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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Brown patch (Rhizoctonia solani) is a fungus which attacks most commonly cultivated grasses: bent grass, perennial ryegrass, tall fescue and annual bluegrass, but especially tall fescue. There are various species of Rhizoctonia which can attack grass plants from seedling stage too mature plants and are pathogenic over a wide range of environmental conditions. It is common in dense, highly fertilized turf.
Brown patch may also be referred to as Rhizoctonia blight. Large brown patch is used to describe the disease in zoysiagrass. Large Patch in Zoysia Lawns Symptoms and Diagnosis Symptoms vary depending on the turfgrass species and mowing height. Susceptibility of the cultivar, management practices and weather conditions determine the degree of injury. More than one fungi may also be present in the lawn. As the name suggests, symptoms include small circular patches of brown, lifeless grass. These patches often enlarge and join together, reaching diameters of six feet or more. Newly established lawns may be more severely damaged than established lawns.
In cool-season grasses water soaked circular patches that range from a few inches to several feet in diameter appear. The affected leaves wilt and turn light brown, but remain upright. A dark, grayish-black ring (smoke ring) of wilted grass often is present around the perimeter of the diseased areas in the early morning. Life Cycle Disease development requires the presence of an active fungus, vigorous growth of a susceptible grass, daytime temperatures ranges between 75 degrees and 85 degrees F, the presence of free moisture on the foliage and night temperatures below 68 degrees F. This fungus feeds on dead organic matter in the soil, but will attack grass when the right environmental conditions arise. Hot, humid conditions promote spread of the fungi.
Integrated Pest Management Strategies 1. Fertilizer. Avoid heavy, early spring and summer fertilization, particularly with soluble nitrogen. Avoid over fertilization of turfgrasses growing in shaded areas. Use slow-release nitrogen fertilizers. Fertilize to maintain adequate but not lush growth during the growing season. Properly fertilized turf will recover quicker from disease injury than will under-fertilized turf. 2. Collect waste. Remove and dispose of clippings from infected areas or when conditions are conducive to disease development. Mulching mowers that chop clippings to 1/4 inch or less do not contribute to brown patch development. Mow only when the grass is dry, being sure to remove no more than one third of the top growth.
3. Prune. Prune trees and shrubs to allow air movement and light penetration to reach the turfgrass. 4. Watering. Water to a depth of about 6 inches no more than once a week. More frequent watering provides an ideal environment for disease development. 5. Drainage. Provide good surface and subsurface water drainage to reduce humidity in the turf canopy.
6. Fungicide. Use a preventive fungicide program with recommended fungicides. Read labels for proper fungicides and their use. 7. Replant dead areas. The disease can occur quickly, spread rapidly and then stop abruptly as environmental conditions change. Frequently, the best and only recourse is to replant dead areas at the proper time of year—early fall or spring.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Anthracnose is usually associated with turf suffering from heat injury in midsummer, but it can also develop in spring and fall. Anthracnose may occur in conjunction with other diseases such as summer patch and Rhizoctonia brown patch. It is a common disease of bentgrass and annual bluegrass.
The most severe damage is when the anthracnose fungus (Colletotrichum) infects and colonizes the lower crown of the turfgrass plant. This is sometimes referred to as basal crown rot. Plants with a crown rot are killed, resulting in a thinning of the turfgrass stand. Spore-producing acervuli and small, black resting structures called sclerotia form on the decaying crown. The scattered structures are visible with a hand lens and appear as small pepper-like dots.
Symptoms and Diagnosis From a distance, affected bentgrass and/or annual bluegrass appear unthrifty and have a yellow or bronze cast. Affected turf may wilt rapidly during midday and require frequent watering . Individual plants affected with anthracnose first turn yellow and then die. Distinct leaf spots are not commonly formed by the anthracnose fungus. Instead, individual leaf blades fade from dark green to light green and then to yellow. There is no distinct region between healthy and diseased tissue as commonly observed with other leaf spotting fungi. The fungus produces conspicuous black fruiting structures called acervuli in the leaves. The acervuli are abundant in dead tissue and may also form in green, apparently healthy leaves. The black hairy or spiny fruiting bodies are easily visible with a 10X hand lens. Spines associated with ascervuli are diagnostic for Colletotrichum fungi .
Life Cycle Anthracnose may develop throughout the growing season, although it is more common in midsummer when cool-season turf is experiencing heat or drought stress. The anthracnose fungus, Colletotrichum graminicolum, overwinters on living plant material. Stressed turfgrass is most susceptible to infection. The fungus penetrates the root, crown and/or leaf tissue during high humidity and wet weather conditions.
Integrated Pest Management Strategies 1. Fertilizer. Get a soil test and correct fertilizer deficiencies, especially phosphorus and potassium. Very light fertilization with a balanced fertilizer during the summer may help the turf withstand stresses and recover quickly. 2. Mowing. Low frequent mowings enhance disease development. Consider raising mowing height to three inches during midsummer. 3. Watering. Use proper watering practices. Water in early morning with approximately 1 inch of water per week or to a depth of 6 inches. Avoid dry spots and frequent, light waterings.
4. Fungicides. Fungicides are continually being developed for use against fungi. Select one for your disease and read the label before applying any fungicide or pesticide. Pesticides registered for use include: azoxystrobin (Heritage), chlorothalonil (Daconil), Neem extract, copper, mancozeb, maneb, thiophanate methyl (Cleary 3336), and triadimefon.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Whiteflies are common on houseplants and in greenhouses. They are piercing-sucking insects found on the underside of leaves. When disturbed on a heavily infested plant, a white cloud of adults will fly into the air. A large infestation can cause plant damage and loss of leaves. In most cases, it is more of a nuisance than a threat to the plant. Since homes and greenhouses are always warm, they can reproduce throughout the year.
When purchasing new plants, always check under the leaves making sure pests are not present. Also, check branching areas for pests. In the home make a habit of checking the underside of leaves when you water. They are easiest to remove at an early stage. In most cases, the pest will not be spotted until there are adults flying around the plant when they are disturbed.
Symptoms and Diagnosis Identification of the whitefly is easy as an apparent white cloud of small snowflakes rises from foliage when disturbed. The adults are about 1/10 to 1/16 inch in length, wedge shaped, and moth-like with white, powdery wings. Symptoms vary—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 that 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, resulting in stunting, poor growth, defoliation, reduced yields, and sometimes death.
Life Cycle Whiteflies are closely related to scales, mealybugs, and aphids. They undergo complete metamorphosis with all life stages present at any time. Eggs are laid on the underside of the leaves. One female can lay about 200 to 400 eggs. They are usually laid in cigar- or circle-shaped clusters of 30 to 40 eggs. The eggs hatch in about a week into nymphs or crawlers. The crawlers wander about the plant and insert their mouth parts to feed on plant sap. When they molt, they lose their antennae and attach themselves to the underside of the leaves where they continue to feed until they pupate. Adults emerge and are about 1/10 to 1/16 inch long and look like a small white moth. The adult has four wings that are covered with a white, powdery, waxy substance. Within a population, all life stages are present, and generations often overlap. The life cycle takes only 18 days.
Integrated Pest Management Strategies 1. Inspection. Inspect all new plants brought indoors for whitefly. Inspect regularly, and remove by hand older leaves that are heavily infested with whiteflies in a non-mobile nymphal stage. Isolate new plants for a few days before placing them among other plants. 2. 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. One trap for every couple plants is recommended.
3. 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.
Some of the over-the-counter chemicals that could be used contain permethrin or pyrethrins. Insecticidal soap, petroleum oil, and insect growth regulators can also be effective. Before using any insecticide for whitefly control, make sure that the target plant is listed on the label and that the chemical is approved for use indoors. Follow label directions carefully.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Thrips are small (1/5th inch), fringe-winged, pale-colored insects. Normally, they are responsible for negligible problems on houseplants, but plants in the Gesneriaceae family (African violet) and Commelinaceae family (Wandering Jew) are prone to attack.
Symptoms and Diagnosis Thrips are rarely seen because of their small size. The insects feed by puncturing the surface of the plant parts with their single large mandible and slurping the plant juices that seep from the wound. Flowers or leaves may develop silvery streaks. Heavily infested leaves appear brownish or silvery, and growing points may become contorted. Some species of thrips leave sooty spots of black fecal matter on the leaves. Thrips also vector plant diseases. Light blue cards coated with a thin film of oil suspended within two feet above indoor plants can be used as indicator traps. Winged adults caught on the card indicate the presence of thrips.
Life Cycle Female thrips lay their eggs in tiny slits cut into the surface of leaves, flowers, and stems. The eggs can be laid any time of year and hatch within a few days in warm, indoor conditions. The young, called nymphs, are cream to pale green and only visible with magnification. They feed for 7–14 days. Fullgrown nymphs, in most species, drop off the plant to the soil where they burrow down and pupate. Winged adults emerge to complete the cycle. Integrated Pest Management Strategies 1. Keep plants moist. Plants that are kept too dry are more likely to be damaged by thrips. To limit damage or reduce future damage after other initial control measures are used, keep plants moist and increase humidity.
2. Insecticidal soap. Insecticidal soaps, which are considered nontoxic to humans and pets, give good control. Be sure that flowers and growing tips are well covered with the spray. Frequent sprays may be needed until the problem is under control. 3. Use superior horticultural oil sprays. Highly refined oils sold as superior or horticultural oils will also control thrips. The oil suffocates the insects. These oils are highly refined and under proper conditions, can be applied to plants in foliage without damage. Follow label directions to avoid damage to some plants that may be sensitive. Superior oils are also considered nontoxic and are less likely to harm beneficial insects. When spraying indoors, protect surfaces that may be damaged by an oil residue.
4. Use chemical insecticides. Many insecticides registered for use indoors are available. Sprays containing pyrethrins, a plant-derived insecticide, are effective and more benign than other chemical pesticides. Follow label directions and, if possible, spray out-of-doors or in a garage, weather permitting. 5. To limit future problems, inspect plants regularly. With regular inspection, pest problems can be caught when just beginning and control is easier. It is also recommended to isolate newly acquired plants for 2–3 weeks to limit introducing pests indoors. Bringing plants indoors in the fall is another way of introducing insects indoors.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Spider mites are spiders, not insects. They have 8 legs; insects have only 6. Regardless, they are a serious pest both indoors and out. Spider mites are very small, only about 1/50 of an inch long, and so are difficult to see. They have piercing-sucking mouth parts for feeding on plant sap. They can multiply rapidly and in large numbers, cause leaves to take on a dusty, dull appearance. Leaves then yellow and drop or turn brown or tan.
Symptoms and Diagnosis Since the mites are so small, the first sign is generally a plant that looks dull or in poor health. Leaves may appear stippled and curled. Fine webbing may also be evident under the leaves or between the leaf and the stem. When a leaf or branch is tapped over a white sheet of paper, small specks that appear as dust or pepper may be seen to move. Life Cycle Spider mites can go from egg to mature adult in less than two weeks. Indoors as well as outdoors, several generations occur each year.
Integrated Pest Management Strategies 1. Remove mites. Dislodge as many mites as possible using a strong stream of water. Done on a regular basis, this can reduce populations dramatically. Wash the plants either outdoors or in the shower. Protect the soil so it is not washed out of the pot by the spray. 2. Use insecticidal soap. Many insecticidal soaps are also effective in controlling mites so check the label. Other soap products may actually be labeled as miticidal sprays. These soaps are specially formulated to kill mites and not damage plants. They can be very 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 mites. The oil suffocates the mites. Unlike dormant oils, these oils are highly refined and under proper conditions, can be applied to plants in foliage without damage. Follow label directions to avoid damage to some plants that may be sensitive. Superior oils are also considered nontoxic and are less harmful to beneficial insects. When spraying indoors, protect surfaces that may be damaged by an oil residue. 4. Use chemical miticides. Many miticides registered for use indoors are available. Follow directions and if possible, spray out-of-doors or in a garage, weather permitting. Check label for control of spider mites.
5. To limit future problems, inspect plants regularly. With regular inspection, pest problems can be caught when just beginning and control is easier. It is also recommended to isolate newly acquired plants for 2–3 weeks to limit introducing pests indoors. Bringing plants indoors in the fall is another way of introducing mites indoors.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Scale insects are small, piercing-sucking insects that often go unnoticed on indoor plants. The adult forms can be attached to leaves, petioles, and stems. They suck plant juices and can cause plants to lose vigor.
Symptoms and Diagnosis Since the insects are often overlooked, the first signs may be yellowing or wilting leaves that may eventually drop. Leaves may also be covered with a clear sticky substance called honeydew. Honeydew is the insects’ excrement consisting of partially digested sap and may coat the floor and other objects beneath the plant as it spatters down from above. A sticky floor beneath a susceptible plant is a telltale sign that infestation is underway. Under humid conditions, a black mold, called sooty mold, may grow on the honeydew making the leaves look dirty. Closer inspection will reveal small cottony or dome-shaped shells attached to stems and leaves. When pried off with a knifepoint, they may be hollow underneath or house adults and/or eggs. Scale can be differentiated from parts of the plant by scraping. If the structure is green when scraped or cannot be pried off, it is more than likely part of the plant.
Life Cycle Scale insects have a simple life cycle of egg, nymph (crawler), and adult. Indoors, eggs can be laid any time under the protective shell. The eggs hatch and the crawlers seek out new feeding sites. This crawler stage is when scale is easiest to control. When the crawlers settle, they insert their mouth parts into the plant and begin feeding on the plant's sap. The protective shell develops soon after feeding begins and the insect loses use of its legs. Indoor scales can go through many generations a year.
Integrated Pest Management Strategies 1. Remove insects by hand. If caught early, scale insects can be rubbed off by hand, with a discarded toothbrush, or with a cotton swab soaked in isopropyl alcohol. Prune out heavily infested portions of the plant. 2. Use insecticidal soap. Monitor plants frequently. When crawlers are noticed, use insecticidal soaps that are formulated to kill insects and not damage plants. Frequent sprays may be needed until the problem is under control.
3. Use superior horticultural oil sprays. Highly refined oils sold as superior or ultra-refined horticultural oils are effective in controlling both adults and scale crawlers. The oil suffocates the insects. Unlike dormant oils, these oils are highly refined and under proper conditions, can be applied to plants in foliage without damage. Follow label directions to avoid damage to certain plants that may be sensitive. Superior oils are also considered nontoxic and are less likely to harm beneficial insects. When spraying indoors, protect surfaces that may be damaged by an oil residue. 4. Use chemical insecticides. Many insecticides registered for use indoors are available. Sprays containing pyrethrins, a plant-derived insecticide, are effective and more benign than other chemical pesticides. Follow label directions and, if possible, spray out-of-doors or in a garage, weather permitting.
5. To limit future problems, inspect plants regularly. With regular inspection, pest problems can be caught when just beginning and control is easier. It is also recommended to isolate newly acquired plants for 2–3 weeks to limit introducing pests indoors. Bringing plants indoors in the fall is another way of introducing insects indoors. Infested houseplants summered outdoors frequently benefit from the many natural enemies of scale. Be sure to check plants thoroughly before bringing them indoors in fall to be sure they are pest-free.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Although most problems associated with cacti and succulents grown as houseplants are bacterial or fungal diseases caused by overwatering, they do get the occasional insect pest. The most common pests are scale, mealy bugs and root mealy bugs. Less common pests include spider mites and fungus gnats. Control of these pests is difficult because they are small and hide in places that make them hard to see, because they have a cottony or hard covering to protect them or because they have developed a resistance to insecticides.
Symptoms and Diagnosis Mealybugs and scale both damage plants by sucking plant juices resulting in plants that are weak with wrinkled, shriveled leaves. Severe infestations may result in the death of the plant. Often the first symptom of a problem is stickiness or black mold on or near the plant. More careful examination will reveal the actual insect. Scale insects resemble small cottony or dome-shaped shells. They are attached to stems and leaves but can be scraped or pried off.
Mealybugs are 1/5 to 1/3 inch long, and have a waxy, white, cottony appearance. They are slow moving and usually are in clusters along leaf veins or spines, on the underside of leaves, and in hidden areas at joints. Root mealy bugs live in the soil and look like white deposits on the roots. In addition to the damage caused by sucking juices from the roots, root mealy bugs make the plant more susceptible to rot from bacterial and fungal infections. Fungus gnats are 1/8 to 1/16-inch long black flies that resemble mosquitoes. They are most often seen hovering above the soil surface. Adult flies do not cause any damage but the larva live in the soil consuming organic matter and roots. Large plants are usually not affected by the root damage but seedlings may be stunted or killed.
Spider mites also damage cacti and succulents by sucking the plant’s juices. The first sign of spider mites is usually webbing and small brown dots, especially on younger growth, where the plant's epidermis has been damaged. Spider mites are very small, only about 1/50 of an inch long, and will look like dust when the affected area is tapped over a piece of paper. Life Cycle Consult the following IPM pages for detailed information on the life cycle of these pests: Mealybugs, Scale, Spider mites and Fungus gnats.
Integrated Pest Management Strategies 1. Practice good cultural techniques. A healthy plant is better able to overcome insect damage. Be sure to grow your cacti and succulents in the conditions recommended for the species including proper sunlight, water and drainage. Practice good hygiene by keeping the pots free of dead leaves and spent flowers. 2. Quarantine new plants. To ensure that you do not introduce pests to your healthy plants, check new plants carefully and quarantine them until you are sure they are pest-free. If you do find pests on new plants, treat the problem immediately or discard the plant.
3. Wash mealybugs and spider mites off the plant with a strong stream of water. Cover the soil in the pot to prevent overwatering or to keep the soil from washing away. Spider mites are most troublesome in spots with low humidity and poor ventilation. Root mealy bugs may also be washed away if they are noticed on the roots when repotting the plant. 4. Remove mealybugs and scale using cotton swabs dipped in alcohol. Spraying the plant with a dilute alcohol solution (1:3) may help control pests that are not easily visible but the solution may damage the epidermis of sensitive cacti and succulents. Test a small area before spraying the entire plant. 5. Use yellow sticky traps to control adult fungus gnats.
6. Use insecticidal soap but be aware that it may damage some plants. Cacti have oils and waxes that may make them susceptible to damage from the soap. Be sure to read the product’s label to see if it is safe for your plant. It is a good idea to test a small area of the plant before spraying the entire plant. 7. Use insecticides such as Neem or pyrethrins. Always check the label to be sure it is safe for your plant. 8. Use a systemic insecticide such as imidacloprid or acephate to control pests that are not easily accessible to sprays. Be sure to read the product’s label to see if it is safe for your plant.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Mealybugs are common pests of indoor plants. They can also be serious pests of outdoor plants in warmer climates, such as Florida and California.
Symptoms and Diagnosis Adult females are oval, 1/5 to 1/3 inch long, and have a waxy, white, cottony appearance. They are slow moving and usually are in clusters along leaf veins, on the underside of leaves, and in hidden areas at joints. They are piercing-sucking insects, which feed on plant sap. The insects exude a honeydew, which can cause leaves to become sticky. Ants may be attracted to the sweet liquid. In time, a black mold, called sooty mold, can grow on the honeydew giving the leaves a dirty, sooty appearance. Plants infested with mealybugs become weak, may wilt and turn yellow, and eventually die.
Life Cycle Indoors, eggs can be laid any time of year. Eggs hatch in about 2 weeks. The young mature in 6–8 weeks. Several generations can occur in the same year. Integrated Pest Management Strategies 1. Remove insects. Dislodge as many insects as possible using a strong stream of water. A cotton swab soaked in rubbing alcohol will also effectively remove a few insects. 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 oil sprays. Highly refined oils sold as superior or horticultural oils are also very effective in controlling mealybugs. The oil suffocates the insects. Unlike dormant oils, these oils are highly refined and under proper conditions, can be applied to plants in foliage without damage. Follow label directions to avoid damage to some plants that may be sensitive. Superior oils are also considered nontoxic and are less likely to harm beneficial insects. When spraying indoors, protect surfaces that may be damaged by an oil residue. 4. Use chemical insecticides. Many insecticides registered for use indoors are available. Follow directions and, if possible, spray out-of-doors or in a garage, weather permitting.
5. To limit future problems, inspect plants regularly. With regular inspection, pest problems can be caught when just beginning and control is easier. It is also recommended to isolate newly acquired plants for 2–3 weeks to limit introducing pests indoors. Bringing plants indoors in the fall is another way of introducing insects indoors.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Powdery mildew is a common fungal disease of indoor plants. African violets, begonias, ivy, jade, kalanchoe, poinsettia and rosemary are susceptible to powdery mildew. It thrives best in cool, damp conditions.
Symptoms and Diagnosis Powdery mildew starts as a dusty, white to gray, thread-like coating over leaf surfaces, stems, buds or flowers. It can be partially removed by rubbing the leaves but this will not eliminate the fungus. Life Cycle Powdery mildew is caused by many species of fungi each responsible for causing the disease on a limited number of plant species. That is, the species of fungi that causes powdery mildew on African violets is not the same species that causes powder mildew on rosemary. Therefore, powdery mildew on one plant may not spread to a dissimilar plant. Even given this, both plants may develop powdery mildew from different species of fungi if favorable conditions exist for disease development. Several species of powdery mildew can be common both indoors and out.
Powdery mildew starts as discrete, circular powdery white spots on leaves. It may also be on other above ground plant parts. The fungal mycelium grows and in time can cover large parts of the plant giving them a dusty, powdery, or silvery appearance. Powdery spores are produced that spread to other parts of the plant or related plants. The disease can develop and spread anytime the conditions for growth are favorable. Photosynthesis is impaired and growth may be stunted. Buds fail to mature. The plant declines in growth and vigor and eventually becomes unsightly.
Integrated Pest Management 1. Don’t ask for a problem. Choose healthy plants and purchase mildew resistant cultivars if possible. 2. Sanitation. At the first sign of infection, isolate the plant. Remove and dispose of all infected plant parts. Discard severely infected plants. 3. Evaluate and modify the growth environment. Keep plants in a well-ventilated area and do not overcrowd. Improve air circulation around plants. Avoid wetting leaves when watering, do not water from above.
4. Don’t over fertilize. Avoid high nitrogen fertilizers since powdery mildew attacks new succulent growth. 5. Treat with baking soda. Some gardeners recommend applying a baking soda solution to prevent the fungi from establishing. This changes the pH of the leaf surface. Test on a few leaves first as this may damage some plants. Some may feel this treatment may look as unsightly as the mildew disease itself. 6. Use a commercial fungicide. Valuable plants or crops may require the application of an appropriate fungicide labeled for indoor use, preferably one that is systemic. Be sure to read the label and follow directions.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Oedema is a physiological disorder that develops when roots take up water faster than it can be used by the plant or transpired through the leaves. Water pressure builds up in the internal cells of the leaves causing them to burst, leaving dead cells that are visible as a blister, primarily on the undersides of leaves. Oedema may also be spelled edema.
Geraniums, rhododendrons, begonias, peperomias, jade plants, ficus, schefflera, and camellias are particularily sensitive to conditions that lead to the development of oedema, although almost any broadleaf plant may be affected. Symptoms and Diagnosis These blisters eventually erupt and form white, tan, or brown wart-like corky growths. As the condition worsens, leaves may turn yellow, droop, and fall off. In severely affected plants, blisters also form on the petioles and stems, although this is more rare. The upper surfaces of these leaves will often have indentations above the engorged cells on the undersides. If the problem is not corrected, the plants will become spindly.
On indoor plants, oedema is most prevalent in the late winter, especially during extended periods of cloudy weather. It is likely to develop when the soil is warm and the air is cool and moist. This environment results in rapid water absorption from the soil and slow water loss from the leaves. These conditions are most frequently encountered in greenhouses or indoor situations rather than outdoors but oedema can also be common on container-grown plants.
Integrated Pest Management Strategies 1. Culture. Oedema is a cultural problem so cut back on watering, but avoid letting plants dry out completely. If necessary, move the plant to a larger pot if it dries out too quickly. 2. Greenhouse conditions. When symptoms occur in a greenhouse, promote conditions that allow water loss to balance with water uptake by the roots. Decreasing humidity forces higher transpiration; ventilation is important as well as air temperature.
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