Chemical insecticides are only effective until the target pest develops a resistance to that chemical. Then it becomes necessary to alternate harmful substances to control an insect population that continually gets worse because of lack of competition and natural predators, due to high concentrations of chemicals. The major rose pests that we encounter here in Southern California can be controlled by establishing populations of two beneficial insects, plus periodic treatments with a bacterial and a tree sap extract. The two beneficial insects are the green lacewing and trichogramma wasps. These two insects will guard your roses against everything from aphids to some scales and spider mites.
Lacewings are very active and voracious feeders.
Their target prey are aphids, mealybugs, some species of whitefly, juvenile scale insects, and some spider mites. The tiny trichogramma wasp is a parasite of caterpillars some species of bud worm. They will also antagonize a number of other butterfly and moth species. BT is a paralyzing bacteria that affects many species of worm and caterpillar including the leaf skeletonizer worm. By paralyzing the stomach of its host, this bacteria is very useful against its target pests.