Posted 25 June 2012. PMN Crop News.
Source: University of Illinois at Urbana-Champaign Press Release. www.illinois.edu
Urbana-Champaign, Illinois (June 18, 2012)--Emerald Ash Borer continues to move across Illinois, killing hundreds of ash trees in its path. As we continue our efforts to monitor it here in Illinois, Rhonda Ferree, University of Illinois Extension educator, horticulture, reminds us that there are many other ailments that attack ash.
Several diseases attack ash in Illinois and cause decline. One possible cause of decline is ash yellows. This disease primarily infects white and green ash in the north-central and northeastern parts of the United States. It is a problem in Illinois, but one that is difficult to quantify, because its presence is difficult to confirm. This disease is characterized by a loss of vigor over a period of 2 to 10 years before the tree dies. Symptoms include short growth and tufting of foliage at branch ends. Leaves become pale green to yellow and might develop fall colors prematurely. The tree might defoliate, and the canopy generally appears sparse. Cankers (large dead patches) form on branches and the trunk, causing twigs and branches to die back. Witches'-broom sprouts of growth might appear on some branches but are more common on the trunk near the ground. Cracks in the trunk may appear in this area as well. It is rare for an ash tree to recover from ash yellows.
To complicate matters, Verticillium wilt on ash also results in cankers and dieback and does not cause the typical vascular discoloration of most Verticillium infections. It is difficult and time-consuming to distinguish among ash yellows, Verticillium wilt, and ash decline in Illinois. Diagnosis of these ash problems depends almost entirely on symptoms that could be caused by a variety of problems.
Ash decline is a term that is often used loosely by many diagnosticians to refer to more than one condition. Ash decline usually includes branch tip death, defoliation of enough leaves to give the tree a sparse look, and a slow decline of the tree over a number of years. Trees with ash decline may appear to recover each spring and then decline in July and August.
Trees stressed by these diseases or other factors are more easily attacked by our native borer the lilac ash borer. Native ash borers leave pea-sized round or oval holes in tree trunks or stems, whereas the Emerald Ash Borer (EAB) holes are smaller (1/4 inch) and distinctly "D" shaped.
If you suspect that your ash tree has a problem, Ferree recommends these helpful sources to help you narrow down the problem. University of Illinois Extension has a handy checklist that can be used for identifying the tree and determining if EAB is present. The checklist is available for downloading at www.web.extension.illinois.edu/fmpt. The document is also available from local U of I Extension offices. Due to the volume of contacts, U of I Extension will not conduct site visits. More information on EAB is also available at www.IllinoisEAB.com.
University of Illinois Extension Master Gardener Plant Detectives are armed and ready to help with other ash problem diagnosis.