Adults emerge in early May. Eggs will hatch a few days after being laid within the leaves. At the end of May, larvae will leave their mines and pupate within the soil. Overwintering will also take place in the soil. Hawthorne leafminers only have one generation a year.
Controls should be applied around the first of May. Monitor trees for adult activity as well as egg laying scars on the leaves.Chemical treatment can be applied in the fall to control hawthorn leaf miner in spring. The directions are quite explicit on the label for trees and shrubs. Please note that the treatment can also control lacebugs, leafhoppers and aphids.
(Credits and notes regarding photos: Bottom row of photos taken on 10 May 2001 by Mary Welch-Keesey, Consumer Horticulture Specialist, Purdue University. The leaf was from C. crus-galli at White River Gardens in Indianapolis and there were many damaged leaves. Most of the larvae had already dropped to the ground at that point.)
Click on the small image to view a larger image.
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Last updated: 16 May 2001/tlm.
The Plant & Pest Diagnostic Laboratory at Purdue University.