Boxwoods in the landscape not looking so good coming out of the winter? Are you seeing a lot of yellow leaves? Can you see any yellow-green-brown spots?
Carefully break open the leaf with your knife or finger nail, look for tiny orange pupae inside. These are boxwood leafminer pupae.
ADULTS ARE EMERGING and can be found on the newest leaves. The tiny orange midge adults resemble tiny mosquitoes and emerge out of last year’s leaves. Look closely to find empty pupal cases sticking out through tiny holes in the undersides of leaves. Adult midges lay their eggs into newly emerged leaves and those eggs will hatch into the next generation of leaf miners. Treating new foliage with insecticides (carbaryl, dimethoate, malathion) at the beginning (or just prior to) adult emergence can help reduce successful egg hatch and leafminer establishment in the nursery.
This pest is more common in the landscape than in nursery production. Insecticidal soap can be used to suppress adults in the landscape. Landscapers can also prune out new foliage in July/August. The clippings will desiccate, making it impossible for the freeloading leafminer larvae to complete their lifecycle.