Any Ash is Good Ash?

Photo K. Arrell

When I was learning to identify trees I had an instructor who was great at coming up with catch phrases to remember tree I.D. I still remember his comments on ash trees which I have used as the title for this article. Ash trees have long been prized for its adaptability, survivability and versatility. Lately it has also been in the news for its susceptibility.

Anthracnose is a common fungal disease of both green and white ashes. It occurs seasonally in spring and can result in the defoliation of the lower third of the tree. Buds, twigs, and leaves can become infected. Typically leaves will exhibit irregular or sickle shaped distortions as well as blotchy lesions.Severely impacted leaves may be shed from the tree and should be removed from the area as they are a source of reinfection. On occasion the disease may attack the petiole, or leaf stem resulting in extensive defoliation. Cultural practices general are effective in reducing the extent of the disease and preventative fungicides applied at bud break should only be used as a last resort.

Ash yellows is a vascular disease of ash trees is caused by a phytoplasm, a type of microbe. Both white and green ash are affected as well as a dozen other ash species. Susceptibility varies among species and individual trees with the most severely impacted trees dying within months. More resistant trees may last for years with various symptoms. Stunted sickly growth, and the presence of witches brooms, thick broom like growths, are the main symptoms. This disease is spread by insects that feed on leaves by sucking sap. Maintaining the vigor of less severely impacted trees may prolong their lives, heavily impacted trees should be removed.

Ash plant bug is a native pest that does damage to ash leaves by inserting its sap sucking mouth parts into the upper surface of leaves. This action causes yellow stippled areas that may coalesce into large yellow patches. The feeding may cause browning and distortion of foliage that can be confused with anthracnose. One key way to differentiate between the two is to look at the underside of the effected leaves and you may find black spots, waste from the plant bugs called frass. These insects have two generations per year and may cause extensive damage. They are easily controlled by a number of insecticides applied early in the season , including horticultural soaps and oils

Emerald ash borers are a newer introduced threat to ash trees. The original infestation was probably the result of green wood in the form of packing materials that originated in the beetles home range, Eastern Asia. The adults themselves feed on the leaves of ash trees but cause little damage. In late June to early July, they lay their eggs on the bark of ash trees usually in cracks crevices and fissures. The eggs hatch, burrow into the inner bark, the cambium layer, and begin to chew their way though the vascular cambium in up to foot long serpentine feeding galleries. The tree is unable to survive the injury to its vascular system, starts to wilt and die back and will last only one to three years once infested. Avoid transporting ash nursery stock or fire wood.

I.S.A.Certified Arborists are knowledgeable in identifying ash disease and insect problems. Take the time to consult with your Certified Arborist if you suspect your ash tree has problems.