My knockout roses are full of Japanese Beetles. Help!

Asked July 24, 2014, 4:11 PM EDT

Japanese beetles are on my "knockout" roses and appear to be eating the leaves. What can I do to get rid of them other than "hand pick them off." Thank you.

Charles County Maryland

1 Response

You are not alone. The knock-out roses are taking a beating this year.
In many cases there are two culprits, both japanese beetles (which like the leaves but decimate the flowers) and the rose slug, which is the larvae of a sawfly, which looks like a small bright green caterpillar.
'Hand-picking' is a bit of a misnomer, in that you don't really have to touch them. We recommend putting an inch or two of soapy water in a pail/container (plastic carry-out containers work) and hold it just under them. When you bump the leaf they tend to fall straight down and cannot escape the water. This method puts a pretty good dent in the populations without chemical inputs.
You can also spray (not on a hot day, which can damage your plants) neem oil on them.
There is a new insecticide called spinosad (this is the active ingredient) which is labeled to work on both japanese beetles and the rose slug. (it performs better on the slugs) as well.