Camperdown Elm infestation

Asked October 22, 2017, 8:34 PM EDT

I have a Camperdowm Elm that is about 7 years old. It is being chewed terribly by something. A Dwarf Nandina is planted next to it and the Nandina is also being chewed. This is the second year this has happened. I have tried Seven in the past but don’t like to use such harsh chemicals. Can you tell what is attacking the tree and what I should to to save my beautiful tree? Thanks in advance....

Marion County Oregon trees and shrubs diagnosis of plant problems horticulture

1 Response

Thanks for contacting Ask an Expert. I think we can help out with your Camperdown elm.

The Elm Leaf Beetle appears to be the culprit. It can be devastating on many elms, and its damage matches some of the damage in the photos you sent. Some other photos can be found here and attached for comparison.

The first order of business is to keep the tree healthy, through supplemental watering in hot, summer weather and a dose of fertilizer, as growth starts in spring. When needed, prune in later winter (January).

The elm leaf beetles overwinter in protected areas around the yard and lay eggs in spring on the leaves. Both the adult beetles and the juvenile grubs do damage—chewing holes and skeletonizing the leaves. The first generation begins its dirty work in May and June, with a second generation following later in the summer.

Keep your eye out for the first signs of attack. Younger grubs are easier to control. Suggested sprays are acephate, azadirachtin, bifenthrin, and cyfluthrin. Check with your local nursery or garden center for a product containing one of these active ingredients. Be sure to read the label and follow all the directions and precautions.

As summer progresses, watch out for that second generation of elm leaf beetles, and spray again, if needed.

As far as the nandina—I do not see any references that lead me to believe that the elm leaf beetle will attack those plants, too. However, there are several caterpillars that feed on a wide variety of plants and may be responsible. Maintain your watch on your tree to discover other invaders.

For further information, you can consult your Marion County Master Gardeners at 503-373-3770 or take actual samples in to them at 1320 Capitol St. NE.