Boxwood Leaf Miner

Symptoms: The larvae of this fly feed on the tissue between the outer surfaces of the leaves. This feeding results in blotch shaped mines in the boxwood leaves. The infested leaves appear blistered from late summer through the following spring. New leaves do not show signs of mining until late summer when the larvae are larger. By, fall, or in early spring, premature leaf-drop may result from heavy infestation.

What causes damage: Adult leaf miners emerge in late April or early May, depending on the weather. The adults are small (3mm), orange, mosquito like flies. The adult flies emerge over a period over a period of 10-14 days but each fly only lives about 24 hours. After mating each female inserts about 30 eggs in the surface of new boxwood leaves. The larvae hatch in about 3 weeks, and feed within the leaves from June through early fall. They spend the winter in the leaves, and pupate the following April. There is one generation each year.

What we can do: To control leaf miners, apply a soil drench of imidacloprid in May which will give season-long systemic control.  Alternatively, acephate can be applied in June to kill the larvae in the mines.

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