2 Sure Cures for the Bagworm Blues

If you live in the eastern U.S., you've probably seen your share of bagworms (Thyridopteryx ephemeraeformis) . It's not uncommon for large infestations to plague forestland along neglected roadways or, if you're unlucky, within your own landscape.

Bagworms spin cobweb-like "bags" in trees and shrubs. They particularly like to infest conifers such as pine, cedar, arborvitae, Leyland cypress and juniper. Sometimes, they're so prolific that they kill their host tree. Because the bags are shaped like pine cones, they often pass unnoticed in conifers--until it's too late.

Bagworms may also spin cocoon-like nests in deciduous trees, such as locust, maple, linden, sycamore and boxelder. Although these trees may suffer damage, unlike conifers they're rarely killed by bagworms. Nevertheless, few homeowners want even one bagworm nest in their yard.

Bagworms are actually moths in their larval (caterpillar) stage of development. After hatching, moth caterpillars spin cocoon-like bags. These bags have pieces of leaves from the plants they're feeding upon attached to them.

At first, the bags are very small--only about 1/8 inch long. The young bagworms move about freely as they feed, carrying their bags with them, enlarging it as they themselves grow bigger.

It's at this point--when moth caterpillars are young--that they're easiest to destroy through the application of a bacteria commonly called BT.

Bagworm-killing bacteria

Bacillus thuringiensis (BT) is a bacteria that kills certain insects, including bagworms, but it doesn't adversely affect humans or other animals.

BT works extremely well against young moth caterpillars, so if you're going to use BT, be sure to apply it early.

Common brand names of products that contain BT include Dipel, Caterpillar Killer and Thuricide.

Pesticides

These insecticides are also labelled for bagworm management: Bifenthrin Pro Multi-Insecticide, Onyx Insecticide, Talstar F, Talstar Lawn & Tree Flowable, Talstar GC Flowable, TalstarOne Multi-Insecticide and Dursban 50W.

Like BT, they should be applied shortly after the moth eggs hatch.

Handpicking

Removing bagworm bags from trees by hand isn't as gross as it sounds. Remove the bags in winter or early spring (before the moth eggs hatch) and destroy them.

You may have heard of gardeners pouring gasoline on bagworm bags and then setting them on fire. It's a dangerous practice that could cause serious damage to you, your tree and/or your property. Don't try it! Stick with handpicking the bags when the eggs are dormant. Or, if your infestation is severe, opt for BT or some other non-petroleum chemical solution. Those are the best ways to beat the bagworm blues.