Bagworms – The Nightmare Before Christmas

October 9, 2019
Larry Hurley
Insects
0 Comments

Here’s something good you can do for your garden any time in the next six or seven months. Check your shrubs for bagworms and if you find them, remove them. They are easy to find, they are little brown sacks about two inches long, hanging from branches like ugly little Christmas tree ornaments from The Nightmare Before Christmas.

The adult bagworm is a moth. In June tiny caterpillars hatch from eggs laid the female moth (or the “moth-er”). As they feed, they make a silk sack around themselves to which they append little bits of sticks and leaves from the plants upon which they are feeding, usually needle evergreens. This serves to protect them from the elements, predators, and camouflages them from the eye of the casual gardener. You may not notice them until you see brown patches on your evergreen in mid-summer, with the bagworm hanging in the middle of the dead zone, pretending not to be there.

In late summer they stop feeding and go through metamorphosis from caterpillar to moth. The male leaves his bag and searches for a female. The female is a stay-at-home mom and never leaves her bag. The male visits, love ensues, and the female lays eggs in her bag, and then dies. The eggs overwinter in the bag, and the caterpillars hatch in spring and start the whole cycle again. If you catch them when they are recently hatched, they can be controlled with BT. This is an organic bacterial insecticide that only kills caterpillars. As such, you want to be able careful in application to avoid hitting non-target caterpillars.

Better still, if you can reach them, just pull off the bags now and put them in the trash. Half will be empty, having been the male bag, the other half will be full of eggs. Look especially on needle evergreens like dwarf Alberta spruce, junipers, and arbor vitae. That said, you may also find them on Japanese maples. A good gardener is vigilant, and looking for these pests is easy and saves a lot of grief come spring.

A good reference comes from the University of Maryland Extension Service Home and Garden Information Center (HGIC):

Larry Hurley, Retired Behnke’s Horticulturist

Larry Hurley

Larry Hurley worked at Behnke Nurseries from 1984 until the business was composted in 2019, primarily with the perennial department in growing, buying and sales.

Before landing at Behnke’s, he worked as a technician in a tissue culture lab, a houseplant “expert” at a florist shop, and inventory controller at a wholesale nursery in Dallas. With this and that, ten years passed.

When his wife Carolyn accepted a position at Georgetown University, Larry was hired at Behnke’s for the perennial growing department and garden center at Behnke’s Largo location.

In 2021, Larry and Carolyn moved back to Wisconsin to be closer to family and further from traffic. After 37 years in a shaded yard in Maryland, he is happy to have a sunny lot where he can grow all sorts of new perennials, if only he can keep the rabbits at bay. He also enjoys cooking, traveling, and the snowblower.