What is my shrub dying and what are those “pinecone” things hanging from the branches? We hear that a lot in this area, especially in this extreme heat when your trees are already in a stressed state.

If you do see bags made out of needles or leaves on a woody plant that is defoliated the chances are you have bagworms. Bagworm caterpillars make distinctive 1.5 to 2 inch long spindle-shaped bags that can be seen hanging from twigs of a variety of trees and shrubs.

Bagworms prefer juniper, arborvitae, spruce, pine, and cedar but also attack deciduous trees. Female moths cannot fly but the larvae can disperse. Very small caterpillars can spin strands of silk and be carried by wind, an activity called “ballooning”. Larger larvae may crawl to adjacent plants.

Bagworms pass the winter as eggs (300 or more) inside bags that served as cocoons for last year’s females. The eggs hatch and the tiny larvae crawl out to feed. Each uses silk and bits of plant material to make a small bag that protects and camouflages it as during feeding and growth.

Bagworm caterpillars feed for about six weeks, enlarging the bag as they grow and withdrawing into it when disturbed. Older larvae strip evergreens of their needles and devour whole leaves of susceptible deciduous species leaving only the larger veins. When abundant, the caterpillars can defoliate plants.

Heavy infestations over several consecutive years, especially when coupled with other stresses, can lead to plant death.

Should you see these telltale bags hanging on your trees or shrubs, please call Wood Acres Tree Specialists to assess and treat the damage before the stressed plant can’t recover  -or its natural form and beauty is ruined for years.