Knowledgebase
(insect ID) Sawfly caterpillars on Knock out Roses #872787
Asked June 12, 2024, 11:53 AM EDT
We have lots of knockout roses at the entrance to our new subdivision. One bed of them has lots of damage from what appear to be sawfly caterpillars. What should we do to manage this problem?
Oakland County Michigan
Expert Response
Hello Greg,
This appears to be imported rose sawfly larvae, Arge ochropus.
They are not caterpillars, so insecticides like bt will not control them.
https://extension.uga.edu/programs-services/landscape-pest-management/Nursery-pests/sawflies.html
The following is from the Royal Horticultural Society. I don’t know if all the mentioned insecticides are available here but, if you can avoid insecticides on the flowers or when bees and other pollinators are present, that would be best. See their suggestions on how to do that.
https://www.rhs.org.uk/biodiversity/large-rose-sawfly
INaturalist has pictures, including what the egg scar looks like. By destroying eggs, as suggested by RHS, you can reduce the local population.
https://www.inaturalist.org/taxa/447507-Arge-ochropus/browse_photos
