Apple leaf (curling) midge, Dasineura mali (Kieffer), Diptera: Cecidomyiidae has caused some damage this season in NY and New England. In New York scouts reported injured leaves observed during the pre-bloom period, caused by the 1st generation of this pest, and this week in Massachusetts caused by the 2nd generation of the midge. Its distribution includes eastern Canada, NY, and New England states. As there are two or three generations produced each season the leaf curling can be seen in infested orchards from petal fall through harvest.
Larvae feeding causes foliar damage, attacking leaves and flowers of apple trees and producing a red curled leaf edge. Most of the injury occurs at the shoot tip. In newly planted trees, midge feeding will result in reduced extension growth.
The larvae, 2-3 mm in length, are a yellow-white maggot with a reddish tinge in color. No head capsule is apparent as in leafroller larvae. They will spend most of their life within a rolled leaf. Once mature they drop to the ground to pupate. Infestations appear as tightly rolled leaves developing as the early instar larva feed. Leaves then turn brown, dry and drop from the tree.
The adult of the first generation is a very small dark brown fly about 1.5-2.5 mm in length, emerge in May, mate and females begin to lay eggs on developing leaves. The eggs hatch in 2-10 days, with larvae feeding on leaves upon emergence.
This tends to be a sporatic pest, and in mature trees is of little consequence. And as such there are no thresholds for leafcurling midge. However, in areas of high pressure, especially in nurseries and orchards of newly planted trees, leaf injury may result in reduced growth of extension shoots in which case control measures should be taken. I am not aware of insecticides with Apple Leaf Curl Midge on the label. The use of the systemic insecticide Movento (plus penetrant ) and the neonicotinoid insecticides (Actara, Assail, Calypso, Admire Pro), which have translaminar characteristics, will likely reduce apple leaf midge larva feeding when these materials are used against wooly apple aphid, San Jose Scale, leafhopper and rosy apple aphid.