Tree Diseases


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Tree Diseases

  1. 1. Urban Forestry Plant: Elm Tree Urban Forestry
  2. 2. Urban forestry <ul><li>The care and management of urban forests, (tree populations in urban settings) for the purpose of improving the urban environment </li></ul><ul><li>Most urban trees are non-native and selected for particular aesthetic qualities </li></ul>
  3. 3. Elm Tree <ul><li>The American or White elm is the largest species of elm.  Usually over 100ft high. </li></ul><ul><li>Due to its graceful form and size, it was an extremely popular urban tree before the spread of Dutch elm disease.  </li></ul><ul><li>Once found mostly in eastern North America, remaining populations of mature American elms are concentrated in the American Midwest and Canadian Prairies.    </li></ul>
  4. 4. Dutch Elm Disease <ul><li>Dutch elm disease (or DED) is caused by a fungus. After the disease is contracted, spores rapidly reproduce and spread toxins throughout the tree. </li></ul><ul><li>Fungus is spread by the elm beetle </li></ul><ul><li>The fungus blocks the vascular system of the tree preventing water and minerals from reaching the branches and leaves. </li></ul><ul><li>The leaves wilt and eventually the tree dies. </li></ul><ul><li>In Washington, DC, the disease has killed over 25,000 elms since 1950 with only 8,200 elms presently remaining on city streets. </li></ul>
  5. 5. Combating Elm Disease <ul><li>Because Elms are such an important urban species, much $ and effort goes into keeping them alive </li></ul><ul><li>Fungicides are injected into the root flare </li></ul><ul><li>Disease resistant elms are often planted as replacement trees. Washington DC tries to maintain the annual DED loss at below 2% of the remaining elm population. </li></ul>
  6. 6. Anthracnose <ul><li>Fungus that attacks hardwood shade trees </li></ul><ul><li>Kills the buds, damages the leaves and causes premature leaf drop </li></ul><ul><li>Over time weakens the tree and makes it susceptible to borers and other pest damage </li></ul><ul><li>Fungus overwinters in leaves on the ground. </li></ul><ul><li>Remove all fallen leaves and dispose of them </li></ul><ul><li>Treat by using fungicides </li></ul><ul><li>Tree on right was treated </li></ul>
  7. 7. Emerald Ash Borer <ul><li>Asian Beetle that bores under the bark of ash trees & lays eggs. </li></ul><ul><li>The larva hatch and eat the cambium layer of the tree </li></ul><ul><li>Has killed millions of trees around the great lakes and is moving south into WV, PA, & VA. </li></ul><ul><li>Treatment is expensive and requires trained applicators. </li></ul>
  8. 8. Cankers <ul><li>Caused by fungus penetration of the bark </li></ul><ul><li>Treatment – pruning below affected area </li></ul><ul><li>Sterilize tools afterwards so as not to spread the disease. </li></ul>
  9. 9. Rust Diseases <ul><li>Cedar Apple Rust is biggest problem </li></ul><ul><li>Affects crab apple trees and junipers </li></ul><ul><li>Lives part of life cycle on each tree </li></ul><ul><li>Destroy galls before April when they spread by spores </li></ul><ul><li>Don’t grow cedars and apples close together </li></ul><ul><li>Select resistant plants </li></ul>
  10. 10. Galls <ul><li>Growths that form on the leaves or stems of plants </li></ul><ul><li>Can be caused by insects or viruses </li></ul><ul><li>Rarely affect the overall health of a tree </li></ul><ul><li>No treatment is required </li></ul>