Bagworms on a Redbud Tree

Host Plants

• Bagworms are common pests of a wide variety of woody plants including deciduous and evergreen trees. More common hosts include hemlock, fir, arborvitae and juniper. Other deciduous hosts besides redbudd include sweetgum, sycamore and honeylocust. Bagworms are native to Pennsylvania.

Description

• The adult bagworms males are black moths with clear wings with a span about 1 inch. The females live throughout their life within the bags that they weave. Pest presence on tree is identified by the distinct, cone shaped bags that the larvae weave with their silk and pieces of plant material from host plant. The resulting bag is well-camouflaged and often hard to detect on tree. Young larvae are black with amber undersides and mature to a gray color with dark markings near the head.

Damage

• Younger larvae are not highly destructive and mostly feed on the upper layer or epidermis of foliage. As the pests grow larger, the feeding worsens. Foliage of broadleaf trees is all consumed, leaving only the veins while evergreen needles are eaten entirely. The bags continue to grow in size with the larvae. Serious feeding can defoliate trees. Cankers or swelling of tree tissue appear on twigs and stems where the bags were attached during the pupae stage.

Control

• Handpick and remove the bags from the trees between winter and late April prior to the hatching of eggs. Bags are often hidden very deep within tree foliage, and a single bag can lead to the emergence of a huge larvae population. Insecticides are most effective when applied early on new larvae before the pests have a chance to retreat into their bags. Recommended insecticides include products containing permethrin, spinosad, bifenthrin, carbaryl or Bacillus thuringiensis.