Bagworms
Caterpillars that live inside spindle-shaped silk bags covered with bits of leaf and strip evergreens and other shrubs of their foliage.
Also known as: Bagworm moth
Symptoms and identification
Small, brown, cone-shaped bags, 2 to 6 cm long, hang from branches and look like dead fruit or cones. Foliage is eaten in patches, and heavy infestations strip conifers bare, which may kill them because evergreens do not regrow quickly.
Causes
Eggs overwinter inside the female bag and hatch in late spring. The young caterpillars spread on silk threads on the wind, build their own bags and feed through the summer.
Organic treatment
Hand-pick bags and drop them into soapy water, doing it before eggs hatch in late spring. Spray Bacillus thuringiensis (Bt) on young caterpillars in early summer, since large ones are hard to kill.
Prevention
Look over trees and hedges in winter and early spring and remove bags. Check evergreens regularly from late spring.
Chemical treatment (use with care)
Use an insecticide labelled for bagworms on that plant, applied while the caterpillars are small, following the label.