The new growth on my honeylocust tree is deformed. What causes this?
Several insects and mites feed on honeylocust trees and can cause conspicuous injuries. Heavy infestations can reduce tree growth rate and vigor but rarely cause permanent injury. The culprit is usually the larvae of the honeylocust podgall midge, which cause the infested leaflets to curl and thicken, forming small “pod galls” instead of expanding normally. This pest has multiple annual generations, of which the most damaging is the earliest one, occurring from the time of first growth through mid-summer. Chemical controls have been only moderately successful. These include pyrethroids, Carbaryl, and Mavrik, which should be applied to coincide with the first flush of new growth and repeated every three or four weeks until mid-summer. (NOTE: Do not use dimethoate (Cygon) which is extremely toxic to honeylocust.) For information on other pests and diseases affecting the honeylocust, see CSU Fact Sheets 5.571 and 2.939.
