A new adult emerges several weeks later. In northern Illinois as many as four generations per year may occur. The best way to reduce birch leaf miner damage is to watch for the first mines in May and then treat. Read and follow label directions. Both types are slender, flattened, quick moving insects that feed on the sap of leaves and stems.
Immature insects are similar in color, but smaller.
Ash plant bugs cause tiny light spots on leaves and small dark black spots on the underside of the leaf. Honeylocust plant bugs feed on expanding leaflets, causing distortion and twisting. These leaflets usually stay on the tree, marring the appearance for the growing season, but not harming the tree. Heavy infestations will cause leaves to drop from the tree during June but damaged trees will refoliate. Treatment for plant bugs is rarely needed.