Rhododendron Borer – Identification
Q: We noticed wilted leaves on some of our rhododendron this morning. When my husband removed the branch it had the dreaded hole in it. Some of the holes go all the way into the ground. Do we need to remove the whole plant or can we treat the plant and save the healthy portions? What can we do to protect the healthy rhododendron around the sick ones?
We live in Lumpkin County.
A: Rhododendron borer is the larvae of a clear-winged moth which lays its eggs on the bark of a rhododendron. Larvae from the eggs tunnel into the rhodie branch and feed on the sapwood.
The first symptom is usually wilted leaves on a single branch.
The hollow stem is the best way to conclusively identify the pests.
Control is begun by pruning out affected branches as soon as you see them. Afterward, spray nearby plants (especially the small limbs and branches) with a product that contains permethrin three times in May and June at 10 day intervals.