Maples are one of the most loved shade trees by many homeowners. Unfortunately, the maple is not free of problems. One common problem is wilt in mature trees. the following is information on Maple Wilt.
Maple wilt, also called Verticillium wilt, is a common and serious disease of maples. The destructive soil-borne fungus, Verticillium dahliae, kills many maples each year throughout Delaware.
Norway maples seem especially sensitive to infection by the soilborne fungus Verticillium. Silver, red, sugar, sycamore and Japanese maples are also susceptible. The fungus usually enters a tree by way of its roots and spreads from there through the sapwood into the upper branches. When this happens, one or more large limbs or even the entire crown may begin to die back. Infected limbs will sometimes produce sparse, sickly looking leaves which may later wilt suddenly and die usually in July. Sometimes leaves will have marginal browning or scorch symptoms.
A diseased tree can die within one season, but usually lingers, dying slowly over several years. Survival time depends on the size and vigor of the tree, as well as general weather conditions. Healthy vigorous trees can limit the damage by producing new water conducting vessels free of the fungus. Symptoms can be chronic as well, resulting in reduced growth of trunk, branches, and leaves. Branch dieback can occur as well as premature fall coloration and winter dieback.
Olive-green streaks sometimes can be seen in the sapwood of wilt-infected maples, Usually they will be some distance below the place where the leaves are wilted or scorched. If you cut into the bark at intervals back to where the wilted branch joins the main stem and you do not see any stain, Verticillium is most likely not the cause. If streaking is found, branch samples 4-8 inches long with stain can be collected and submitted to the county extension office for laboratory confirmation.
Once the disease becomes established, it's hard to control. For this reason, it's best to cut down and destroy seriously infected trees. In some cases, though, it may be worth trying to save one, if by pruning out the infected branches, the value of the tree as a landscape plant is not destroyed.
Rescue efforts involve removing dead and dying branches and watering during dry periods. This will sometimes stop the spread of the disease. Feed in the early spring at bud swell with a 10-6-4, 10-10-10 or other high-nitrogen fertilizer. Slow release forms of nitrogen for trees are preferred.
Be sure to keep the tree well watered during dry periods. This is very critical and may be more important than fertilizing in helping the tree to recover.
As with so many plant diseases, it's better to prevent maple wilt than to try to cure it. So keep your maples in healthy, vigorous condition with good annual care. This involves proper feeding, watering, and pruning. Cared for properly, a tree is less likely to become diseased and should thrive for many years.
If Verticillium wilt is diagnosed it is prudent to replant with a plant that is resistant to this disease. A few common examples of plants typically free of this disease include: crabapple, mountain ash, beech, birch, boxwood, dogwood, sweet gum, hawthorn, holly, katsuratree, honeylocust, oak, pear, London planetree and sycamore, rhododendron, willow, and zelkova. The red maple cultivars Armstrong, Autumn Flame, Bowhall, October Glory, Red Sunset, Scarlet and Schlessinger have also been reported as resistant.
Information from Bob Mulrooney, Extension Plant Pathologist, UD.
Showing posts with label maple. Show all posts
Showing posts with label maple. Show all posts
Wednesday, June 4, 2008
Sunday, May 11, 2008
Nursery and Landscape - Anthracnose Diseases in Trees
The cool, wet weather we have had recently will favor the fungi that cause anthracnose diseases in landscape trees. The following is information on several of these anthracnose diseases.
Anthracnose diseases are not all caused by the same fungus. Each host plant has its own anthracnose fungus, so, for example, don't assume that anthracnose of sycamore or grape is a threat to nearby dogwoods. The incidence and severity of anthracnose diseases of landscape trees varies with the season, and this year, symptoms appear to be at moderate levels.
Ash anthracnose. Brown blotches along leaflet edges have been visible for the past week or so on new ash foliage. Many of these infected leaflets will begin to drop soon and carpet the walks and lawns nearby. Ash anthracnose is not normally a threat to ash tree survival, however, and the ash trees will simply put out a new set of leaves. The ash anthracnose fungus is a species of Discula.
Dogwood anthracnose. Caused by the fungus Discula destructiva, dogwood anthracnose is appearing this spring in many flowering dogwoods (Cornus florida). Dogwood anthracnose causes leaf spots, leaf blight, and lower branch dieback and is most commonly observed in forested regions where native understory dogwood trees are threatened. This spring, anthracnose is also present in landscape trees, especially those growing in shaded locations.
Maple anthracnose. Symptoms can range from leaf spots to shoot blight and shoot cankers. Maple anthracnose may be caused by Discula sp. or by Kabatiella apocrypta. There is considerable variation in maple susceptibility to anthracnose. In some cases, sugar maple leaf spotting may be heavy on one tree while the adjacent tree is barely affected.
Oak anthracnose. This disease is less common and is caused by the fungus Apiognomonia quercina.
Sycamore anthracnose. Anthracnose symptoms on infected green, expanding leaves, look for irregular dark, necrotic blotching centered along the leaf veins or leaf edges. These dark blotches may turn a tan color as the diseased areas of the leaves dry out. In the same trees, tips of young shoots with newly expanding leaves are wilting and dying because of twig or shoot infection. With continued rainy weather, the disease should continue to spread in the foliage. Symptoms are not as severe as we see some years when trees are heavily defoliated by now. As the weather gets warmer and drier, sycamores normally put out new, healthy foliage. However, the legacy of crooked branches (because lateral shoots take over when terminals are killed by anthracnose) and multiple shoots arising from the base of a killed branch may still be visible many years later. Sycamore anthracnose is caused by the fungus Apiognomonia veneta, and the fungus attacks both sycamore and London plane.
Delaware growers and gardeners should know how to grow and maintain healthy landscape trees. For most trees, anthracnose disease is not lethal, but it can be for dogwoods. Good growing practices are important in reducing the effects of anthracnose and in preventing loss of dogwoods from anthracnose. Consider the following:
Rake up and compost fallen leaves. Leaves can be a source of inoculum.
Prune out and destroy dead twigs and branches, because for many of the anthracnose fungi, branches harbor fungal inoculum. Although it is difficult to prune large trees, small trees are at greater risk, so prune out dead twigs and branches from them. For dogwoods, pruning out dead branches and water sprouts is especially important where anthracnose might be a threat.
Avoid unnecessary wounding and avoid construction or other activities which could injure the roots or the branches.
Provide mulch as needed. Maintain a 2-3 inch layer of mulch over the root zone of the tree (but not against the trunk) to help maintain soil moisture and to protect trees from lawnmower injury.
Protect trees from drought by watering at least once a week during dry periods. Do not use overhead sprinklers for watering; wet foliage favors infection.
Do not transplant dogwood trees from the wild. Purchase healthy trees from a reputable nursery.
Anthracnose is favored by a moist environment. Select a planting site with a sunny eastern exposure to promote rapid foliage drying early in the day.
Diagnose and treat insect and disease problems appropriately.
Plant disease resistant dogwoods such as C. florida 'Appalachian Spring' or oriental dogwoods (Cornus kousa) for high risk sites such as those with heavy shade and nearby diseased trees.
Although most anthracnose diseases can be controlled using fungicides, the attempt is usually more costly than the benefit. Dogwoods which are threatened by anthracnose may benefit from early spring fungicide applications.
Adapted for Delaware from "ANTHRACNOSE DISEASE SYMPTOMS APPEARING IN LANDSCAPE TREES" By John Hartman in the May 22, 2006 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.
Anthracnose diseases are not all caused by the same fungus. Each host plant has its own anthracnose fungus, so, for example, don't assume that anthracnose of sycamore or grape is a threat to nearby dogwoods. The incidence and severity of anthracnose diseases of landscape trees varies with the season, and this year, symptoms appear to be at moderate levels.
Ash anthracnose. Brown blotches along leaflet edges have been visible for the past week or so on new ash foliage. Many of these infected leaflets will begin to drop soon and carpet the walks and lawns nearby. Ash anthracnose is not normally a threat to ash tree survival, however, and the ash trees will simply put out a new set of leaves. The ash anthracnose fungus is a species of Discula.
Dogwood anthracnose. Caused by the fungus Discula destructiva, dogwood anthracnose is appearing this spring in many flowering dogwoods (Cornus florida). Dogwood anthracnose causes leaf spots, leaf blight, and lower branch dieback and is most commonly observed in forested regions where native understory dogwood trees are threatened. This spring, anthracnose is also present in landscape trees, especially those growing in shaded locations.
Maple anthracnose. Symptoms can range from leaf spots to shoot blight and shoot cankers. Maple anthracnose may be caused by Discula sp. or by Kabatiella apocrypta. There is considerable variation in maple susceptibility to anthracnose. In some cases, sugar maple leaf spotting may be heavy on one tree while the adjacent tree is barely affected.
Oak anthracnose. This disease is less common and is caused by the fungus Apiognomonia quercina.
Sycamore anthracnose. Anthracnose symptoms on infected green, expanding leaves, look for irregular dark, necrotic blotching centered along the leaf veins or leaf edges. These dark blotches may turn a tan color as the diseased areas of the leaves dry out. In the same trees, tips of young shoots with newly expanding leaves are wilting and dying because of twig or shoot infection. With continued rainy weather, the disease should continue to spread in the foliage. Symptoms are not as severe as we see some years when trees are heavily defoliated by now. As the weather gets warmer and drier, sycamores normally put out new, healthy foliage. However, the legacy of crooked branches (because lateral shoots take over when terminals are killed by anthracnose) and multiple shoots arising from the base of a killed branch may still be visible many years later. Sycamore anthracnose is caused by the fungus Apiognomonia veneta, and the fungus attacks both sycamore and London plane.
Delaware growers and gardeners should know how to grow and maintain healthy landscape trees. For most trees, anthracnose disease is not lethal, but it can be for dogwoods. Good growing practices are important in reducing the effects of anthracnose and in preventing loss of dogwoods from anthracnose. Consider the following:
Rake up and compost fallen leaves. Leaves can be a source of inoculum.
Prune out and destroy dead twigs and branches, because for many of the anthracnose fungi, branches harbor fungal inoculum. Although it is difficult to prune large trees, small trees are at greater risk, so prune out dead twigs and branches from them. For dogwoods, pruning out dead branches and water sprouts is especially important where anthracnose might be a threat.
Avoid unnecessary wounding and avoid construction or other activities which could injure the roots or the branches.
Provide mulch as needed. Maintain a 2-3 inch layer of mulch over the root zone of the tree (but not against the trunk) to help maintain soil moisture and to protect trees from lawnmower injury.
Protect trees from drought by watering at least once a week during dry periods. Do not use overhead sprinklers for watering; wet foliage favors infection.
Do not transplant dogwood trees from the wild. Purchase healthy trees from a reputable nursery.
Anthracnose is favored by a moist environment. Select a planting site with a sunny eastern exposure to promote rapid foliage drying early in the day.
Diagnose and treat insect and disease problems appropriately.
Plant disease resistant dogwoods such as C. florida 'Appalachian Spring' or oriental dogwoods (Cornus kousa) for high risk sites such as those with heavy shade and nearby diseased trees.
Although most anthracnose diseases can be controlled using fungicides, the attempt is usually more costly than the benefit. Dogwoods which are threatened by anthracnose may benefit from early spring fungicide applications.
Adapted for Delaware from "ANTHRACNOSE DISEASE SYMPTOMS APPEARING IN LANDSCAPE TREES" By John Hartman in the May 22, 2006 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.
Thursday, September 6, 2007
Ornamentals Hotline Disease Pictures for Issue 24, September 7, 2007
Cercospora on SourwoodPhoto by Bob Mulrooney, University of Delaware
Walnut AnthracnosePhoto from the University of Minnesota Yard and Garden Line News
Tar Spot on MaplePhoto by Steven Katovich, USDA Forest Service, Bugwood.org
Subscribe to:
Posts (Atom)
