|
|
The larvae of lilac leafminers (Gracillaria syringella)burrow between the upper and lower sufaces of leaves, forming unsightly blotches in the leaves. Heavily infested shrubs look scorched. From 3 to 8 larvae inhabit one leaf. Once they are full grown, they emerge, spin webs around the leaves, and continue to feed until the leaves are skeletonized. Lilac leafminers make cocoons, which they cover with plant debris. They spend the winter in these cocoons on the ground under plants. Two or three generations occur a year, the last one in september. The adult moth of the lilac leafminer has brown forewings mottled with the silver, and two silvery bands across its middle. It spends winter in debris-covered cocoons under the plants. The moths usually emerge during May, and the larvae mature in July.
To control the leafminers, remove any rolled leaves and burn them. If the infestation is very heavy and much damage has been done, cut back branches to healthy growth. In July, before the insect grows out of the larval stage, spray the entire shrub with a strong insecticidal soap solution.
The boxwood leafminer (Monarthropalpus buxi) is the most serious insect enemy of boxwoods in the United States. This pest weakens shrubs by feeding on leaves. Foliage turns yellowish, new growth is stunted, and twigs may die. It's the larvae that are to feared. These 1/8-inch-long yellowish maggots feed on plant tissues. Oval, water-soaked swellings appear on the undersides of leaves.
Trim and destroy the infested leaves as soon as you discover them. Rake up and destroy any fallen leaves.
|