文章
Dummer. ゛☀
2017年09月17日
Cane blight of raspberries is a late season disease caused by the fungus, Leptosphaeria conithyrium. Infected canes may blossom normally, but they usually wilt and die before they can set fruit or while they are heavy with fruit. Black raspberries are more susceptible than red or purple raspberries. Cankers on apples and roses are also caused by this fungus.
Symptoms and Diagnosis
Brown-purple areas develop around cuts or wounds in infected canes. The discoloration will slowly spread down the cane, encircling the stem. Small, smutty patches of olive-green fungal conidia (spores or conidiospores) develop on the bark. The spread of the disease through the canes blocks water movement through the plant, causing wilting and, eventually, death. Cane blight reduces yields because symptoms appear later in the growing season, when branches may be laden with fruit.
Life Cycle
Spores of the fungus overwinter on dead infected canes. In the late spring, fungal spores are spread from plant to plant by the wind and splashing water. Infection takes place when there is sufficient moisture allowing the spores to enter the plant through wounds. Spores may continue to live on dead, infected canes for 2 or more years.
Integrated Pest Management Strategies
1. Prune and destroy all infected stalks. Blighted canes cannot be cured.
2. Do any pruning work during dry weather to allow wounds to dry out and prevent infection by the fungal spores.
3. Prevent damage and wounds to canes by controlling cane borers. Vigorous, adequately fertilized and watered plants are more resistant to injury and less likely to attract harmful insects. If borers have infected canes, the tips will begin to wilt; prune these tips well below any insect punctures.
4. Plant resistant varieties. Red-fruited or purple varieties of raspberry are less susceptible to cane blight.
5. Use fungicides. Pesticides registered for use include copper and mancozeb.
Symptoms and Diagnosis
Brown-purple areas develop around cuts or wounds in infected canes. The discoloration will slowly spread down the cane, encircling the stem. Small, smutty patches of olive-green fungal conidia (spores or conidiospores) develop on the bark. The spread of the disease through the canes blocks water movement through the plant, causing wilting and, eventually, death. Cane blight reduces yields because symptoms appear later in the growing season, when branches may be laden with fruit.
Life Cycle
Spores of the fungus overwinter on dead infected canes. In the late spring, fungal spores are spread from plant to plant by the wind and splashing water. Infection takes place when there is sufficient moisture allowing the spores to enter the plant through wounds. Spores may continue to live on dead, infected canes for 2 or more years.
Integrated Pest Management Strategies
1. Prune and destroy all infected stalks. Blighted canes cannot be cured.
2. Do any pruning work during dry weather to allow wounds to dry out and prevent infection by the fungal spores.
3. Prevent damage and wounds to canes by controlling cane borers. Vigorous, adequately fertilized and watered plants are more resistant to injury and less likely to attract harmful insects. If borers have infected canes, the tips will begin to wilt; prune these tips well below any insect punctures.
4. Plant resistant varieties. Red-fruited or purple varieties of raspberry are less susceptible to cane blight.
5. Use fungicides. Pesticides registered for use include copper and mancozeb.
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文章
Dummer. ゛☀
2017年09月17日
Black rot, caused by the fungus Guignardia bidwellii, is a serious disease of cultivated and wild grapes. The disease is most destructive in warm, wet seasons. It attacks all green parts of the vine – leaves, shoots, leaf and fruit stems, tendrils, and fruit. The most damaging effect is to the fruit. Note: Guignardia bidwellii forma parthenocissi causes a leaf spot on Boston ivy and Virginia creeper. Control is as for black rot of grapes.
Warm, muggy weather in the spring and summer, along with unsprayed fruit of susceptible varieties, may cause fruit to become almost completely rotted by harvest time. Black rot is not difficult to control if good cultural practices are followed along with the use of protective fungicide sprays.
Symptoms and Diagnosis
Leaves: Reddish brown and circular to angular spots appear on the upper surface of the leaves starting in late spring. As spots merge, they form irregular, reddish brown blotches. The number of spots or lesions per leaf varies from 2 to more than 100 depending on the severity of the disease. The center of the leaf spot turns tannish brown and is surrounded by a black margin. Black, speck-sized fruiting bodies (pycnidia) are arranged in a definite ring just inside the margin of the lesion. Only young, rapidly growing leaves are affected.
Fruit: Shortly after the flower petals fall, fruit infection can occur. Most infections start when the fruit is half to almost full size. A small spot will appear that becomes circular and whitish tan, often surrounded by a brown ring. This happens while the berry is still green. The spots grow rapidly and may cover half of the berry within 48 hours. Within a few days the entire berry becomes coal black, hard, and mummified. The surface of the withered fruit is soon covered with minute, black, pimple-like, sporeproducing pycnidia that are arranged in circular zones.
Life Cycle
The black rot fungus overwinters in canes, tendrils, and leaves on the grape vine and on the ground. Mummified berries on the ground or those that are still clinging to the vines become the major infection source the following spring. During rain, microscopic spores (ascospores) are shot out of numerous, black fruiting bodies (perithecia) and are carried by air currents to young, expanding leaves. In the presence of moisture, these spores germinate in 36 to 48 hours and eventually penetrate the leaves and fruit stems. The infection becomes visible after 8 to 25 days. When the weather is wet, spores can be released the entire spring and summer providing continuous infection. Cool weather slows growth of the fungus. It requires warm weather for optimal growth and a period of 2 to 3 days of rain, drizzle, or fog.
New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather. During August, the pycnidia are transformed into the overwintering stage (pycnosclerotia) that gives rise to perithecia within which the spring ascospores are produced, completing the disease cycle.
Integrated Pest Management Strategies
1. Planting. Space vines properly and choose a planting site where the vines will be exposed to full sun and good air circulation. Keep the vines off the ground and insure they are properly tied, limiting the amount of time the vines remain wet thus reducing infection.
2. Sanitation. Keep the fruit planting and surrounding areas free of weeds and tall grass. This practice will promote lower relative humidity and rapid drying of vines and thereby limit fungal infection.
3. Pruning. Prune the vines in early winter during dormancy. Select only a few strong, healthy canes from the previous year’s growth to produce the following season’s crop. Remove these prunings from the vineyard and burn or destroy.
4. Cultivation. Cultivate the vineyard before budbreak to bury the mummified berries. Diseased berries covered with soil do not produce spores that will reach the developing vines. For homegrown grapes, use 2–3 inches of leaf mulch or fine bark to cover infected debris.
5. Fungicides. Use protective fungicide sprays. Pesticides registered to protect the developing new growth include copper, captan, ferbam, mancozeb, maneb, triadimefon, and ziram. Important spraying times are as new shoots are 2 to 4 inches long, and again when they are 10 to 15 inches long, just before bloom, just after bloom, and when the fruit has set.
6. Cultivars. Cultivars with large, juicy berries are the most susceptible. In general, grapes that ripen late in the season are affected the least. Most commercial cultivars are sufficiently resistant if adequately protected with a fungicide spray program.
Warm, muggy weather in the spring and summer, along with unsprayed fruit of susceptible varieties, may cause fruit to become almost completely rotted by harvest time. Black rot is not difficult to control if good cultural practices are followed along with the use of protective fungicide sprays.
Symptoms and Diagnosis
Leaves: Reddish brown and circular to angular spots appear on the upper surface of the leaves starting in late spring. As spots merge, they form irregular, reddish brown blotches. The number of spots or lesions per leaf varies from 2 to more than 100 depending on the severity of the disease. The center of the leaf spot turns tannish brown and is surrounded by a black margin. Black, speck-sized fruiting bodies (pycnidia) are arranged in a definite ring just inside the margin of the lesion. Only young, rapidly growing leaves are affected.
Fruit: Shortly after the flower petals fall, fruit infection can occur. Most infections start when the fruit is half to almost full size. A small spot will appear that becomes circular and whitish tan, often surrounded by a brown ring. This happens while the berry is still green. The spots grow rapidly and may cover half of the berry within 48 hours. Within a few days the entire berry becomes coal black, hard, and mummified. The surface of the withered fruit is soon covered with minute, black, pimple-like, sporeproducing pycnidia that are arranged in circular zones.
Life Cycle
The black rot fungus overwinters in canes, tendrils, and leaves on the grape vine and on the ground. Mummified berries on the ground or those that are still clinging to the vines become the major infection source the following spring. During rain, microscopic spores (ascospores) are shot out of numerous, black fruiting bodies (perithecia) and are carried by air currents to young, expanding leaves. In the presence of moisture, these spores germinate in 36 to 48 hours and eventually penetrate the leaves and fruit stems. The infection becomes visible after 8 to 25 days. When the weather is wet, spores can be released the entire spring and summer providing continuous infection. Cool weather slows growth of the fungus. It requires warm weather for optimal growth and a period of 2 to 3 days of rain, drizzle, or fog.
New black rot infections continue into late spring and summer during prolonged periods of warm, rainy weather. During August, the pycnidia are transformed into the overwintering stage (pycnosclerotia) that gives rise to perithecia within which the spring ascospores are produced, completing the disease cycle.
Integrated Pest Management Strategies
1. Planting. Space vines properly and choose a planting site where the vines will be exposed to full sun and good air circulation. Keep the vines off the ground and insure they are properly tied, limiting the amount of time the vines remain wet thus reducing infection.
2. Sanitation. Keep the fruit planting and surrounding areas free of weeds and tall grass. This practice will promote lower relative humidity and rapid drying of vines and thereby limit fungal infection.
3. Pruning. Prune the vines in early winter during dormancy. Select only a few strong, healthy canes from the previous year’s growth to produce the following season’s crop. Remove these prunings from the vineyard and burn or destroy.
4. Cultivation. Cultivate the vineyard before budbreak to bury the mummified berries. Diseased berries covered with soil do not produce spores that will reach the developing vines. For homegrown grapes, use 2–3 inches of leaf mulch or fine bark to cover infected debris.
5. Fungicides. Use protective fungicide sprays. Pesticides registered to protect the developing new growth include copper, captan, ferbam, mancozeb, maneb, triadimefon, and ziram. Important spraying times are as new shoots are 2 to 4 inches long, and again when they are 10 to 15 inches long, just before bloom, just after bloom, and when the fruit has set.
6. Cultivars. Cultivars with large, juicy berries are the most susceptible. In general, grapes that ripen late in the season are affected the least. Most commercial cultivars are sufficiently resistant if adequately protected with a fungicide spray program.
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文章
Dummer. ゛☀
2017年09月17日
Black knot is a name used to describe a disease of woody stems with black, knotty, outgrowths. It is most widespread on plum and cherry trees, but also infects apricots and peaches. Infection occurs in the spring, but symptoms of the disease may not be obvious until the following spring or even in later seasons.
Symptoms and Diagnosis
Initially the bark of infected twigs and medium-sized branches will begin to crack in the springtime. A light yellow discoloration and cork-like swelling occurs on infected areas. Knotted areas later turn an olive-green color and finally turn black and harden during the summer. The swelling weakens branches and may stunt or kill smaller branches due to decreased water and nutrient flow.
Life Cycle
Dibotryon morbosum is the fungus responsible for causing black knot disease on cherries and plums. Spores overwinter in the blackened "knots" of infected branches. Disease spores are spread to new hosts by wind during warm spring weather when temperatures are between 55–75 degrees F and there is rain or high humidity. Trees are weakened because the knots disrupt the normal flow of water and nutrients throughout the branches. Twig dieback is common.
Integrated Pest Management Strategies
1. Plant resistant varieties. Plums such as ‘President’, ‘Santa Rosa’, or ‘Fellinberg’.
2. Prune and destroy all knotted branches in the winter or before March 1. Prune 3–4 inches below the knot to remove all fungal material. Dip tools in a solution of 1–part bleach and 9–parts water between cuts.
3. Remove any wild cherry and plum trees surrounding your property. These trees may be harboring black knot and it spreads easily to cultivated varieties. Pruned material should be disposed of or burned.
4. Apply a fungicide cover spray at bud break. Pesticides registered for use include copper, chlorothalonil (Daconil), mancozeb, and thiophanate methyl (Cleary 3336).
Symptoms and Diagnosis
Initially the bark of infected twigs and medium-sized branches will begin to crack in the springtime. A light yellow discoloration and cork-like swelling occurs on infected areas. Knotted areas later turn an olive-green color and finally turn black and harden during the summer. The swelling weakens branches and may stunt or kill smaller branches due to decreased water and nutrient flow.
Life Cycle
Dibotryon morbosum is the fungus responsible for causing black knot disease on cherries and plums. Spores overwinter in the blackened "knots" of infected branches. Disease spores are spread to new hosts by wind during warm spring weather when temperatures are between 55–75 degrees F and there is rain or high humidity. Trees are weakened because the knots disrupt the normal flow of water and nutrients throughout the branches. Twig dieback is common.
Integrated Pest Management Strategies
1. Plant resistant varieties. Plums such as ‘President’, ‘Santa Rosa’, or ‘Fellinberg’.
2. Prune and destroy all knotted branches in the winter or before March 1. Prune 3–4 inches below the knot to remove all fungal material. Dip tools in a solution of 1–part bleach and 9–parts water between cuts.
3. Remove any wild cherry and plum trees surrounding your property. These trees may be harboring black knot and it spreads easily to cultivated varieties. Pruned material should be disposed of or burned.
4. Apply a fungicide cover spray at bud break. Pesticides registered for use include copper, chlorothalonil (Daconil), mancozeb, and thiophanate methyl (Cleary 3336).
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文章
Dummer. ゛☀
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.
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.
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.
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.
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.
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.
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.
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.
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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文章
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
Rust, Puccinia heterospora, is a fungal disease that infects leaves and stems of hollyhock. Lower leaves show the condition first, and the disease progresses upward during the growing season. The extent and severity depend on weather conditions.
Symptoms and Diagnosis
First symptoms appear on the leaves as individual, yellow, circular spots about one-eighth inch in size that enlarge to one-quarter inch or more in diameter. On the underside of the leaves, swellings or blisters soon emerge within these spots. At this stage, the symptoms resemble insect or mite galls found on many other plants; however, such galls are rare on hollyhock. The swellings continue to develop and in a few more days, they release masses of reddishbrown spores, covering the entire undersurface of the leaf.
You can easily identify the disease in the field by the round pustules that are covered by loosely attached red spores. Leaves that are heavily infected eventually turn gray or tan and die. Rust spots may also occur on the stems and leaf petioles and occasionally on green flower parts.
Life Cycle
The reddish spores are easily spread by splashing water, rain, and wind. The fungus overwinters in plant debris and possibly in overwintering, living plant tissue. Symptoms will appear very early the following spring when weather conditions are favorable.
Hollyhock rust is not extremely common throughout the state. Fortunately, we can usually enjoy colorful hollyhocks in spite of the disease, though the foliage may become unattractive in wet years.
Integrated Pest Management Strategies
1. Use disease-free plants.Start plants from seeds and place them some distance from infected stock.
2. Improve air circulation. Space plants out in a dry sunny location so that moisture is quickly evaporated from the foliage.
3. Keep plants healthy. Maintain the plants in a vigorous growing condition through a good fertility program. Irrigate during dry periods but keep the foliage dry, if possible.
4.Remove infested material. Remove old plant material and bury, burn, or compost it at the end of the flowering season. Picking off the first infected leaves as they appear may also be helpful. However, this practice alone often is not successful in controlling rust.
5. Control weeds. Destroy common mallow weeds in the vicinity as they may be hosts to the rust disease and a source of hollyhock infection.
6. Use fungicides if necessary. Consider using fungicides to supplement cultural control methods. Direct the applications primarily at the lower surface of the leaves and treat at approximately 7 to 10 day intervals. Reapply if rainfall exceeds 1/2 inch during the period. Pesticides registered for use include chlorothalonil (Daconil), sulfur, mancozeb, and maneb. All are protective fungicides and prevent rather than eradicate the fungus. Start using a fungicide prior to the first sign of disease development.
Symptoms and Diagnosis
First symptoms appear on the leaves as individual, yellow, circular spots about one-eighth inch in size that enlarge to one-quarter inch or more in diameter. On the underside of the leaves, swellings or blisters soon emerge within these spots. At this stage, the symptoms resemble insect or mite galls found on many other plants; however, such galls are rare on hollyhock. The swellings continue to develop and in a few more days, they release masses of reddishbrown spores, covering the entire undersurface of the leaf.
You can easily identify the disease in the field by the round pustules that are covered by loosely attached red spores. Leaves that are heavily infected eventually turn gray or tan and die. Rust spots may also occur on the stems and leaf petioles and occasionally on green flower parts.
Life Cycle
The reddish spores are easily spread by splashing water, rain, and wind. The fungus overwinters in plant debris and possibly in overwintering, living plant tissue. Symptoms will appear very early the following spring when weather conditions are favorable.
Hollyhock rust is not extremely common throughout the state. Fortunately, we can usually enjoy colorful hollyhocks in spite of the disease, though the foliage may become unattractive in wet years.
Integrated Pest Management Strategies
1. Use disease-free plants.Start plants from seeds and place them some distance from infected stock.
2. Improve air circulation. Space plants out in a dry sunny location so that moisture is quickly evaporated from the foliage.
3. Keep plants healthy. Maintain the plants in a vigorous growing condition through a good fertility program. Irrigate during dry periods but keep the foliage dry, if possible.
4.Remove infested material. Remove old plant material and bury, burn, or compost it at the end of the flowering season. Picking off the first infected leaves as they appear may also be helpful. However, this practice alone often is not successful in controlling rust.
5. Control weeds. Destroy common mallow weeds in the vicinity as they may be hosts to the rust disease and a source of hollyhock infection.
6. Use fungicides if necessary. Consider using fungicides to supplement cultural control methods. Direct the applications primarily at the lower surface of the leaves and treat at approximately 7 to 10 day intervals. Reapply if rainfall exceeds 1/2 inch during the period. Pesticides registered for use include chlorothalonil (Daconil), sulfur, mancozeb, and maneb. All are protective fungicides and prevent rather than eradicate the fungus. Start using a fungicide prior to the first sign of disease development.
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文章
Dummer. ゛☀
2017年09月16日
Powdery mildew is caused by a fungus and is seen as a light gray or whitish powder on the surface of leaves. It occurs following warm days and cool nights often being seen in the fall and spring. The disease is considered more unsightly than harmful. Death of the plant is rare.
Symptoms and Diagnosis
Even though each species of powdery mildew attacks only a narrow range of hosts, there are 11,000 species of the powdery mildew fungi, and many ornamentals are hosts. Superficial powdery patches appear on leaf surfaces, young stems, flowers, and even fruit. The powder is composed of mycelium and colorless chains of spores on upright stalks. Later there may be dark "pepper-like" spots among the powder (the spots are spore-producing bodies). As the disease progresses, leaves may be dwarfed, curl, turn yellow, and drop off. Flowers may be deformed. Fruit crops may be reduced, with the fruit misshapen and covered with powdery patches.
Life Cycle
Powdery mildew commonly winters over as mycelial mats in dormant buds or on plant stems and fallen leaves. During humid and warm spring weather (with cool nights), infected buds open and spread conidia (spores) to new host tissue. These conidia do not require free moisture in order to germinate as many fungi do. A new generation may be produced every 72 hours, if conditions are right.
Integrated Pest Management Strategies
1. Purchase resistant varieties. This is the best strategy for avoiding powdery mildew.
2. Pruning. Prune out diseased tissue and destroy it. Gather and destroy dead leaves and stems in the fall. This is the source of next season’s inoculum.
3. Keep plants in good vigor. Space the plants for good air circulation. Give the plants plenty of sun, as too much shade seems to make the problem worse. Try to avoid overhead watering and do not handle the plant when the foliage is wet as this will spread the disease. Water early in the day.
4. Fungicides. Use fungicides as a preventive treatment before a rain for maximum protection. Spray both sides of leaves and flowers well with sulfur, mancozeb, maneb, chlorothalonil (Daconil), cinnamaldehyde (Cinnamite), or copper-containing fungicides.
Symptoms and Diagnosis
Even though each species of powdery mildew attacks only a narrow range of hosts, there are 11,000 species of the powdery mildew fungi, and many ornamentals are hosts. Superficial powdery patches appear on leaf surfaces, young stems, flowers, and even fruit. The powder is composed of mycelium and colorless chains of spores on upright stalks. Later there may be dark "pepper-like" spots among the powder (the spots are spore-producing bodies). As the disease progresses, leaves may be dwarfed, curl, turn yellow, and drop off. Flowers may be deformed. Fruit crops may be reduced, with the fruit misshapen and covered with powdery patches.
Life Cycle
Powdery mildew commonly winters over as mycelial mats in dormant buds or on plant stems and fallen leaves. During humid and warm spring weather (with cool nights), infected buds open and spread conidia (spores) to new host tissue. These conidia do not require free moisture in order to germinate as many fungi do. A new generation may be produced every 72 hours, if conditions are right.
Integrated Pest Management Strategies
1. Purchase resistant varieties. This is the best strategy for avoiding powdery mildew.
2. Pruning. Prune out diseased tissue and destroy it. Gather and destroy dead leaves and stems in the fall. This is the source of next season’s inoculum.
3. Keep plants in good vigor. Space the plants for good air circulation. Give the plants plenty of sun, as too much shade seems to make the problem worse. Try to avoid overhead watering and do not handle the plant when the foliage is wet as this will spread the disease. Water early in the day.
4. Fungicides. Use fungicides as a preventive treatment before a rain for maximum protection. Spray both sides of leaves and flowers well with sulfur, mancozeb, maneb, chlorothalonil (Daconil), cinnamaldehyde (Cinnamite), or copper-containing fungicides.
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Dummer. ゛☀
2017年09月16日
Also called red spot or measles, this disease affects all aboveground parts of the peony. Caused by the fungal pathogen, Cladosporium paeoniae, this disease occurs each spring just before bloom. It is mostly found on older varieties and is not immediately lethal, though repeated bouts for several years will affect plant vitality. It does not cause early leaf drop or stem dieback but causes the plant to be unsightly and lose its attractiveness as spots coalesce to form blighted areas.
Symptoms and Diagnosis
Small, circular, red or purplish spots first appear superficially on the upper surface of young leaves. Later in the season they coalesce into large, glossy, irregular, dark purple blotches while the underside of the leaves becomes a dull chestnut brown. Short reddish-brown streaks appear on the young stems and petioles, and eventually the whole plant may be affected with purplish or brownish red spots.
Life Cycle
The late-season blotch phase provides the overwintering inoculum for the next year's infection, especially in older varieties. Fungicides work only to prevent infection; once the disease takes hold, there is no treatment.
Integrated Pest Management Strategies
1. Remove debris. Be sure to remove all foliage to ground level each fall and destroy. Infected debris should not be added to the compost pile.
2. Apply fungicides. When the shoots are 2–4 inches high and the weather is cool, overcast, and damp, spray weekly with a fungicide until the flowers open. Reapply following rain or overhead watering. Mancozeb is currently registered for controlling peony blotch.
3. Resistant varieties. Replant with newer resistant varieties that are vigorous and thick-stemmed.
4. Watering and air circulation. Provide good air circulation by proper spacing of plants and foliage thinning to reduce humidity and promote leaf drying. Water early in the day, so that leaves dry thoroughly by night; drip irrigation is best.
Symptoms and Diagnosis
Small, circular, red or purplish spots first appear superficially on the upper surface of young leaves. Later in the season they coalesce into large, glossy, irregular, dark purple blotches while the underside of the leaves becomes a dull chestnut brown. Short reddish-brown streaks appear on the young stems and petioles, and eventually the whole plant may be affected with purplish or brownish red spots.
Life Cycle
The late-season blotch phase provides the overwintering inoculum for the next year's infection, especially in older varieties. Fungicides work only to prevent infection; once the disease takes hold, there is no treatment.
Integrated Pest Management Strategies
1. Remove debris. Be sure to remove all foliage to ground level each fall and destroy. Infected debris should not be added to the compost pile.
2. Apply fungicides. When the shoots are 2–4 inches high and the weather is cool, overcast, and damp, spray weekly with a fungicide until the flowers open. Reapply following rain or overhead watering. Mancozeb is currently registered for controlling peony blotch.
3. Resistant varieties. Replant with newer resistant varieties that are vigorous and thick-stemmed.
4. Watering and air circulation. Provide good air circulation by proper spacing of plants and foliage thinning to reduce humidity and promote leaf drying. Water early in the day, so that leaves dry thoroughly by night; drip irrigation is best.
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Dummer. ゛☀
2017年09月16日
Angular leaf spot is a common bacterial disease of Goldsturm coneflower (Rudbeckia fulgida var. sullivantii 'Goldsturm')
Two common leaf spots affect rudbeckia in the St. Louis area. Both rarely endanger the survival of the plant but both can cause depreciation of the foliage. One is caused by a fungus and the other by a bacterium.
Symptoms and Diagnosis
Septoria leaf spot is caused by the fungus Septoria rudbeckiae and causes small 1/8 - 1/4 inch spots on the leaves. Small, black, pinpoint size fruiting bodies (pycnidia) form in the center of the spots. Lower leaves are affected first. The disease then moves up the plant by splashing water. Angular leaf spot of rudbeckia is most common on the cultivar 'Goldsturm'. It begins as small, brown, angular spots on lower leaves, which may appear water-soaked but can quickly expand to affect the whole leaf. It begins at the base of the plant and moves up. Angular leaf spot is caused by a bacterium. The absence of fungal pycnidia and the presence of bacterial streaming under microscopic examination can be used to differentiate angular leaf spot from septoria leaf spot.
Life Cycle
Both organisms overwinter in infected debris in the garden. Initial infection occurs in late spring or early summer on the lower leaves and then spread up the plant. Plants are rarely killed, but plants can look unsightly by early fall.
Integrated Pest Management Strategies
1. Clean up old foliage each fall and then live with the disease. Sanitation can go a long way to helping control both diseases. Collect and dispose of old foliage in the fall or by late winter to help prevent early infection.
2. Provide good air circulation and avoid overhead watering. Keeping the leaves dry and help prevent movement of the fungi or bacteria by not watering overhead. If irrigation is necessary, use soaker hoses or at least water early in the day so the foliage can dry before nightfall.
3. Apply chemical protectants. Septoria leaf spot can be controlled with fungicides containing chlorothalonil or copper. Angular leaf spot can be controlled by applying a copper-based fungicide such as Bordeaux mixture as needed started in early spring. Kocide is also effective. Apply at the first signs of disease to protect healthy yet unaffected foliage.
Two common leaf spots affect rudbeckia in the St. Louis area. Both rarely endanger the survival of the plant but both can cause depreciation of the foliage. One is caused by a fungus and the other by a bacterium.
Symptoms and Diagnosis
Septoria leaf spot is caused by the fungus Septoria rudbeckiae and causes small 1/8 - 1/4 inch spots on the leaves. Small, black, pinpoint size fruiting bodies (pycnidia) form in the center of the spots. Lower leaves are affected first. The disease then moves up the plant by splashing water. Angular leaf spot of rudbeckia is most common on the cultivar 'Goldsturm'. It begins as small, brown, angular spots on lower leaves, which may appear water-soaked but can quickly expand to affect the whole leaf. It begins at the base of the plant and moves up. Angular leaf spot is caused by a bacterium. The absence of fungal pycnidia and the presence of bacterial streaming under microscopic examination can be used to differentiate angular leaf spot from septoria leaf spot.
Life Cycle
Both organisms overwinter in infected debris in the garden. Initial infection occurs in late spring or early summer on the lower leaves and then spread up the plant. Plants are rarely killed, but plants can look unsightly by early fall.
Integrated Pest Management Strategies
1. Clean up old foliage each fall and then live with the disease. Sanitation can go a long way to helping control both diseases. Collect and dispose of old foliage in the fall or by late winter to help prevent early infection.
2. Provide good air circulation and avoid overhead watering. Keeping the leaves dry and help prevent movement of the fungi or bacteria by not watering overhead. If irrigation is necessary, use soaker hoses or at least water early in the day so the foliage can dry before nightfall.
3. Apply chemical protectants. Septoria leaf spot can be controlled with fungicides containing chlorothalonil or copper. Angular leaf spot can be controlled by applying a copper-based fungicide such as Bordeaux mixture as needed started in early spring. Kocide is also effective. Apply at the first signs of disease to protect healthy yet unaffected foliage.
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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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Dummer. ゛☀
2017年09月16日
Botrytis blight on peony foliage (Paeonia)
Gray mold or botrytis blight is caused by the fungus, Botrytis paeoniae. It is the most common disease of garden peonies. This destructive disease is very prevalent during damp, rainy seasons.
Symptoms and Diagnosis
On peonies afflicted with botrytis, the young shoots rot off at ground level when they are 5 to 8 inches tall. The stems often have a water-soaked, cankerous appearance. The leafy shoots wilt suddenly and fall over. The rotted portion of the plant will become covered with a soft brown or blackish mass of spores. Just above the ground level, the stalk will be covered with a gray mold which sheds large numbers of spores. The spores are carried by wind and insects to young leaves and flower buds and cause a leaf blight and bud rot. Small buds that are affected turn black and wither. Larger buds turn brown and fail to open. During a severe outbreak of the disease, 90% of the buds fail to develop. Open flowers are affected occasionally, and they also turn brown and later develop a covering of gray mold.
Life Cycle
Botrytis fungi are both saprophytic and parasitic. The spore-producing structures of the fungus develop along the base of the rotting stalks and survive in debris left in the garden over the winter. In the spring, spores form and spread to dying, wounded, or extremely soft plant tissues. As the disease progresses, a gray mold develops. The gray mold is made up of spores that are either wind-blown or splashed onto new tissues and infect.
Integrated Pest Management Strategies
1. Prevent infection. In early fall, cut down all old leaves and stalks to ground level. This debris should be destroyed and not composted. Apply 1 to 2 inches of mulch to bury debris.
2. Improve soil drainage. Plant peonies in welldrained soil; heavy clay soils should be lightened with organic material such as compost or peat moss. They should not be planted so that water is apt to cover their bases, nor should soil be heaped about the leaf bases.
3. Move plants to a better location. Good air circulation can reduce disease problems. Plant in full sun or at least in part sun. Space plants widely, at least 3 feet apart. Remove aging leaves from plants.
4.Use disease-free roots. When planting new plants, buy only from reputable dealers, or take divisions only from healthy, disease-free plants.
5. Use a fungicide. Spray the plants with a fungicide when young tips break through the ground. Follow 2 weeks later with another application and every 14 days thereafter until mid-June. 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.
6. Look for varieties that show some resistance to the disease.
Gray mold or botrytis blight is caused by the fungus, Botrytis paeoniae. It is the most common disease of garden peonies. This destructive disease is very prevalent during damp, rainy seasons.
Symptoms and Diagnosis
On peonies afflicted with botrytis, the young shoots rot off at ground level when they are 5 to 8 inches tall. The stems often have a water-soaked, cankerous appearance. The leafy shoots wilt suddenly and fall over. The rotted portion of the plant will become covered with a soft brown or blackish mass of spores. Just above the ground level, the stalk will be covered with a gray mold which sheds large numbers of spores. The spores are carried by wind and insects to young leaves and flower buds and cause a leaf blight and bud rot. Small buds that are affected turn black and wither. Larger buds turn brown and fail to open. During a severe outbreak of the disease, 90% of the buds fail to develop. Open flowers are affected occasionally, and they also turn brown and later develop a covering of gray mold.
Life Cycle
Botrytis fungi are both saprophytic and parasitic. The spore-producing structures of the fungus develop along the base of the rotting stalks and survive in debris left in the garden over the winter. In the spring, spores form and spread to dying, wounded, or extremely soft plant tissues. As the disease progresses, a gray mold develops. The gray mold is made up of spores that are either wind-blown or splashed onto new tissues and infect.
Integrated Pest Management Strategies
1. Prevent infection. In early fall, cut down all old leaves and stalks to ground level. This debris should be destroyed and not composted. Apply 1 to 2 inches of mulch to bury debris.
2. Improve soil drainage. Plant peonies in welldrained soil; heavy clay soils should be lightened with organic material such as compost or peat moss. They should not be planted so that water is apt to cover their bases, nor should soil be heaped about the leaf bases.
3. Move plants to a better location. Good air circulation can reduce disease problems. Plant in full sun or at least in part sun. Space plants widely, at least 3 feet apart. Remove aging leaves from plants.
4.Use disease-free roots. When planting new plants, buy only from reputable dealers, or take divisions only from healthy, disease-free plants.
5. Use a fungicide. Spray the plants with a fungicide when young tips break through the ground. Follow 2 weeks later with another application and every 14 days thereafter until mid-June. 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.
6. Look for varieties that show some resistance to the disease.
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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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Dummer. ゛☀
2017年09月16日
Distorted flowers on purple coneflower (Echinacea purpurea) caused by aster yellows
Aster yellows is a viral-like disease caused by a phytoplasma (formerly called a mycoplasma-like organism). Insects that suck the sap of plants, especially the aster leafhopper, vector the disease. Aster leafhoppers are insects that annually migrate northward from their winter home in areas along the Gulf of Mexico. Aster yellows is a disease that affects over 300 species of plants, including ornamentals such as aster, coneflower, zinnia, marigold, chrysanthemum, petunia, and snapdragon. Edibles affected include lettuce, carrot, tomato, and celery. Grasses and grains also are hosts. Weeds that may harbor the disease include plantain, dandelion, and other broad-leafed weeds.
Aster yellows is primarily transmitted by leafhoppers. When a leafhopper feeds on a plant infected with aster yellows it becomes "infected" with the phytoplasma and remains infected throughout its life. The phytoplasma cells multiply and cause infection of the insect’s salivary glands within one to three weeks. When the infected insects feed on healthy plants, they inject the phytoplasma cells into the plant phloem. Susceptible plants will be symptomatic in 10 to 40 days.
The spread of aster yellows is worse in cool, wet summers. Hot dry weather is not favorable for either the phytoplasma or the leafhopper. As with many disease and pest problems, diagnosis is perhaps the most important factor in controlling aster yellows.
A somewhat similar appearing problem on coneflowers is caused by an eriophyid mite. Experts are still sorting this problem out but the lower pictures on this page may be caused by this yet unnamed eriophyid mite. At present the common name used for this disorder is coneflower rosette mite. It may be a controllable problem through sanitation practices (disposal of all affected flowers as they appear and all foliage in the fall) unlike aster yellows for which there is no cure other than to destroy infected plants.
Symptoms and Diagnosis
Chlorosis, yellowing of the leaves while the veins remain green, is a major symptom of aster yellows. Growth slows down and leaves may be smaller and more narrow than usual. Foliage is sometimes curled. Flowers may be deformed and exhibit bizarre tufts of deformed leaves inside the flower or in place of the flower. Flowers may not produce seeds. The symptoms of the disease will often differ depending upon what species is infected. For instance, carrot roots may be bitter and hairy while lettuce may show pink or tan spots and have twisted inner leaves.
Integrated Pest Management Strategies
1. Remove diseased plants. Once a plant is infected with aster yellows, it is a lost cause since the disease is incurable. Early diagnosis and prompt removal of infected plants may help reduce the spread of the disease. Although the disease itself is not fatal to the plant, its presence makes it impossible for a plant to fulfill its intended role in the garden.
2. Plant less susceptible plant species. Controlling aster yellows is difficult. As long as infected leafhoppers are around, they can infect plants. A practical way to avoid having problems with this disease is to grow plants that are not as susceptible to aster yellows. Verbena, salvia, nicotiana, geranium, cockscomb, and impatiens are among the least susceptible plants.
3. Control insects. Vegetable growers may protect susceptible crops by using the mesh fabrics that keep leafhoppers and other insects away from the plants. Some growers put strips of aluminum foil between rows because bright reflections of sunlight confuse the leafhoppers.
4. Control weeds. Remove weeds in your lawn, garden, and surrounding areas, including plantain and dandelion that may harbor the disease.
Aster yellows is a viral-like disease caused by a phytoplasma (formerly called a mycoplasma-like organism). Insects that suck the sap of plants, especially the aster leafhopper, vector the disease. Aster leafhoppers are insects that annually migrate northward from their winter home in areas along the Gulf of Mexico. Aster yellows is a disease that affects over 300 species of plants, including ornamentals such as aster, coneflower, zinnia, marigold, chrysanthemum, petunia, and snapdragon. Edibles affected include lettuce, carrot, tomato, and celery. Grasses and grains also are hosts. Weeds that may harbor the disease include plantain, dandelion, and other broad-leafed weeds.
Aster yellows is primarily transmitted by leafhoppers. When a leafhopper feeds on a plant infected with aster yellows it becomes "infected" with the phytoplasma and remains infected throughout its life. The phytoplasma cells multiply and cause infection of the insect’s salivary glands within one to three weeks. When the infected insects feed on healthy plants, they inject the phytoplasma cells into the plant phloem. Susceptible plants will be symptomatic in 10 to 40 days.
The spread of aster yellows is worse in cool, wet summers. Hot dry weather is not favorable for either the phytoplasma or the leafhopper. As with many disease and pest problems, diagnosis is perhaps the most important factor in controlling aster yellows.
A somewhat similar appearing problem on coneflowers is caused by an eriophyid mite. Experts are still sorting this problem out but the lower pictures on this page may be caused by this yet unnamed eriophyid mite. At present the common name used for this disorder is coneflower rosette mite. It may be a controllable problem through sanitation practices (disposal of all affected flowers as they appear and all foliage in the fall) unlike aster yellows for which there is no cure other than to destroy infected plants.
Symptoms and Diagnosis
Chlorosis, yellowing of the leaves while the veins remain green, is a major symptom of aster yellows. Growth slows down and leaves may be smaller and more narrow than usual. Foliage is sometimes curled. Flowers may be deformed and exhibit bizarre tufts of deformed leaves inside the flower or in place of the flower. Flowers may not produce seeds. The symptoms of the disease will often differ depending upon what species is infected. For instance, carrot roots may be bitter and hairy while lettuce may show pink or tan spots and have twisted inner leaves.
Integrated Pest Management Strategies
1. Remove diseased plants. Once a plant is infected with aster yellows, it is a lost cause since the disease is incurable. Early diagnosis and prompt removal of infected plants may help reduce the spread of the disease. Although the disease itself is not fatal to the plant, its presence makes it impossible for a plant to fulfill its intended role in the garden.
2. Plant less susceptible plant species. Controlling aster yellows is difficult. As long as infected leafhoppers are around, they can infect plants. A practical way to avoid having problems with this disease is to grow plants that are not as susceptible to aster yellows. Verbena, salvia, nicotiana, geranium, cockscomb, and impatiens are among the least susceptible plants.
3. Control insects. Vegetable growers may protect susceptible crops by using the mesh fabrics that keep leafhoppers and other insects away from the plants. Some growers put strips of aluminum foil between rows because bright reflections of sunlight confuse the leafhoppers.
4. Control weeds. Remove weeds in your lawn, garden, and surrounding areas, including plantain and dandelion that may harbor the disease.
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Dummer. ゛☀
2017年09月15日
Leaves will become a dark brown colour and drop. Blossoms will die back. Fruits will become discoloured and wrinkled. A white slimy substance may excrete from infected areas. Often, the first time this disease becomes apparent is when new leaves do not appear in spring on deciduous trees and shrubs. Alternatively, woody plants may suddenly defoliate and die-back along their stems. Determining the cause as honey fungus can be tricky though. A clear indicator is the presence of strands of the fungus in the soil around affected plants. These look like thick black bootlaces. Pale brown or yellowish toadstools may appear in autumn and a gooey resin may be found oozing from the base of stems.
Plants affected
The most susceptible include: apples, crab apples, walnut, willow, wisteria, cotoneaster, rhododendron, roses and many conifers, including pine, cypress and thuja. In addition almost all garden trees and shrubs and some herbaceous plants can also succumb.
About Honey fungus
Honey fungus lives in dead tree stumps and spreads from there to healthy plants nearby.
There are a group of closely related fungi which are collectively known as honey fungus.
Honey fungus is notoriously difficult to diagnose as the symptoms are easily confused with other problems.
Honey fungus remains in the soil for years if allowed to establish.
Treatment
Chemical
There is currently no chemical control commercially available for honey fungus.
Organic
Remove diseased plants and dig out the roots as far as possible.
Do not replant with trees or shrubs for at least a year.
Remove and replace the infected soil from around the affected plant.
Where possible, have any large stumps removed from the garden.
When replanting, stick to resistant plants such as oak, ash, beech, yew, clematis, laurel or mahonia.
Prevention
Sterilise any tools used for removing infected material with a household bleach solution after every use
Plants affected
The most susceptible include: apples, crab apples, walnut, willow, wisteria, cotoneaster, rhododendron, roses and many conifers, including pine, cypress and thuja. In addition almost all garden trees and shrubs and some herbaceous plants can also succumb.
About Honey fungus
Honey fungus lives in dead tree stumps and spreads from there to healthy plants nearby.
There are a group of closely related fungi which are collectively known as honey fungus.
Honey fungus is notoriously difficult to diagnose as the symptoms are easily confused with other problems.
Honey fungus remains in the soil for years if allowed to establish.
Treatment
Chemical
There is currently no chemical control commercially available for honey fungus.
Organic
Remove diseased plants and dig out the roots as far as possible.
Do not replant with trees or shrubs for at least a year.
Remove and replace the infected soil from around the affected plant.
Where possible, have any large stumps removed from the garden.
When replanting, stick to resistant plants such as oak, ash, beech, yew, clematis, laurel or mahonia.
Prevention
Sterilise any tools used for removing infected material with a household bleach solution after every use
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文章
Dummer. ゛☀
2017年09月15日
Whiteflies are harmful to both outdoor and indoor plants by sucking plant sap. Under certain conditions, they can also transmit disease. The whitefly parasite (Encarsia formosa) lays its eggs — as many as 50 to 100 — in both pupae and later larval stages of the white fly, destroying them before they can become adults. The host larva turns black as the parasite develops. It emerges, depending on conditions, in about two weeks. The adults will also feed on the larval juices released when they puncture the larvae.
Shop our large selection of beneficial insects, including whitefly parasites, at Planet Natural. One strip of cards — 500 parasitic wasps — treats up to 250 square feet and costs $29.50 with USPS Priority Mail shipping included!
Attracted to the flies by the smell of the honeydew they produce, E. formosa is an efficient biological control of whitefly and one of the most cost effective ways to control greenhouse and indoor infestations of the pest.
Humidity and strong light encourage the parasite’s activity. Temperature is also key as the parasite will not fly and seek out new prey at temperatures under 62 degrees. Its preference for warm, humid, well-lit conditions make the whitefly parasite the perfect solution for indoor and greenhouse whitefly problems.
Depending on pest levels, the following release rates have been established:
2-4 per square foot of infested area
1-2 per plant when pests are first noticed
Whitefly parasites are shipped as mature pupae in host eggs, glued to a paper card and almost ready to hatch as adult parasitic wasps. If pest levels are high, use a least-toxic, short-lived natural pesticide (insecticidal soap, botanical insecticide) to establish control, then release beneficials 2-3 weeks later to maintain control.
Shop our large selection of beneficial insects, including whitefly parasites, at Planet Natural. One strip of cards — 500 parasitic wasps — treats up to 250 square feet and costs $29.50 with USPS Priority Mail shipping included!
Attracted to the flies by the smell of the honeydew they produce, E. formosa is an efficient biological control of whitefly and one of the most cost effective ways to control greenhouse and indoor infestations of the pest.
Humidity and strong light encourage the parasite’s activity. Temperature is also key as the parasite will not fly and seek out new prey at temperatures under 62 degrees. Its preference for warm, humid, well-lit conditions make the whitefly parasite the perfect solution for indoor and greenhouse whitefly problems.
Depending on pest levels, the following release rates have been established:
2-4 per square foot of infested area
1-2 per plant when pests are first noticed
Whitefly parasites are shipped as mature pupae in host eggs, glued to a paper card and almost ready to hatch as adult parasitic wasps. If pest levels are high, use a least-toxic, short-lived natural pesticide (insecticidal soap, botanical insecticide) to establish control, then release beneficials 2-3 weeks later to maintain control.
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