Bagworm

My colleague Newton Hogg used to say “When I can see their damage at 50 miles per hour, I KNOW someone has a serious problem with bagworms.”

I was driving down Roosevelt Highway in south Fulton county when I saw a juniper infested with bagworms. I hopped out to take a picture for you!

Juniper, Leyland cypress, arborvitae and cedar trees can be skeletonized in late summer by bagworms. Examination of a rapidly disappearing shrub reveals dozens of brown "bags" hanging from the limbs. The bags are made from the plant's needles and they contain an adult moth larva, who feasts on the plant's greenery.

Once a larva has eaten enough to satisfy it, it attaches itself to a branch or nearby surface to pupate into the adult moth. Males emerge from their bags, females do not. Males mate will females, who lay their eggs in the bag, protected from winter and pesticides.

By understanding the bagworm life cycle, a control strategy can be designed.

Young bagworms who are actively feeding can be controlled with one of the organic caterpillar killer products that contain Bacillus thuringiensis (B.t.). Garden insecticides that contain acephate, bifenthrin, esfenvalerate or permethrin are also very effective.

Feeding begins in June and lasts until late July, depending on the weather. Examine the bags and the shrub to be sure the larvae are actively feeding before depending on chemical control to do the job.

After mid-August, when the insects are inside their bags, it is too late to control the pest with insecticides. The bag protects its inhabitant securely. At this point there is no solution except hand removal. Wear a long sleeved shirt to avoid being scratched by the needles and scales of the host plant. Make a note to spray insecticide next June, when the moths have not yet formed their protective bags.


bagworm after pupation begins


Bagworm larva feeding on juniper