Knowledgebase
Rose bushes with holes in leaves #754486
Asked June 07, 2021, 11:57 AM EDT
Montgomery County Maryland
Expert Response
The white window paning (etched surfaces) or small holes on the foliage looks like rose slug damage. These are insect larvae, not slugs, and are in the group called sawflies. They are easy to miss, small and wormy looking and often can be found beneath the leaves. Look under the leaves. It is possible the damage may have been done.
Here is our page on them and how to best control: https://extension.umd.edu/resource/roseslug-sawflies-shrubs
https://extension.umd.edu/resource/common-problems-roses
Hand picking/squishing works and the most environmentally-friendly approach would be to try to blast the leaf undersides with a harsh jet of water from a hose nozzle. Sawfly larvae can't get back onto the plant after being dislodged like this.
Otherwise, low-impact insecticides like a summer rate of horticultural oil or spinosad (an active ingredient in several products) will help control them while having minimal or no impact on beneficial insects.
Spray upper and lower leaf surfaces. Follow label directions about how often repeat treatments can be / need to be made. Some rose slug species have more than one generation per year, so control efforts may need to be made more than once if you see damage continuing.
Marian