Bagworms

The Bagworm, Thyridopteryx ephemeraeformis, often gets mixed up with the fall webworm. Their life cycles cross paths during the summer months. They not only differ in their appearance, but they differ in the type of silken structure that they produce. The bagworm caterpillar is dark brown and forms a cocoon-like bag that hangs from the host plant, while the fall webworm is yellowish or lighter brown covered with long silky gray hairs that builds a larger silken tent over the branches of the plant where they feed.

The eggs usually hatch in June and come from last year’s old bags. The new born caterpillars will start to form small bags on the outer foliage on plants in full sun. The new bags are covered with plant parts from the host plant that they are feeding on throughout their life. One generation occurs each year.

The bagworm moth can cause serious damage to many types of plants. It feeds on cedars, arborvitaes, junipers, Leyland Cypress, white pines and other conifers. They have been known to feed on many broadleaf trees and shrubs including sycamores, rose, elm, locusts, willows, oaks, maples, and many more.

The damage is most serious and obvious on foundation conifers, such as arborvitaes and junipers. They may defoliate branches or even entire plants. On very large deciduous trees and shrubs, defoliation is usually less evident.

How can Virginia Green help?

In light infestations, they can be handpicked and destroyed. With heavy infestations you normally see around this time of year,  Virginia Green can treat with an insecticide. Treating infestations in the early summer when they are first noticed is important. Once treated the bags may remain on the plant and take years to disappear, but the caterpillar is dead.

How do I know if the old bag on my plants have eggs in them or not? Old bags usually look grayish or brown. Active bagworm bags have green plant material attach as camouflage on the outside. The larger bags are usually one to two inches are the ones that might have eggs in them. These bags tend to be higher up on the host plants. When they hatch out in late spring and you see little bags hanging on the outside branches of the host plants, then you know you have active bagworms. We at Virginia Green can be out to treat these pests in our from Round 4 – 7 Tree and Shrub applications. Call or contact us for a free landscape inspection of this camouflaged pest.