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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Gummosis is the oozing of sap from wounds or cankers on fruit trees. Gummosis can result from environmental stress, mechanical injury, or disease and insect infestation. Cytospora canker or Valsa canker, the fungal cause of gummosis, affects stone fruit trees like apricot, cherry, peach, and plum. Cytospora infection is distinguishable from insect damage and mechanical injuries because sawdust or pieces of bark are not mixed in the sap, as it would be with insect or mechanical damage. Cytospora canker is also known as perennial canker.
Symptoms and Diagnosis On trees infected with Cytospora canker, new shoots or leaves may turn yellow or wilt. Sunken lesions develop on the bark. These lesions enlarge, and gummy, amber-colored sap oozes from the bark. Curly orange threads (fungal chains) may grow out of the bark as the disease progresses. Leaves may brown and drop. The disease kills the wood underneath the cankers, often causing whole branches to die. Infected wood and the defoliation that may occur weakens the tree, but if the disease infects the trunk, the whole tree may die.
Life Cycle Cytospora canker is caused by one of two different fungi. The fungus overwinters on dead wood or in sunken lesions. Curly orange fungal chains will release spores in the spring which are distributed by winds and rain splash. Once the spores land on a host tree, they enter through wounds made from insect boring, mechanical injuries, or winter injury. Symptoms are more prevalent during warm (70–85 degrees F), wet spring weather as the moisture facilitates entry into wounds. Trees just coming out of dormancy are most susceptible to the pathogen.
Integrated Pest Management Strategies 1. Be careful not to damage trunks with lawn mowers or other yard and garden equipment. Fungal spores enter the tree through injured tissue where they germinate and penetrate the tissue. This is the primary mode of infection. 2. Take steps to prevent winter injuries. Plant in well-drained soils or amend soils to improve drainage as needed. Avoid planting in open or windy areas to reduce desiccation. Select winterhardy cultivars matched to your hardiness zone. Paint the lower branches and trunks of 1–3 year old trees with white latex paint to reduce cold damage.
3. Proper care and maintenance. Prevent insect boring damage by maintaining the health of the tree. Prune and dispose of diseased branches in late winter. Burn infected wood, if possible. 4. Plant more resistant varieties. None of these are immune, but fungal development is slower if the disease becomes established.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Gray mold of strawberries is caused by a fungus, Botrytis cinerea, which infects both the flowers and fruits. Because of this, Botrytis can greatly reduce fruit yields and is considered one of the most damaging diseases of strawberry. Botrytis is most prevalent during prolonged cool, wet weather during bloom and near harvest.
Symptoms and Diagnosis Blossoms commonly turn brown and die. A soft, light brown rot may appear on any part of the berry, but generally occurs first in the area of the cap, destroying the berry within 48 hours. The infected fruit spot is at first a light brown color and somewhat soft in texture. As the entire berry becomes infected, the rotted area becomes firm and turns a darker brown color. Fruits soon "mummify" and, like the blossoms, become covered with a gray, dusty powder which are the spores of the Botrytis fungus. Berries resting on damp soil or touching infected plant parts are most commonly infected.
Life Cycle Botrytis fungi overwinter as dark-colored, resting bodies (sclerotia) on dead tissue. In the spring during cool humid weather, spores form and spread by wind or water to wounded or extremely soft plant tissues. Infection can also occur from growth of fungal mycelium from previously infected plant parts. The fungus can survive on decaying vegetation so it can infect healthy plants throughout the growing season. Integrated Pest Management Strategies 1. Remove infected plant parts. Collecting and removing infected plant parts can slow the spread of the disease. This should be done frequently especially during fruit bearing time.
2. Improve air circulation around the plants. Space plants widely and prune leaves so that adequate air flow may speed drying of the vegetation. Work with plants when they are dry. 3. Avoid spring applications of nitrogen fertilizer. High nitrogen levels promote excessive leaf growth and available surfaces for infection. 4. Harvest regularly. Remove and dispose of rotten or severely damaged fruit throughout the season.
5. Move plants to a better location.Select sites for planting that have good air circulation, are not shaded, and not subject to frost injury. 6. Use fungicide sprays, if necessary. Apply a fungicide at 5–10% bloom and at full bloom. Fungicides may be reapplied every 7–10 days during wet seasons. Pesticides registered for use include captan, chlorothalonil (Daconil), copper, iprodione (Chipco), mancozeb, sulfur, thiram, and ziram.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Downy mildew is an extremely serious fungal disease of grapes that can result in severe crop loss. It is caused by the fungus Plasmopara viticola.
Symptoms and Diagnosis The pathogen attacks all green parts of the vine, especially the leaves. Lesions on leaves are angular, yellowish, sometimes oily, and located between the veins. As the disease progresses, a white cottony growth can be observed on the lower leaf surface. Severely infected leaves will drop. If enough defoliation occurs, the overwintering buds will be more susceptible to winter injury. Infected shoot tips become thick, curl, and eventually turn brown and die. Young berries are highly susceptible, appearing grayish when infected. Berries become less susceptible when mature. Eventually, infected berries will drop.
Life Cycle The fungus overwinters in diseased leaves on the ground. Spores are released in the spring and spread to the leaves and berries by splashing rain and wind. The fungus has two types of spores, both germinating into swimming spores. These spores swim to the stomates (breathing pores) of plants and initiate infection. Water is necessary for the spores to swim and infect, so outbreaks of the disease coincide with periods of wet weather. Downy mildew is favored by all factors that increase the moisture content of soil, air, and the plant, with rainfall being the principal factor for infection during the growing season. Downy mildew infection can become a severe problem when a wet winter is followed by a wet spring and a warm summer with frequent rainfall.
Integrated Pest Management Strategies 1. Maintain plant vigor. Make sure soils are welldrained. Fertilize according to soil test information obtained at least every other year. 2. Sanitation. Remove fallen leaves which are the source of overwintering inoculum. 3. Pruning. Prune out the ends of infected shoots.
4. Fungicides. Fungicides are an important control measure, especially on susceptible cultivars. They should be applied just before bloom, 7 to 10 days later (usually at the end of bloom), 10 to 14 days after that, and finally, 3 weeks after the third application. For cultivars very susceptible to downy mildew or where the disease was severe the previous season, an additional application is suggested about 2 weeks before the first blossom opens. Pesticides registered for use include captan, copper, fosetyl-Al, mancozeb, maneb, and ziram. 5. Cultivars. Select and plant resistant cultivars.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Cedar-apple rust (Gymnosporangium juniperivirginianae), cedar-hawthorn rust (G. globosum), and cedar-quince rust (G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Cedar-quince rust has the broadest host range and can affect many genera in the rose family including apple, crabapple, pears, quince, hawthorn, serviceberry, mountain-ash, flowering quince, cotoneaster, chokeberry, and photinia.
Symptoms and Diagnosis Symptoms on juniper: Perennial, elongated swellings on the tips of twigs and branches, which may crack and form cankers, are symptoms of cedar quince rust on red cedars and junipers. In damp spring weather, cushion-shaped, orange, gelatinous blisters burst through the bark where the branches are swollen. Cedar-quince rust disease damages the ornamental value of susceptible cedars and junipers, killing young branches and weakening plants when cankers occur on the main trunk.
Symptoms on apple and other hosts: Young branches and fruit (not leaves) are usually infected and symptoms vary widely among the various hosts. On hawthorn, the pinkish aecia (tubes) occur mainly on branches, thorns, and fruit. Hawthorn and serviceberry fruit often becomes heavily covered with aecia. Branch and thorn infections result in spindle-shaped, perennial cankers that expand each growing season. However, most infected branches are girdled by the canker during the second season, causing dieback to a bud or side-shoot.
Life Cycle Basidiospores that are released from the juniper gall telial swellings infect stems and fruit of quince and the other deciduous hosts. Seven to ten days after infection, spots or swellings develop, followed a few days later by the formation of tiny black dots within the spots. Four to seven weeks later, aecia are formed. Aeciospores, released from the aecia during rain or as morning humidity lowers, become airborne and infect susceptible junipers during late summer and fall. The following spring (or one year later), swellings (consisting of both fungal and host plant tissues) develop on the juniper host. When the swellings are mature, a few hours of wet, cool (74 to 78 degrees F) spring weather are sufficient for repeated telial swelling and the release of basidiospores that infect quince and other deciduous hosts. The cedar-quince rust galls may remain infectious for 4–6 years or more (up to 20), whereas the cedar-apple gall is only infectious for one year.
Integrated Pest Management Strategies 1. Prune. Prune out cankers associated with cedarquince rusts from landscape junipers and deciduous host plants. The spread of cedar-quince rust can be limited by reducing the infested plant parts. This is practical if a few plants are infected and the number of galls per plant is limited. 2. Co-exist. Live with the disease. It may disfigure plants when twigs are infected.
3. preventive fungicide. Use preventive fungicides labeled for use on quince and other hosts. Fungicide sprays are aimed at protecting developing twigs and branches from infection during the time the galls on the junipers are orange and gelatinous. This usually lasts for several weeks and fungicide applications are not necessary once the galls become dry and inactive. Always read and follow label directions. Pesticides registered for use include captan, chlorothalonil (Daconil), mancozeb, sulfur, thiram, and ziram.
4. Avoid planting susceptible plants together. Do not plant junipers close to susceptible varieties of apples, crabapples, or quince. 5. Resistant varieties. Remove and replace diseased plants with resistant varieties.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Cedar-apple rust (Gymnosporangium juniperivirginianae), cedar-hawthorn rust (G. globosum), and cedar-quince rust (G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Cedar-hawthorn rust, in addition to affecting apples, crabapples, and many hawthorns sometimes infects pears, quince, and serviceberry.
Symptoms and Diagnosis Symptoms on juniper: The fungus produces reddishbrown galls on twigs and small branches of susceptible junipers. After reaching a diameter of about 1/8 to 1/2 inch, circular dimple-like depressions will appear resembling the surface of a golf ball. In the spring, small chestnut brown structures protrude from each of the dimples. During wet spring weather, these projections greatly expand into an orange mass of spore-bearing, jelly-like tendrils known as telial horns. Blown by the wind, the microscopic spores infect neighboring hawthorn trees. The galls produce spores at least two years in succession after which they dry out and harden. They can remain on the juniper host for several years.
Symptoms on hawthorn: Cedar-hawthorn rust causes discoloring and yellow to nearly black spots on the leaves, fruit, petioles or new twigs. These spots contain black pimple-like fruiting bodies that produce spores. Life Cycle The disease overwinters as galls on infected junipers. During wet spring weather, "horns" extrude from the galls and produce spores. These spores are then windblown or carried by insects to the leaves of nearby susceptible hawthorn plants. The spores then turn brown, infect the leaf tissue, and form yellow spots on the leaves. In the late summer, spores are produced on hawthorn leaves. They are windblown back to needle bases or cracks in juniper twigs. After infection of the juniper, small galls form, thus completing the cycle. It takes two years to produce a spore-bearing gall.
Integrated Pest Management Strategies 1. For both hawthorns and junipers, prune out diseased branches. The spread of cedar-hawthorn rust can be limited by reducing infested plant parts. 2. Live with the disease. The disease rarely kills trees. It can, however, disfigure plants when twigs are infected. 3. Use fungicidal sprays. Both junipers and hawthorns can be protected from infection with fungicide applications during periods of spore production. Spray hawthorns prior to spring bloom with a fungicide. Pesticides registered for use include chlorothalonil (Daconil) and mancozeb. Thorough uniform coverage of plant surfaces is essential for good disease control. Spray foliage to the point of runoff. Repeat on a 7–10 day schedule while cloudy and/or wet conditions favorable for disease development are common. Spray junipers three times, at two-week intervals, beginning in mid-July, with a fungicide such as Acme Bordeaux Mixture.
4. Avoid planting susceptible hawthorns within a two-mile radius of junipers. (This may be impractical in an urban environment.) 5. Replace infected trees with genetically resistant hawthorn varieties.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
Cedar-apple rust (Gymnosporangium juniperivirginianae), cedar-hawthorn rust (G. globosum), and cedar-quince rust (G. clavipes) are closely related rust diseases that require two hosts to complete their life cycle. All three rusts can infect most varieties of eastern red cedar (Juniperus virginiana) as well as many other junipers and an alternate host. Of these alternate hosts, cedar-apple rust is primarily a disease of apples and crabapples. Cedar-hawthorn rust, in addition to affecting apples and crabapples, sometimes infects pears, quince, and serviceberry. Cedar-quince rust has the broadest host range and can infect many genera in the rose family. In addition to those plants already mentioned, mountain-ash, flowering quince, cotoneaster, chokeberry, and photinia are also hosts for this disease.
Symptoms and Diagnosis Symptoms on juniper: Brown, perennial galls form on twigs. When mature (usually in two years), the galls swell and repeatedly produce orange, gelatinous telial horns during rainy spring weather. The galls of cedar-apple rust are often over 2 inches in diameter, while cedar-hawthorn rust galls are rarely over 2 inches in diameter. Occasionally the twig beyond the gall dies, but usually no significant damage occurs on the juniper host. Symptoms on apple (or crabapple): Circular, yellow spots (lesions) appear on the upper surfaces of the leaves shortly after bloom. In late summer, brownish clusters of threads or cylindrical tubes (aecia) appear beneath the yellow leaf spots or on fruits and twigs. The spores associated with the threads or tubes infect the leaves (needles) and twigs of junipers during wet, warm weather.
Life Cycle On juniper, galls appear about seven months after infection, and they form gelatinous masses of spores after 18 months. Golf ball-like depressions form on the gall that will give rise to telial horns the following spring. The telial horns are brownish in color, but rapidly elongate and become bright orange with spring rain, shrinking and swelling with intermittent rainfall. After releasing their spores, the horns collapse, dry, and eventually fall off. The galls die at this point, but may remain attached to the juniper for a year or more. This rust is very obvious on red cedar and other junipers during spring, when the galls are covered with orange-brown gelatinous masses. Rust spores formed on the gelatinous masses cannot infect other junipers but can infect only certain susceptible species of the rose family.
On apples and crabapples the circular, yellow lesions on the upper surfaces of the leaves appear shortly after bloom. Wet, rainy weather in early spring is conducive for twig, leaf and fruit infection of these deciduous hosts. Heavy rains within the first two weeks of budbreak and leaf expansion cause the disease to be more severe. As the disease progresses, the undersides of the leaves below the yellow spots will develop raised orange structures that will ooze from the center, turn black, and appear as black dots. In late summer, this area will produce the orange and brown rust-colored spores that infect the juniper host, completing the cycle. Severely infected leaves may drop prematurely, especially during a dry summer.
Integrated Pest Management Strategies 1. Prune. Prune out the galls on junipers, if you wish, though be advised that the effectiveness of pruning out the galls or removing junipers is debatable since spores can travel long distances with the wind. 2. Co-exist. Live with the disease. It rarely kills trees. It may disfigure plants when twigs are infected. 3. Preventive fungicide. Use preventive fungicides labeled for use on apples. Fungicide sprays are aimed at protecting developing foliage from infection during the time the galls on the junipers are orange and gelatinous. This usually lasts for several weeks and fungicide applications are not necessary once the galls become dry and inactive. Pesticides registered for use include captan, chlorothalonil (Daconil), copper, mancozeb, maneb, sulfur, thiophanate methyl (Cleary 3336), thiram, triadimefon, and ziram.
4. Mixing plants. Avoid planting juniper and rust-susceptible hosts in close proximity to each other. 5. Resistant apple varieties. Use only resistant varieties in planting. Remove and replace diseased plants with resistant varieties.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
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.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
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.
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
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).
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Dummer. ゛☀
2017年09月17日
Dummer. ゛☀
The fungus, Armillaria mellea, occurs sporadically in this region and has been reported to infect over 25 species of ornamental trees and shrubs. The most distinctive sign of Armillaria infection is the honeycolored mushroom that grows from the roots and base of plants. The fungus is especially prevalent on oak but also affects many different kinds of fruit and nut trees, ornamentals, and herbaceous plantings. It is often referred to as oak root rot fungus because it is commonly found on oaks or in areas where oaks trees once were grown, such as cleared forest land.
Symptoms and Diagnosis The symptoms of Armillaria are similar to those of other root disorders; height growth is reduced, foliage is sparse, and leaves that remain on plants are stunted and yellow. An abnormal flow of sap may be visible on the root collar. When soil is removed from the base of the trunk, black, root-like strands are visible and attached to larger roots. White to dark, fan-shaped mats of fungal strands develop between the bark and wood in infected root and trunk tissues. The most positive sign of infection is the production of clusters of honey-colored mushrooms at the base of the tree near the soil line. The mushrooms may have stalks 4 to 6 inches high with caps 1 inch high and 2 to 4 inches wide.
Life Cycle Armillaria is found in the soil sporadically throughout the Midwest. The fungus spreads primarily by root-to-root contact or by root-like fungal strands. Root-like fungal strands grow through the soil and adhere to the host roots or root collar that it encounters. Successfully attacked trees do not die until infections girdle the base of the tree. On healthy, vigorous trees, Armillaria is not lethal but if present, it may begin to grow when the tree dies of other causes. Young trees are more likely to be killed by Armillaria. Trees that are 15–20 years old are more tolerant to attack.
Integrated Pest Management Strategies 1. Remove and destroy infected material. Remove as much of the stump as possible. Sterilize tools with a solution of 1–part bleach with 9–parts water after use. 2. Provide adequate moisture in a well-drained soil to maintain vigor and resistance to infection. Plants suffering from drought are extremely susceptible to infection. Fertilize trees appropriately in late winter or early spring.
3. No effective chemical controls are known. Plants reported by Auburn University to be resistant to Armillaria root rot include ginkgo, tulip tree, ash, bald cypress, cherry, Chinese elm, Chinese pistache, crabapple, cryptomeria, dawn redwood, eucalyptus, hackberry, holly, incense cedar, Leyland cypress, maidenhair tree, maple, privet, smoke tree, sweetgum, tree-ofheaven, white fir, and wisteria. These should be considered for replacement of diseased trees. New soil should be used to amend the planting site. All diseased material and associated roots, as much as possible, should be excavated before replanting.
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