Are Those Nature’s Christmas Tree Ornaments?
The small collection of twigs and dead leaf parts hanging from your evergreen and/or broad-leaved shrubs and trees might be Bagworms (Thyridopteryx ephemeraeformis; bags often containing eggs), not natural Christmas ornaments. Although bagworms are not observed “en-masse” every year, once a plant is infested this insect becomes a tenacious problem unless kept in check. One year I thought I had just a couple on my arborvitae and removed them (they were very well attached) until I viewed the tree from the bottom, looking up into the middle. Not a happy surprise to see all the hideaways that still needed removing before they had a chance to emerge and reproduce.
Bagworms’ most recognizable characteristic is the tough, portable, cone-shaped case they build to live in. The silken texture of the bag is hidden and reinforced by layers of leaves, twigs, and bark fragments arranged in a crosswise or shingle fashion. Different species use different plant materials to make their bags. Female bagworms lay 500 to 1,000 eggs in their bag before they die in the fall. The eggs overwinter and hatch out in May and June.
As the larvae hatch, they spin single threads of silk and attach to adjacent limbs or plants, where they begin building their own silk bags. Young larvae begin drifting or “ballooning” on the silk thread, reminiscent of James and the Giant Peach by Roald Dahl. These new bagworms may lay claim to new territory, spreading the infestation to new host plants.
New bagworm infiltrations are not easily spotted until they grow big enough to consume a lot of plant material off the branches, usually by late in the summer. These bags will likely contain eggs that will hatch out bagworm larvae the following spring. Proactively scouting for bags in winter will save time, money, effort and damage later in the plant’s lifetime. The same trees and shrubs will be damaged year after year as populations build. Remember each bag could contain 1,000 eggs so picking them off in fall and winter could make a big difference in spring.
To read more about this insect for intervention and recommendations on control go to the Bagworms in Ornamental Landscapes publication or contact your local N.C. Cooperative Extension office.
Minda Daughtry is the Horticulture Agent for North Carolina Cooperative Extension in Lee County.