Ash Yellows Disease
We have a Bergeson ash in our yard in Halstad MN that has been dying back and yellowing for a few years. Is ash yellows disease found in our area? If our ash tree is diseased, is there any cure? If the tree has to be removed, will the disease remain in the soil and affect a new tree planted in the same spot?
Ash trees in MN are declining for a variety of reasons. Environmental stress, stem girdling root, verticilium wilt, and ostershell scales have symptoms that are similar ash yellows phytoplasma. http://www.extension.umn.edu/garden/diagnose/plant/deciduous/ash/leavesyellow.html A tree infected with the ash yellows phytoplasma may express symptoms such as reduced shoot growth, lack of apical dominance (branch angle), dieback, bright yellow chlorotic foliage, and witches’-brooms. Chlorosis is a term often used to describe a plant condition identified by yellowing of the leaf surface where the veins remain a darker green color. Witches’-brooms are clumped simple leaves on shortened shoots creating a “broom like” appearance. The Iowa forestry article will help you determine why your tree is declining. https://www.extension.iastate.edu/forestry/publications/PDF_files/F-373.pdf http://hort.uwex.edu/articles/ash-yellows If you suspect your tree has ash yellows (yellow foliage and witches broom) it should be tested for the disease. http://pdc.umn.edu/ There is no treatment available to ash yellows. If it tests positive it should be removed immediately to prevent spread of the ash yellows phytoplasma to other trees in your area. Leafhoppers are the primary means by which this pathogen is moved from tree to tree. It does not remain in the wood or soil. It is best to avoid planting new ash trees because of Emerald ash borer.