Bagworms are a common pest in North Texas, especially on evergreen species such as cedars, junipers, and cypresses trees. However, it is not uncommon to observe them infest broad-leaf trees like oaks, maples, and elms as well. While they are common, they may not always be noticeable, especially on evergreens, as they use material from the trees, they infest 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.
Bagworms, if left uncontrolled, can be quite devastating and defoliate major portions of an infested tree’s canopy quickly. We typically begin to see the impacts of these pests in mid-to-late summer with infestations peeking into fall.
TreeTech would like to offer some basic information to assist in the identification and control of these persistent pest.
What Are Bagworms And How Do They Behave?
- Bagworm is the common name for several different species of insect which are actually a type of moth (order Lepidoptera, family Psychidae).
- The bagworm caterpillars are very small (about 1/25 of an inch long), and spin silk thread which they use to attach themselves to plants and to weave into their bags.
Image of a typical casing of bagworms on a cypress.
- Unlike a typical cocoon, the bagworm’s casing functions as a moveable shelter, with the caterpillars exiting to find food and climb up the plant.
- Once the caterpillar has matured, it undergoes a metamorphosis period before emerging as an adult.
- Male bagworms resemble small moths while the females are flightless.
- Male bagworm moths seek out females during mating season, and the female uses her bag to lay eggs.
- The exact times of caterpillar and adult emergence varies from species to species and is dependent upon the weather.
Can You Treat For Bagworms?
While bagworms are not prevalent every year, once they have infested a tree, they will continue to live there unless controlled.
- The simplest control method is to manually remove the bags.
- They can be pulled off by hand or sprayed off with high-powered water.
- 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.
- Insecticide sprays can be used to control bagworms, but are most effective in early summer (June) when the caterpillars are small, and can be completely ineffective by late summer (August).
- Systemic insecticides applied as a soil drench may be used as a preventative measure to control infestations the following year. Consult a certified arborist to see if this may be a good option for you.
Image of the optimum time for spray control for and damage from bagworms. Credit: Kansas State
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