bagwormIt’s no secret that there are many varieties of insects that can damage your trees and shrubs, but it’s amazing how many people have plants destroyed by bagworms in their landscaping without even noticing until it’s too late. Often we are called onto the scene in mid-late summer to diagnose a browning tree or shrub in a landscape that “seemed to change overnight”. However, if it’s bagworms you’re seeing, it could have been happening for 4-6 weeks without you noticing.

Bagworms (Thyridopteryx ephemeraeformis) are a common pest in our area. This  larval stage of a moth has been documented feeding on over 100 different plants. When bagworms feed on deciduous plants, those species have a chance of regaining leaves in the next season. However, when bagworms attack an evergreen plant, it isn’t so fortunate. These plants are often destroyed within a short period of 1-2 months.

Know Your Plants: If you can’t identify the variety of plants in your landscape, find a reputable and knowledgeable tree care company that can assist you with this task. Since bagworms only attack specific plants, identifying potential damage candidates in your landscape will allow you to focus your attention. Bagworms will most commonly be seen feeding on Arborvitae, Fir, Hemlock, Juniper, Pine, Cypress, and Spruce.

Young bagworm Larva

Photo courtesy of Sandy Feather – Penn State Cooperative Extension –

Know the Bagworm: These worms will form cone-shaped bags, which are constructed with a silk they produce and interwoven needles and leaf tissue from the plant they are feeding on. This camouflaged casing allows the bagworms to feed with part of their body out as they hide from predators. Egg hatch typically occurs in late May – early June in our area with the new larvae measuring less than a half of an inch. They are very difficult to spot when young because of this small size. As they feed, they quickly grow to 1″-1.25″ long, as well as their protective bag gets materials added to it to increase in size as well. Bagworms feed through late August until they pupate and turn into the adult moth. At this time, breeding begins and female bagworms will lay 500-1000 eggs in each bag! That can mean a lot of bagworms the next season!

spraying for bagwormsKnow How to Control Them: The sooner in their life cycle you treat, the easier they are to control. This means the best strategy is to spray sometime in June through early-mid July. At this time, the bagworms are smaller and their bag, in turn has less leaf tissue constructed around them. This makes it easier to deliver an appropriate insecticide to them for control. The later in the season you wait, the more difficult it is to control them, and the greater the need for stronger insecticides. Bagworms can also be hand-picked off of smaller plants, but spraying is preferred because often some pests are missed. Homeowners are able to purchase labeled insecticides at home & garden centers. However, sometimes trees are so large, or shrubs so dense, that commercial applicators are more effective in treating this pest.

Like most tree insect control and management, the best approach is a proactive one. Scheduling a spray for bagworms by a tree service in early summer each year can prevent a problem from getting bad enough that significant damage occurs.

If you follow these tips, control of this pest is “in the bag”!

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