Hi. i”m hoping you can help me. we planted columnar red oaks last year and noticed holes in both trees recently. I can’t see any sign of insects on the leaves – any ideas what I should do?
thanks in advance.
Thank you for contacting the Toronto Master gardeners with your inquiry reqarding your red oaks.
From your photograph it appears that in the holes your red oaks could be the result of Agromyzid midge. The midge adults would have caused the holes back when the leaves were still folded up inside the bud, resulting in a “snowflake” like pattern of holes once the leaves expanded. Most midge larvae emerge during autumn, however some species of midges will appear in the spring. The larvae are white, yellow or bright orange, depending on the species, and look like tiny maggots. Eventually, the larvae drop to the ground, dig in and pupate over winter. In spring, a new hatch of midges appear and the cycle begins again. The larvae survive on plant juices while encased inside the gall, but do not consume enough liquid to harm the tree.