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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
This pest is the most serious pest of this evergreen plant. It occurs everywhere in the USA from the East to the West coast. All varieties of boxwood are susceptible but the slower-growing English varieties are less susceptible than the American cultivars. The leafminer feeds between the upper and lower sides of the leaf.
Symptoms and Diagnosis The larvae feeding between the upper and lower parts of the leaf causes blisters on the underside of the leaf. The leaves infested by this pest become yellow and smaller than a normal leaf. When the plant is severely infested, it appears completely unhealthy.
Life Cycle Boxwood leafminers over-winter as partially-grown larvae in the leaf blisters. When the days warm in spring, the larvae become active and grow rapidly feeding between the upper and lower leaves for the balance of the summer. In May the adults force the pupal skin out of the mine, where it hangs for a few days after the fly, a gall midge, emerges. The adult leafminer is a yellow to orange-red fly that looks like a mosquito. Adult flies swarm around boxwoods about the time that the Weigelas bloom. When the boxwood’s new growth appears in spring, the females mate, then insert their eggs into the underside of the leaves. The adult fly dies soon after. The eggs hatch in about 14-21 days into the larval stage ( a maggot) that grows and feeds for the rest of the summer. The leaves develop the characteristic blisters as the larvae feed. The larvae then develop into orange pupae which darken before the adults emerge. One generation of the pest occurs each year.
Integrated Pest Management Strategies 1. Select resistant cultivars. Culltivars of English boxwood such as Buxus sempervirens 'Pendula,' '‘Suffruticosa,' 'Handworthiensis,' 'Pyramidalis,' 'Argenteo-varigata' and 'Varder Valley' are more resistant. 2. Natural controls. Encourage natural predators such as green lacewings and spiders. Maintain plant vigor since healthy plants are more tolerant of insect damage. 3. Mechanical controls. Prune the foliage before adults emerge or right after adult flies lay their eggs in May. This reduces the overall population of the leafminer. Pinch leaves hard enough to kill maggots in the infested leaves when practical.
4. Chemical insecticide control. If you choose to use a pesticide, apply when the new leaves are fully formed, around May 1st when the Weigela is in bloom. Make a second application between mid-June and mid-July. Use carbaryl (Sevin) or malathion to control adult flies. Acephate (Orthene) applied in mid-May (about 3-4 weeks after the adults emerge.) can be applied to control the larvae developing in the new leaves. In February to early April, the systemic insecticide imidacloprid (Merit) can be applied around the base of the shrub.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Bagworms, Thyridopteryx ephemeraeformis, produce conspicuous spindle-shaped cocoons on trees and shrubs throughout the United States. Bagworms feed on over 128 plant species. The most commonly attacked plants are arborvitae, red cedar, and other juniper species. They will also feed on fir, maple, juneberry, buckeye, persimmon, ginkgo, honeylocust, larch, sweet gum, spruce, pine, sycamore, poplar, oak, locust, willow, and hemlock.
Symptoms and Diagnosis The principle harm done by the insect is the destruction of foliage by the caterpillars. Plants usually are partially defoliated, weakened, and rendered unsightly. Complete defoliation can occur. The most notable sign of bagworm infestation is the presence of protective bags attached to a branch. The bags incorporate bits of twigs and leaves from the host plant. They are approximately 1 to 2 inches long and resemble Christmas tree ornaments hanging from the limbs.
Life Cycle The adult female bagworm does not look like a moth and never leaves her bag. She is maggot-like in appearance, soft-bodied, and yellowish-white. A mated female lays between 500 and 1000 eggs within the bag, after which she dies. The eggs remain inside the bag throughout the winter until they hatch the following spring. There is one generation a year. From late May to mid-June, bagworm larvae (caterpillars) begin emerging from the bags. Almost immediately after emerging, a larva starts to produce its own protective bag. The bag is constructed such that the larva's head and legs are free. This construction allows the larvae to move about the plant as it feeds on the foliage. As the larva grows, it increases the size of its bag. The full-grown larvae are about one inch long.
When a host plant becomes defoliated, the larvae will crawl off it with their bags and search for a new plant to feed upon. In mid-August, the mature larvae stop feeding and attach their bags to a twig. They close up the bag and pupate. By mid-September, the bagworm has completed its development, and adult males begin emerging from their bags. The male moth has a black, furry body and feathery antennae. The wings are almost transparent and have a span of about one inch. Integrated Pest Management Strategies 1. Handpick the bags. The most economical method of controlling bagworms is to handpick the bags and destroy them. Some birds and insect predators feed on larvae, so light infestations on large, healthy plants are usually controlled by natural means. On large plants, monitor infestations before resorting to chemical sprays. If the problem doesn't get worse, spraying is not required.
2. Use biological controls. In spring, as soon as eggs hatch and the young emerge, spray with Bacillus thuringiensis (Bt). Bt is a bacterium that causes the larvae to become sick, stop feeding, and later die. In St. Louis, the eggs hatch in late May to mid-June, or about the time the cigar tree, Catalpa speciosa, is in full bloom. 3. Use chemical controls. Because bagworms form protective bags very early, contact insecticides, while useful, are less effective than stomach poisons. For best control, spray when insects are young. Chemical controls become less effective as the bagworm matures. Chemical controls include acephate (Orthene), cyfluthrin and spinosad.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
The eastern white pine, Pinus strobus, is a fast growing, easily transplanted tree. It can become quite large, requiring sufficient room to develop properly. White pine needles are bluish-green to medium-green with five per bundle, about 4 inches long, very thin, and not stiff. Used as a windbreak, the limbs are brittle and may suffer wind damage which can help lead to decline of the tree. In general, symptoms of decline include some pattern of needle yellowing or browning, shriveled bark on trunk and branches, oozing sap, and in some cases, death of the tree. Affected trees can range from 2 feet to 20 feet or more. The main factor is root decline.
Symptoms and Diagnosis Inspect the roots for brown discoloration and the outer layer pulling off or not present. If the roots are white and healthy, then there are other problems. Other symptoms will be yellowing or browning of the needles and a limp appearance. Do not, however, confuse this with the normal yellowing and shedding of just older needles that occurs annually in the fall. The bark of the trunk and branches may shrivel and ooze sap. White pines suffer under conditions of urban stress, resulting in decreased vigor, less branching, shorter needles, and noticeable foliage chlorosis.
Life Cycle There is no life cycle as the problem is environmental. There can be many contributing factors, one of which is air pollutants. Other factors can be soil pH, water-logged soil, drought, flooding, heat, and sudden extremes in temperature and moisture. Heat is a main consideration. Even though white pine grows from USDA Zone 3 to 8, it does not appear to thrive in the hot humid areas. Possible use as an understory tree in these areas may help it survive. A white pine in poor health can be attacked by two root pathogens which can speed the decline of the tree; however, they are not the cause of decline. These pathogens are Phytophthora and Verticicladiella. Fungicides are not recommended as the fungi are not the cause of the tree decline.
Integrated Pest Management Strategies 1. Maintain plant vigor. When planting the tree, insure that the soil is moist, rich, well-drained, and on the acid side. The white pine can tolerate full sun though it will perform better in partial shade. Avoid hot, west-facing sites. 2. Select the planting area carefully. Do not use white pines as a windbreak. Since the branches are brittle, they can be damaged, causing stress in the tree. The brittleness can also lead to damage from snow and ice. Do not plant along roadways as salt spray is injurious to the tree. The tree is also subjected to ozone stress which causes needle tips to brown.
3. Planting time. White pines are best planted in spring. If fall planting is done, care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and consider application of an anti-desiccant during early winter. Avoid using winter salt on roadways and paths especially where traffic is high. 4. On-going care. Make sure the soil is adequately drained and that the tree is watered in periods of drought. Fertilize with an acid-type fertilizer like ammonium sulfate.
5. Removal. Prompt removal of white pines suffering from decline is not required as they will not infect surrounding pines.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Sphaeropsis tip blight is caused by the fungus, Sphaeropsis sapinea (also known as Diplodia pinea). It is one of the most destructive fungal diseases of pine trees in the Midwest. It is most common on Austrian pine but can also damage Scotch pine (Scots pine), ponderosa, and mugo pine. If not controlled, over a period of years, it will weaken and perhaps kill the tree.
Symptoms and Diagnosis Tip blight most commonly affects trees 13 or more years old that bear mature pine cones, but it can also affect younger trees. The most obvious symptom is the browning and stunting of the needles of the new growth. The needles are retained on the tree. Excess resin flow builds up on the dead twigs and needle bases. Small black pimples (pycnidia) about the size of fly specks are very noticeable on the bases of the browned needles, on the dead twigs, and on the cone scales. The pimples are the fruiting bodies of the fungus. Infection usually begins on the lower branches and moves up the tree. Sphaeropsis tip blight may be confused with pine tip moth damage. In the case of the latter, the fungal fruiting bodies will not be present, but moth larvae and tunneling in the shoots will be evident.
Life Cycle Symptoms of tip dieback are most common in spring from April to mid-June when the young emerging needles are soft and tender. They are most vulnerable for the two weeks when the buds first open. Spores are released from the fruiting bodies (pycnidia) and are moved by splashing rain, wind, animals, and pruning equipment. They are dispersed throughout the year. Under very moist, humid conditions, the spores germinate and infect the needles. Once the fungus infects the needles, tissue is destroyed and shoots and needles are stunted. Infected second-year cones are a major source of inoculum. Infected cones are often observed on plants that show no other signs of infection. Latent infection is common and may be symptomless.
Integrated Pest Management Strategies 1. Keep trees healthy. Weakened trees are more susceptible to disease. Water during dry periods and fertilize according to soil test recommendations. Spores of Sphaeropsis sapinea are ever-present and can be found on the branches of most pine trees with the exception of white pine. Spores can infect without causing symptoms.
2. Use fungicidal sprays.Infection of new shoots may be reduced significantly with properly timed fungicidal sprays. Fixed copper or Bordeaux should be applied twice during the period when buds are opening. Apply in late April to early May, when the buds just begin to open. Repeat application in one to two weeks. Other pesticides registered for use include chlorothalonil (Daconil), mancozeb, and thiophanate methyl (Cleary 3336). 3. Replace with more resistant trees. When dead or dying trees are removed, replant with trees that are less susceptible to Sphaeropsis tip blight such as white pine, spruces, or junipers.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Injury due to salt is most common on landscape plants growing adjacent to highways, streets, sidewalks, and driveways that are regularly salted during the winter for ice control. Most of the salt used for deicing purposes is sodium chloride, ordinary rock salt or table salt. On highways, the major problem to plants is caused by salt spray kicked up by fast moving traffic on wet, salted roads. The salt spray is deposited on adjacent plants causing dehydration of evergreen leaves. In the city, the major problem is salt runoff washing into the soil. Salt in the soil may be absorbed by the roots and cause direct toxic effects.
Symptoms and Diagnosis Salt spray causes bud death and twig dieback. Subsequent shoot growth at the branch base produces clusters of twigs known as "witches' brooms." Symptoms typically become evident in the spring. In evergreens and conifers, salt spray causes leaf browning or yellowing, needle tip flecking, and twig dieback. Salt in the soil is slower acting and may not affect plants for several years. Symptoms include an initial blue green cast to the foliage, marginal leaf burn or needle tip burn, reduction in leaf, flower and fruit size, premature fall coloration and defoliation, stunting, and a general lack of vigor. The symptoms often become evident in late summer or during periods of hot dry weather.
Integrated Pest Management Strategies 1. Reduce salt use. The most important method of preventing salt injury to plants is reducing the amount of salt used for deicing. Pure salt should never be applied. Salt should always be mixed with an abrasive such as sand, cinders, or ash. This combines the melting power of the salt with the grittiness of the abrasive so less total salt is needed. Commercial deicing products containing calcium chloride may be used instead of rock salt. These products will not damage the soil but will still injure plants, so they too should be mixed with abrasives and applied with the same precautions.
2. Apply salt carefully. Application should be limited to high risk locations such as high speed roads, intersections, hills, steps, and walkways. Avoid spilling or applying in heaps. 3. Leach salted soils. If salt has already entered the soil, water these areas heavily in the spring to help leach the salt out of the soil. This method, however, is only effective on well-drained soils. It is not effective on fine textured, compacted soils where water does not drain readily. 4. Protect plants. Plants may be protected from salt spray by placing materials such as plastic, burlap, plywood, or window screen on or in front of them. This provides a physical barrier that prevents salt spray from contacting the plant.
5. Avoid planting in drainageways or in areas where runoff collects. Salt spray damage can be avoided by planting trees and shrubs away from the spray drift zone, at least 50 feet from a highway or further if downwind. Plants vary in their sensitivity to salt. It should be emphasized that even tolerant plants are not immune to injury.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Rhizosphaera needlecast is caused by the fungus, Rhizosphaera kalkhoffii. The disease causes death and casting (dropping) of needles in spruces, especially Colorado spruce and occasionally white spruce. It is usually first evident on the lower branches of the tree and can cause severe defoliation and death of branches if allowed to persist. It rarely kills the tree.
Symptoms and Diagnosis Infections take place in the spring, and symptoms show up about a year later. Infected 2-year old needles become spotted or mottled, some turning yellow and some developing a purplish brown color in late summer. Browning becomes general in late winter to early spring, and needles are prematurely shed during summer and fall, 12 to 15 months after initial infection. Black fruiting bodies are visible on discolored needles and even some green ones. The spores emerge from the stomates on the needles so appear in rows along the needles. Scattered lower branches are usually affected first and then browning progresses upward. Symptoms may be confused with spider mite damage. In the latter, mites and fine webbing may be visible; the lines of black fruiting bodies on the needles will also be absent.
Life Cycle Rhizosphaera kalkhoffii overwinters in infected needles on the tree or ground. Spores are released from the infected needles in the spring, during wet weather. Spores are dispersed by splashing and dripping water. They infect newly emerging needles, as well as mature needles. Infection begins in spring, in April or May. Optimal temperature for fungal development on wet foliage is 77° F. Infection will occur in 48 hours if spores are present. Prolonged wetness can induce extensive infection.
Integrated Pest Management Strategies 1. Select healthy plants. If spruce trees are dropping their needles, avoid using these trees in the landscape. 2. Remove infected needles and branches during dry, sunny weather. Prune out diseased branches and rake up fallen needles. Burn or remove the collected debris. Disinfect pruning tools between cuts by dipping in a 10% chlorine bleach solution. Oil tools when done to inhibit rust. 3. Avoid overhead watering.Water on the foliage can promote infection. Spores require moisture to germinate and infect.
4. Improve air circulation to allow needles to dry more quickly. Maintain open spacing when planting or by mowing grass or brush. 5. Use fungicidal sprays. Severe infections should be sprayed with chlorothalonil (Daconil), thiophanate methyl (Cleary 3336), or copper-containing fungicides registered for use against this disease. Spray when the needles are half-elongated and again when fully elongated. A minimum of two years of treatment is recommended because of the organism's life cycle.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Procera root rot also known as white pine root decline is caused by the fungus Leptographium procerum (syn. Verticicladiella procera). It infects the inner bark and sapwood of the roots and lower trunk of white pine. Although the disease is most serious on white pine, it can also kill Scots and Austrian pines.
Symptoms and Diagnosis In the Spring, trees, aged 3 to 15 years, which have been infected for several years, show delayed bud break and reduced candle elongation. Mature foliage then fades, droops, and turns brown, in stark contrast to healthy trees nearby. Mortality appears to be at random with a few trees dying each year. Resin flow is visible at the tree base and is associated with a girdling chocolate brown to dark olive-brown canker under the bark. The trunk may be flattened on the affected side. Galleries of insects such as the pine root collar weevil may be found in the canker and provide a place for the fungus to sporulate. Weevils and other bark-infesting insects may serve as vectors for this disease. Although the fungus does not survive well in the soil, it may be spread by contaminated insects as they emerge from diseased trees and feed on healthy trees nearby.
Integrated Pest Management Strategies 1. Planting. Avoid planting eastern white pine on wet sites. Trees planted on wet sites seem to be more susceptible to the fungus. Excessively dry sites also seem to predispose trees to attack.
2. Sanitation. Remove and destroy infected trees including stumps, if possible. Do not replant eastern white pine among the stumps of recently killed trees. 3. Replant. If trees need to be replaced, do not plant a pine. Use arborvitae or spruce.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
The pinewood nematode, Bursaphelenchus xylophilus, kills conifers, especially pines, of many species. This pest is endemic throughout the eastern half of the United States. Scotch pine (Scots pine) is the most commonly affected host. The nematode is transmitted by sawyer beetles, a wood-boring bark beetle, through their feeding wounds into the resin canals. Here, the nematode will reproduce and hinder the movement of water through water-conducting tissues, eventually causing the plant to wilt. Locally destructive outbreaks have occurred in forest and landscape plantings of non-native pine species in Missouri and Illinois.
Symptoms and Diagnosis Early symptoms of pine wilt are often inconspicuous or slight, giving way to a rapid decline. The first visible symptoms usually include fading green color and/or slight yellowing of limbs. This may be evident on one or a few branches or may develop on all simultaneously. In addition, within 48 hours after infection, there will be a visible loss of resin flow as observed on a cut twig. Trees often die so rapidly that brown needles continue to cling to the twigs. Diseased pines commonly die in early summer or early fall; some species require 2 seasons. Confirmation of the disease is done by microscopic detection of the pathogenic nematode in an examination of infested wood samples from the main trunk or affected branches. For diagnostic purposes, branch samples should be not be less that one inch in diameter and collected from freshly killed areas where needles are brown, but still attached.
Life Cycle Once a susceptible host plant has been inoculated with the pinewood nematode via bark beetle feeding, the nematode will feed and multiply in the resin canals. Populations of 1,000 nematodes per gram of wood may occur when foliar symptoms appear. When plant stress factors, such as high temperatures, drought, or attack by other pathogens, increase, nematode populations will rise. After the host plant dies, the nematode will transform into a non-feeding form and this stage can be picked up by wood-feeding bark beetle larvae. This dispersive stage of the nematode will migrate to the pupal chambers of the bark beetle, then enter the bodies of newly formed bark beetle adults that will seek other tree hosts, and repeat the nematodes’ life cycle.
Integrated Pest Management Strategies 1. Removal. Quick removal of an infected tree is important in order to break the nematodes’ life cycle. Infested wood should be burned or buried (not chipped and used as mulch) to prevent reproduction and overwintering of the bark beetles in infested wood. Periods of high temperatures in summer favor epidemics, as do periods of severe drought, but little else is known of factors that favor or prevent epidemics of pine wilt. 2. Select resistant varieties. Consistent with geography and climate, select evergreen trees that are more resistant to the pinewood nematode. These would include eastern hemlock; blue, Norway and Serbian spruce; and Jeffrey, pitch, Virginia, shortleaf, loblolly, and Eastern white pine. Avoid the more susceptible species such as Scotch pine (Scots pine), Austrian pine, Japanese black pine, Japanese red pine, jack pine, mugo pine, and long-leaf pine.
3. Maintain healthy trees. While even a healthy tree may become infested with the pinewood nematode, stressed trees are more attractive to bark beetle feeding. Watering during extended drought periods, periodic light fertilization, and avoiding damage to the root system through construction or traffic will all reduce the chances of borer infestation and nematode transmission.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Pine needle rusts are caused by over 20 species of Coleosporium the most common being C. asterum. It results in browning needles and the loss of lower branches. It is rare in the St. Louis area but may affect Austrian, jack, red, Scots, mugo, and ponderosa pines.
Symptoms and Diagnosis The first sign of the disease is small yellow spots on the needles in fall and throughout the winter. In spring the spots develop spore-producing structures and the needles brown and die resulting in needle drop and the loss of lower limbs. Young pines are most affected.
Life Cycle Pine needle rust requires an alternate host to complete its life cycle. Goldenrod and asters are most common. Infection on pine needles begins in late summer or early fall when spores released from the fungus growing on goldenrod or asters infects the needles causing small yellow spots. The fungus grows inside the needle where it overwinters. The following spring the fungus resumes growth and the yellow spots develop into white swelling, which grow well above the needle surface. At this time the disease may be confused with pine needle scale. The spore-producing structures split open and release orange colored spores, which then infect goldenrod and asters nearby. The fungus continues to produce spores that re-infect the alternate host until late in the season when spores that infect pine needles are formed, thus completing the rust’s life cycle. The life cycle is completed in one year.
Integrated Pest Management Strategies 1. Live with the disease. Pine needle rusts do very little damage to mature established trees. Young trees or trees grown in a nursery may require more aggressive action. 2. Remove the alternate host. Pine needle rust needs both pine needles and an alternate host of goldenrod or asters to complete its life cycle. Removing these alternate hosts near pines that suffer from the rust disease can break the cycle. 3. Plant resistant species. Replace susceptible pines with Colorado or Norway spruce. White pine is resistant but is not an ideal choice for the St. Louis area.
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Dummer. ゛☀
2017年09月18日
Dummer. ゛☀
Phomopsis blight is a serious disease problem on eastern red cedar in Missouri. The fungal disease, caused by Phomopsis juniperovora, is widespread in this region and can infect arborvitae and cypress as well as juniper. Phomopsis is more of a problem on junipers in landscape plantings because young tissue is most seriously infected. Older plants are seldom killed by Phomopsis, thus it is not a concern in natural stands of juniper.
Symptoms and Diagnosis The first sign of infection is the browning of needle tips. New shoots, in the yellow-green stage, will brown and die in their first summer. Progressive dieback follows, eventually killing an entire branch by girdling the stem. The fungus will progress to the main stem and can infect and girdle stems less than 1/2 inch in diameter. Infected needles turn light green, then reddish-brown, and finally an ashen gray. Life Cycle Phomopsis overwinters on needles and stems of young trees that were infected the previous year. The fungus is most abundant on dead tissue that has become ashen gray in color. Infective spores are dispersed by rain splash. Only seven hours of 100% humidity are needed for infection to occur when temperatures are 75 degrees F.
Integrated Pest Management Strategies 1. Prune infected branches to prevent the spread of the disease. Remove dead tissue as well. The fungus can produce infective spores for up to 2 years in dead parts of infected plants. Prune in late summer when the weather is dry. 2. Plant resistant evergreens. Susceptibility to Phomopsis blight varies considerably among junipers. Ask for resistant stock at your garden or landscape center or consider planting another type of evergreen.
3. Fungicides. Bordeaux mixture, other copper-based fungicides, and mancozeb are labeled for use on Phomopsis. These fungicides can be applied 3–4 times in the spring, at 10–14 day intervals to protect the new growth. They can be used anytime a flush of new growth occurs. Once the new growth matures in midsummer, discontinue further applications.
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