Twig girdler beetle on KnockOut Roses ?

Asked September 24, 2018, 7:37 PM EDT

I noticed a dead branch on my knock out rose bush that looked like a beaver chewed the stem. I removed the stem (this was last Friday). Then on Saturday I noticed two more stems with beaver like damage (see photo). I read the UMD-Ext HGIC article on Twig Girdlers and Twig Pruners -- could this be what did the damage despite this happening to my rose bush and not the typically impacted trees? I cut and removed the branches below the beaver-cut -- should I put them in a bag for the garbage? Since it is a rose bush that i normally cut back in the winter i am not too worried -- unless you tell me i should be????

St. Mary's County Maryland shrubs european hornets pest insects and mites twig girdlers twig pruners rose shrub with girdling

1 Response

It could be a girdler, though the gnawing of a twig girdler is ultimately more tapered (think of how a beaver in a cartoon gnaws the wood into two convex points, like an hourglass shape.)

The twig pruner makes a cup-shaped concave cut, and that doesn't look like yours.

It also could be the work of an European hornet. If you see hornets flying around the shrub, they may be the culprits, though they prefer to strip bark from lilacs. Here is information about them: https://extension.umd.edu/hgic/topics/european-hornets

Since we can't say for sure, and as you said you'll be pruning your roses anyway, we'd recommend that you prune off below the girdled parts, bag, and dispose, just in case it is twig girdlers.

ECN