Bagworms-June Is the Time to Treat

What is a bagworm?

June is bagworm season.  Many people don’t realize they have bagworms because they camouflage themselves.  They form a 1 ½ – 2-inch bag that hangs downward from the branches and is gray or brown colored.  Many people mistake them for small pine cones.  But inside that bag is the female bagworm and, depending on the time of year, all of the eggs she has laid.


The bagworms attack both deciduous trees and evergreens, but their favorite plants are juniper, arborvitae, spruce, pine and cedar.  Bagworms wrap a strong piece of silk around the branch or twig to attach themselves.  This can girdle the branch and cause it to die.  Sometimes this damage doesn’t show up until the next season when the branch grows bigger and is strangled.  Bagworms also strip the plant of foliage as they eat.  To move from plant to plant, bagworms can either suspend themselves on silk and let the wind carry them or larger larvae can crawl short distances.

Life Cycle: 

By early fall, the larvae permanently suspend their bags.  Males emerge as furry black moths with clear wings about an inch wide.  The females don’t develop into moths, but remain worms and wait inside their bags.  They emit a strong scent to attract the males who mate through a hole in the bottom of the bag.  After she has laid several hundred eggs inside her bag, she dies.  The eggs will hatch the following May and crawl out of the end of the bag in search of food.  They use silk that they produce along with plant materials to make a small bag around their hind end.  This gives them the appearance of tiny ice cream cones.  As they feed and grow, they enlarge the bag and hide inside if disturbed. In fall, they form their bags and the cycle starts over.

How to treat them:

  Adult bagworms can be cut off with a knife or garden shears, but you must be sure to cut the silk band that holds them to the branch so it doesn’t remain and girdle the branch.  This works well with small infestations on smaller trees.  But many times, infestations can be widespread or occur on taller trees that make physical removal difficult.  Then, insecticides are your best choice.  The best time to use insecticides is June because the small larvae are more vulnerable to insecticides.  Call Heritage if you need help getting rid of bagworms or any insects on your trees, shrubs or lawn.  We can take care of it for you.