Troubleshooting
White Ash problems — and how to fix them
White Ash (Fraxinus americana) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Emerald Ash Borer (Agrilus planipennis)
This invasive Asian beetle is devastating North American ash trees. Larvae feed on the cambium, girdling the tree. Symptoms: canopy dieback from the top down, D-shaped exit holes, bark splitting, and epicormic shoots at the base. Biological controls and systemic insecticides (emamectin benzoate, imidacloprid) can protect individual high-value trees. In heavily infested areas, consult an arborist about management or replacement with resistant alternatives.
Ash Yellows (Candidatus Phytoplasma fraxini)
A phytoplasma disease causing stunted foliage, witches' broom growth, premature autumn colour, and general decline. Spread by leafhoppers. No cure; infected trees should be removed and destroyed to reduce spread. Select healthy, certified nursery stock.
Anthracnose (Discula fraxinea)
Causes brown scorching and blotching of leaflets along midribs in cool, wet springs. Premature defoliation can occur in severe years. Trees typically reflush and recover. Rake and destroy fallen leaves; prune out any dead wood. Fungicide sprays at bud break can help in persistent cases.
Prevent white ash problems before they start
Most white ash issues are care-mismatch, not bad luck. Dial in the basics:
White Ash problems — FAQ
Why is my white ash emerald ash borer (agrilus planipennis)?
This invasive Asian beetle is devastating North American ash trees. Larvae feed on the cambium, girdling the tree. Symptoms: canopy dieback from the top down, D-shaped exit holes, bark splitting, and epicormic shoots at the base. Biological controls and systemic insecticides (emamectin benzoate, imidacloprid) can protect individual high-value trees. In heavily infested areas, consult an arborist about management or replacement with resistant alternatives.
Why is my white ash ash yellows (candidatus phytoplasma fraxini)?
A phytoplasma disease causing stunted foliage, witches' broom growth, premature autumn colour, and general decline. Spread by leafhoppers. No cure; infected trees should be removed and destroyed to reduce spread. Select healthy, certified nursery stock.
Why is my white ash anthracnose (discula fraxinea)?
Causes brown scorching and blotching of leaflets along midribs in cool, wet springs. Premature defoliation can occur in severe years. Trees typically reflush and recover. Rake and destroy fallen leaves; prune out any dead wood. Fungicide sprays at bud break can help in persistent cases.