Ask The Arborist: Bagworms
What are these mobile bags of destruction on my most prized plants?
Those contain bagworms. In your trees and plants, they do anything from eat and nest to reproduce by the hundreds. One season you will see only a few and the next there will be many more than you anticipated (about 500-1000 eggs per bag). All the more reason to act fast when they are first spotted.
Identification is the number one thing to consider when you are planning to control a pest. Bagworms are easy to spot by their dangling bags on plant material. They are anywhere from one to two inches long and are usually brown in color. Inside are little pupae. At this point in the season they are young male and females which do not start mating until September. In the beginning of summer, they poke their little heads out and move along branches and stems eating or collecting needles or leaves to add onto their bag. This can result in a devastating amount of defoliation if left untreated for too long. The most common host plants are a selective group of deciduous trees and shrubs as well as a wide range of evergreens. Sometimes a pine cone can be mistaken for a bagworm, so take care to be very observant.
Controlling bagworms can be very simple and there is plenty of ways to do so. If you just have a few of the little buggers hanging out you can just pluck them off and discard them. We suggest burning or drowning them in soapy water because they have a sneaky way of moving around and finding their way back to your beautiful tree or shrub. If you have a lot of wildlife living in your backyard, bagworms become a great meal for the birds during the fall and winter seasons. Late June to early July is the suggested time for spraying the pupae. There are pesticides available from your local nursery, but follow the label to get the most effective results. Preventive injections can also be done on an annual basis. CM’s tree care program offers prevention and treatment of these harmful insects.