Bagworms are a common pest in North Texas; While bagworms are not prevalent every year, it is important to know how to spot and handle them to keep your trees healthy. Once they have infested a tree, they will continue to live there unless controlled.
Bagworms are especially common on cedars, junipers, cypresses, and other evergreens, although they can attack broad-leaf trees (like oaks, maples, and elms) as well. While they are common, they may not always be noticeable, especially on evergreens where they use material from the trees to camouflage their casings. Like other insects, bagworms have a year-long life cycle, and control measures depend on the growth stage of the pest.
WHAT DO BAGWORMS LOOK LIKE?
You probably won’t see the bagworms themselves, but instead, the 2” homes bagworms make in your trees. In the fall, the insects use their silk and pieces of the tree to create a camouflaged, cocoon-looking bag, which they fill with up to 1,000 eggs!
The eggs hatch in late spring or early summer when super tiny, black larvae emerge. At 2mm, they’re barely larger than a pinhead, which makes them light as a feather. The caterpillars use their silk thread as a parachute to travel to nearby trees and begin building a new home (or bag) there. The pests hang out in their bags until late summer or early August when the adult males emerge to mate. Male bagworms are ashy-black moths with transparent wings and are about the size of a quarter.
WHAT DAMAGE DO BAGWORMS DO?
On evergreens, they’ll eat lots of the buds and foliage, causing branch tips to turn brown and then die. But if they eat more than 80 percent of the tree, the entire evergreen may die. On deciduous trees (those that lose their leaves in winter), bagworms chew small holes in the leaves and can cause defoliation. Generally, these trees will bounce back if you get rid of the bagworms.
HOW CAN I GET RID OF BAGWORMS ON EVERGREENS AND OTHER TREES?
You aren’t going to like this, but the easiest and most simple way to remove bagworms is to cut off the bags by hand and destroy them. Be sure to cut off all their silk, too, because that could strangle (and kill) twigs later. It is important to dispose of the bags or destroy them, and not just leave them lying on the ground, as the eggs they contain can hatch and re-infest the tree. Fannin suggests that you put them into a plastic trash bag and send them off with the garbage.
If that’s too gross or there are too many bagworms for you to remove, we can help! Insecticide sprays can be used to control bagworms, but are most effective when the caterpillars are small and can be completely ineffective if the bagworms close their bags which occurs if they molt or during the winter. Systemic insecticides may be used in some cases as a preventative measure.