The key is to try to conserve rust mites, which are alternative prey for the predatory mites and cause little damage to the tree. He cautioned that sulfur is toxic to rust mites. Predatory mites may starve if their food supply is destroyed. Biological control of grape mealybug by parasites such as the wasp Acerophagus notativentris and leucopis flies, has not proven very successful, said Dunley, who has been studying potential predators. The ladybeetle is not well synchronized with the mealybug, but lacewings and earwigs have shown some promise.
Earwigs tend to inhabit hidden places where mealybugs are often found.
In tests, Dunley has been able to encourage the build-up of earwigs by wrapping burlap around the trunks of trees. While they may provide some control, they will not be the total answer and can damage fruit themselves, he warned. Green lacewings can control mealybug fairly well and can be bought commercially from insectaries. Releases of larvae have been more effective than egg releases, but Dunley said larvae are much more expensive.