Little Green Worms on Roses & Stems

Description

• Roseslugs include the European roseslug sawfly, the curled roseslug sawfly and the bristly roseslug sawfly. All three species have green bodies and orange heads. The bristly roseslug is easily identified by the bristly hairs that cover it, and the curled roseslug curls its body when resting. Roseslugs grow to be about 3/4 inch long. To distinguish roseslugs from caterpillars, count the number of prolegs, or fleshy structures that are found behind the front three pairs of legs. Caterpillars have fewer than five and sawflies have five or more. Some roseslugs produce a slime that covers their bodies like slugs, but they aren’t related to them.

Damage

• Roseslugs can be found on the undersides of leaves where they eat most of the tissue between the veins, giving leaves a skeletonized look. Older bristly and curled roseslugs chew holes in the leaves instead of skeletonizing them. The damage they cause is usually cosmetic, although heavy attacks can weaken plants and leave them susceptible to disease. Damaged leaves turn brown and die, and heavily infested bushes look burned.

Nonchemical Control

• Roseslugs have several natural enemies including parasitic wasps and beetles that help reduce their population. If natural predators aren’t enough, you have some nonchemical ways to help control them. Spray rosebushes with a strong stream of water to remove worms from the leaves. Spray early in the day to give leaves a chance to dry. This reduces their chances of becoming infected with a fungus. You can also pick roseslugs off by hand.

Chemical Control

• Insecticides kill beneficial predators as well as roseslugs so, if you need to use an insecticide, it’s best to use the least toxic one possible. Horticultural oils, neem oil and insecticidal soap are good choices because they don’t leave a toxic residue behind. Only use insecticides when you can actually see that roseslugs are present. They’re not meant to be used as a preventive treatment. Bacillus thuringiensis, or Bt, a biological insecticide that’s commonly used against caterpillars, doesn’t work against slugworms.