Rhododendrons are a major landscape plant in the south. We start to see them burst into flower in the spring and they are magnificent. But that is also the time to prevent rhododendron borer damage. The damage from this insect won’t be evident until the fall when small wilted branches start showing up. At this point the only thing that can be done is to prune out the wilted and dead parts and burn them. Once borers enter the plant, chemical control is useless.

The adult rhododendron borer resembles a wasp and lays eggs on the bark of the rhododendron. These eggs hatch in to small caterpillars in early summer and by fall they have tunneled in to the trunks, branches and limbs of the plant.  Sprays containing permethrin will protect the wood from the larvae. Thoroughly spray the bark 3 times in May and June at 10-14 day intervals. Some readily available brands are Bonide Total Pest Control Outdoor Concentrate and Hi-Yield Indoor/Outdoor Broad Use Insecticide Concentrate.

Treat your rhododendrons in May and June to prevent damage from this destructive pest!