae of codling moths primarily damage apple, apricot and pear crops, both when they are immature and again when they have ripened. Symptoms of infestation include holes in the fruit skin, tunnels through the fruit, and fecal waste in the core; check also for mounds of excrement around the tunnel entrances and for cocoons in the bark crevices. To control this pest, use a preventive spray of Bacillus thuringiensis (BT) early in the season and light horticultural oil later in the season to get the newly hatched larvae before they bore into the fruit. In addition, set out sticky traps to snare the moths during their emergence times (check with orchard growers in your area).[图片]Gypsy moths are imported pests that primarily affect the eastern United States, and their populations fluctuate between sheer nuisance to plague proportions. Their larvae damage host trees by devouring their leaves, often leaving them (and sometimes entire forests) completely defoliated. When the larvae are young, they chew only around leaf edges; by the time they are an inch long, large holes begin to appear in leaves. In July, the mature caterpillars encase themselves in brown shells to pupate. To control this voracious pest, particularly when its population is waxing, spray trees with Bacillus thuringiensis (BT) every 10 to 14 days from late April to mid-June. In June, wrap trunks of vulnerable trees with a piece of burlap a foot wide, hung about chest high; tie it at the center with heavy twine, letting the top fold over to form a skirt. When caterpillars descend from the tree each morning, they will hide under the fold. In the late afternoon, put on garden gloves and sweep the caterpillars off into a container of detergent and water. To prevent future gypsy moth problems, check for egg clusters on lawn furniture before putting it away in the fall, and stone walls, woodpiles, fences, garages and outbuildings throughout the winter. Destroy egg masses by scraping them into a can of kerosene, gasoline or water, or by burning them. Reduce debris on the ground that can serve as protection for egg masses, larvae and pupae.[图片]Tent caterpillars form large, tent-like, silken nests in the forks of tree branches, and can defoliate their woody hosts if given the chance. Remove the nests and destroy the caterpillars by hand. Spray the tree with Bacillus thuringiensis (BT) as soon as you see the nests begin to reappear, and repeat every 5 to 7 days until the pest is gone.

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2017年09月16日

Aphids are a very large and diverse group of insects that plague the garden especially during the beginning and end of the growing season. At least 4,000 aphid species have been identified; variations in color, size, and appearance make it impossible to generalize.[图片]Symptoms and Diagnosis Aphid damage may appear as pale yellow spots on leaves, leaves that are curled, puckered, or stunted, and/or distorted blossoms. Look for aphids at the beginning of the growing season. They should be especially abundant on stems and buds where nitrogen concentrations are higher. Aphids multiply more rapidly with high nitrogen levels. Another sign to look for is a sooty black layer on the leaves. Because aphids suck more plant sap than they can use, they exude honeydew onto leaf surfaces. Envied by honeybees and ants, this honeydew substance is very sweet and molds quickly.[图片]Life Cycle Females lay eggs toward the end of the growing season in the bark or bud scales of their favorite plant. When the eggs hatch the following spring, the nymphs are all female and are called "stem mothers". These females will give live birth to daughters without mating. Toward the end of the growing season, males are produced, mating occurs, and the eggs will again overwinter in the plant material.[图片]Integrated Pest Management Strategies 1. Through good horticultural practices, aphids can be minimized. One step is to control the amount of nitrogen added to the garden. By using slowrelease fertilizers such as ammonium or urea-based fertilizers, compost, decomposed manure, fish emulsion, or liquid seaweed, you slow the rate at which the aphids can reproduce. Another step is to prune moderately in winter and early spring, saving the heavy pruning for midgrowing season. This prevents the aphids from destroying fresh growth in early spring. The last step is to encourage a continuum of flowers that will attract the aphids’ natural predators— ladybugs and praying mantis.[图片]2. Try spraying the aphids off the plants with plain water, or remove them by hand with a cloth. 3. Insecticidal soap can be used, but in moderation, as it will kill beneficial insects as well as the aphids. 4. Insecticidal baits that contain boric acid can be used to control the ants, which have a symbiotic relationship with the aphids. The ants protect the aphids and get the honeydew that they ooze in return. Use caution; boric acid is toxic to people and animals. Ant barriers placed at the base of infested plants is another way to discourage ants and allow predators to attack the aphid population.[图片]5. Silica Aerogel/Pyrethrin is a product that will dissolve the cuticle layer on the insect causing it to dehydrate and die. 6. Use chemical insecticides. Pesticides registered for use include carbaryl (Sevin), disulfoton (Disyston), malathion, bifenthrin, imidacloprid, permethrin, petroleum oil, and pyrethrins.

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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.[图片]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.[图片]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.[图片]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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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.[图片]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.[图片]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.[图片]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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2017年09月16日

Leaf blight, Volutella pachysandrae, on Japanese pachysandra can be very detrimental to the plant. Two other leaf spots, Phyllosticta and Gloeosporium, cause leaf spots on foliage but are not as destructive as Volutella.[图片]Ground covers, such as pachysandra, are sometimes used where grass or other plants will not grow due to low light. Consequently, the environmental stress factors, including prolonged leaf wetness or dry soils, can favor certain infectious diseases in the sites. Symptoms and Diagnosis Volutella blight begins as small, brown to tan spots on the leaves that enlarge to form blotches. These blotches can then spread and coalesce to form a blight where young growing tissue, especially leaves and twigs, are killed. Concentric line patterns form within the brown spots as leaves yellow and fall. Infected stems become brown to black in color and die.[图片]Circular, spreading areas on diseased plants will be noticeable in the planting. The disease will be especially severe when plants are crowded and wet conditions prevail. Life Cycle Many spore masses cause the spread of the disease, which is especially rapid among plants that have been weakened by the attack of scale insects or by winter injury. The sexual stage of this fungus is Pseudonectria pachysandricola. Under moist conditions, salmon- to pink-colored masses of fungal spores form on the surface of dead stems in spring. Initial infections may lead to large patches of plants killed.[图片]Integrated Pest Management Strategies 1. Maintain plant vigor. Purchase healthy plants and maintain this condition by watering during drought. Water early in the day so that drying occurs before evening. Avoid splashing of water. Fertilize as needed or as indicated by soil testing. 2. Select planting area carefully. Plants should be planted in a well-draining soil. If the site is persistently wet, amend the soil or raise the bed before planting. 3. Removal. Lift out and destroy severely diseased plants. Bury or remove from the site. Do not place in the compost pile.[图片]4. Use fungicides. It is difficult to thoroughly apply fungicides unless using a forceful sprayer. Fungicides can be applied beginning in spring and at 7 to 14 day intervals through early summer. Once temperatures rise above 90 degrees F, discontinue application. Pesticides registered for use include chlorothalonil (Daconil), copper, mancozeb, maneb, and thiophanate methyl (Cleary 3336). 5. Mulch. Mulch with leaf mold in the spring to cover up fallen debris containing inoculum. 6. Thinning. Thin plants in fall, during dry weather, to remove dense growth.[图片]7. Pests. Scale is a harmful pest on pachysandra and may make it more susceptible to disease. The female insects are dark brown and shaped like oyster shells. The males are smaller and narrower, pure white, and are very prominent on the leaves and stems. Heavy infestations of scale can be brought under control by applying summer oil spray before the new growth starts in spring. Follow this with several applications of a scale insecticide like malathion or Sevin at 2-week intervals or several applications of a scale insecticide or summer oil every 10 days to 2 weeks starting in mid-May.

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2017年09月16日

Vinca stem canker, Phoma exigua, is a fungal disease that is almost always prevalent during very rainy seasons. This fungal disease of periwinkle or ground myrtle causes shoot tips to become dark brown changing to nearly black as the disease progresses. Stem canker (blight) may be so severe that attempts to maintain vinca plantings fail, and the plants have to be removed and replaced with other non-susceptible ground covers. Damage is most prevalent in cool wet weather in spring and in autumn when soil moisture is high. Newly planted beds, where plantings are thin and not well established, are very susceptible.[图片]Incidence of the disease tapers off during the hot dry weather of summer; however, in prolonged periods of cool wet weather, new infections can occur. Stem canker can also be a severe problem in nurseries where plants are grown under mist propagation. The fungus grows and persists indefinitely in moist soil and plant debris. It is not unusual for new plants to appear healthy when purchased only to become diseased when planted. The causal fungus survives in infested plant debris which is difficult to remove.[图片]Symptoms and Diagnosis Soon after new green shoots appear in spring, vinca stem canker, Phoma exigua, causes shoot tips to become dark brown, wilt, and die back to the soil surface. Some affected stems are nearly black. After several weeks, entire clumps of plants may wither and die. Small, black, dot-like, fruiting bodies develop on the surface of the diseased stem tissue. Life Cycle The sexual stage of this fungus is known as Diaporthe vincae. The spores are produced during very rainy seasons. The fungus grows saprophytically throughout moist soil and commonly colonizes dead and dying plant material. The fungus is believed to overwinter as dormant mycelium and as specksized, brown to black fruiting bodies (pycnidia) on the dead stems and leaves.[图片]The cycle of infection, disease development, symptom expression, and re-infection may be repeated as long as cool, damp conditions prevail and the soil moisture remains high. Integrated Pest Management Strategies 1. Removal of debris. Remove infected plants and prune out diseased parts of the plant in the fall and spring. Discard this material but do not compost. Thin planting in the fall during dry weather to remove dense growth.[图片]2. Purchase disease-free plants. For new beds, select and plant only vigorous, disease-free stock purchased from a reputable nursery. 3. Water. After transplanting, apply only enough water to maintain vigor. Avoid frequent watering if the soil is sufficiently moist for good growth. 4. Fungicides. Under conditions in the spring of extensive and frequent rainfall, fungicides can be applied to diseases beds every 7–10 days. Application should cover all leaves and stems to runoff. Thorough coverage is essential to be effective.

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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.[图片]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.[图片]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.[图片]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.[图片]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.[图片]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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😀 😁 😂 😄 😆 😉 😊 😋 😎 😍 😘 🙂 😐 😏 😣 😯 😪 😫 😌 😜 😒 😔 😖 😤 😭 😱 😳 😵 😠

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