Knock out roses have an issue

Asked April 27, 2019, 1:20 PM EDT

Representatives from Catonsville public library suggested we reach out to you for assistance. The knockout roses have something destroying them. Please help and advise what to do to combat the problem. We have tried using Sevin and that did not help. Thanks in advance

Baltimore County Maryland

1 Response

The holes on the leaves are caused by rose slug sawfly larvae. Look on the undersides of the leaves for the young larvae. If the infestation is light, pick off and destroy the larvae by hand. To control heavy infestations, use horticultural oil or spray with spinosad. Target the undersides of the leaves. See our website for more information