Rose failure/insect damage

Asked May 22, 2017, 11:39 AM EDT

For the past few years my roses have struggled to bloom-even the Knockouts. Many of my roses are from David Austin collections.This change in flowering is despite no significant change in care (proper pruning, feeding & even soil improvement.) Even during the expected spring flush many of my plants will have shriveled, distorted buds that never fully develop to flower. The foliage looks healthy & normal, just very few & strange looking buds. I spray with hort oil early in the season & fertilize with Espoma organic rose food. I have been trying to figure out what's going on & recently read an article about rose midges & it seems to be a possibility, looking at the pictures shown, as well as finding small bore holes on bud stems of some of my roses. If so, how do I treat this? Or are there other pests that could cause these symptoms? Thank you for you help. Durant

Anne Arundel County Maryland

1 Response

Rose Midge can be a vexing problem.
The larvae infest the newly formed bud and cause the bud not to develop, turn brown, wither and fall off thus preventing new flowers. It can affect all kinds of roses, including Knock Outs. An infestation of rose midge can prevent flowering.
According to rose experts, control consists of removing mulch around rose shrubs in late winter, which removes some of the pupating rose midges. Putting fresh mulch on in early spring buries deeper any remaining midges. (It may be too late tor this to be effective now if you are already seeing affected buds.)
Physical removal can also help with control. Monitor weekly for infested shoots throughout the growing season and prune off infested shoots when possible. There are up to 35 larvae in one shoot. Black shoots are an indication that the larvae are gone. Applications of spinosad applied every 10 days will help to control the insect.