University of Maryland Extension

Locust Leafminer - Trees

locust leaf miner and damage
Locust leafminer adult and damage

The locust leafminer (Odontota dorsalis) is a serious pest of black locust (Robinia pseudoacacia). Black locust is the favorite host for the adult beetles but will occasionally attack apple, birch, beech, cherry, elm, oak, and hawthorn. Heavily infested trees appear scorched or burned. These trees will drop their leaves and will refoliate during the summer.

The adult locust leafminer is a small beetle, about 6mm long. The adult beetles overwinter in bark crevices, under litter, etc. The adults emerge in the spring about the same time that the black locusts are leafing out. The adults chew holes in the leaves and skeletonize the lower leaf surfaces. Eggs on the lower leaf surfaces, in groups of 3-5. Upon hatching, the larvae from a given group of eggs bore into a leaf and feed in a common mine eventually separating and feeding in individual mines which form irregular blotches. The larvae tend to prefer the terminal portion of the leaves and pupate in the mines. Adults emerge and repeat the cycle again.

locust leafminer damageOutbreaks of the locust leafminer occur practically every year, and thousands of black locusts turn brown and are defoliated. Trees that are defoliated seldom die. However, if the damage occurs during a year of drought, or other poor growing conditions, the trees may be killed. If the trees grow two sets of leaves in one growing season, the combined feeding of larvae and adults may destroy both sets. If this double defoliation occurs several years in a row, the tree may die.

 

Management

To help trees better withstand the effects of defoliation, provide adequate water during the summer and fertilize occasionally. Healthy, vigorous trees are better able to withstand the effects of defoliation that are stressed trees.

Additional Resource

(PDF) HG3 Locust Leafminer

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