Bagworms

This is the time to inspect your evergreens and other trees for bagworms. Bagworms damage plants by defoliating them. Heavy populations kill many ornamental arborvitae and junipers.

The bagworm gets its name from the spindle-shaped silk bag that the caterpillar carries around as it feeds. Because the bag is covered with pieces of leaves and twigs from the host plant, the bag of a worm feeding on juniper will not look the same as the bag of one feeding on roses.

To rest, a larva attaches its bag to a twig with silk. The insect pupates in late summer, emerging in about week as an adult. Males fly and search out bags containing females. After mating, a female lays up to 1,000 eggs in her bag and dies.

If you can reach them, pick the bags off the host plant and destroy them. Mark also recommends the insecticide Cygon. Take action when you first notice the bagworms, since small larvae are easier to kill.