Q How can I control leaf miners in columbine and lilacs? In the spring, almost every columbine leaf is full of tunnels. Not only are they unsightly, but they weaken the plants. J. S. Logansport, Ind. The adult of lilac leaf-miner is a small brownish moth with six yellow stripes on its forewings. It lays eggs in May and July and tiny larvae enter leaves in June and August.
Products with Bacillus thuringiensis (effective against larvae of moths and butterflies) can be sprayed on plants about the time iris bloom in June and again about mid-August. Be sure to cover undersides and upper parts of leaves.
Columbine leaf-miner adults are brownish flies, so larvae are not susceptible to BT. Malathion is effective if sprayed as larvae emerge from eggs under leaves.
Some of our readers tell us hot pepper-garlic spray is effective against leaf miners. Pressing the tunnels firmly with thumb and forefinger, although tedious, can eliminate considerable numbers of larvae.
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