Bagworms and Control Tips
bagworms and give background on this interesting insect plus control options. I will be sharing information from two researched based sources. One is a UGA publication revised by Tim Daly, UGA ANR agent in Gwinnett County and another by M.F. Potter and L. H. Townsend from the University of Kentucky.
Bagworms can be a damaging caterpillar, but it can also be interesting to follow their life cycle. Most folks will know bagworms by the unique spindle shaped bags they will form. They not only will construct, but will live inside these 1- 2 inch bags. Bags have a silk like casing to the inside, but the outside is covered with layers of leaf, twig and bark pieces. The bag is tear shaped with an opening at the large end that will allow for the caterpillar to make repairs to the bag, plus allow them to eat. Bagworms will feed on a variety of evergreen and deciduous trees and shrubs, but can cause more feeding damage to juniper, arborvitae, spruce, pine and cedar.
If the bagworm population is high, they can actually strip items of their foliage which can lead to death of that ornamental. The damage can go unnoticed for a while because people will see the bags and mistake them for cones that are normal for that ornamental. Obviously I don’t like damage to my ornamental plants or trees like the next person, but if you ever stop and research the life cycle of insects, it can be very interesting. I will share some information on the life cycle that will hopefully explain where we should be right now in bagworm development.
Bagworms that can cause feeding damage on plant foliage this year normally will hatch in middle to late May from the protective bag. When they hatch from the bag, they will start looking for food. The caterpillars will be pretty small in size at this point. The bagworm will make a small bag out of silk and plant material. The bag can look almost like an upright ice cream cone with the bag constructed around the hind part of the bagworm.
As the bagworms continues to feed on shrub or tree material, they will grow and will keep making their protective bag larger so they can go up into the bag when they are threatened. I normally will start getting calls in late July or August about the damage that a client will start realizing they have on certain trees or shrubs. By early fall, the bagworm will permanently hang or suspend their bags on the tree or shrub so they can go through a pupation stage to turn into adults. The bag at this point is 1.5- 2 inches in size.
The male bagworm will develop into a moth that can fly. The male adult bagworm will be black in appearance and furry with clear wings. The adult female is more grub appearing and cannot fly. She will be more creamy white with no wings or legs. She will produce a pheromone that will attract the flying male moth. After mating, the female can lay hundreds of eggs in attached bag. The adult female will die after laying the eggs. The eggs will stay in the bag until hatching the next May. The young hatched larvae can be carried by wind on silk strand while larger larvae move by crawling.
If you need to control bagworms, hand removal of the permanently attached bags in the fall, winter or early spring months may be a good option if you see the bags on only a few ornamentals. Weather will not be hot and you are getting them before the May hatch of the new generation of bagworms. I would not suggest hand removal on tall ornamentals that could be unsafe for the person. No reason to remove high on an ornamental and risk injury from a fall. Spraying insecticides for control is best when the larvae are less than .50 inch in size. This would be normally June, so this could be a good time to investigate ornamentals that bagworms prefer. My handbook mentioned some of the Bacillus thuringiensis products such as Biotrol WP, Thuricide or SokBt. It also mentions Malathion 57 EC and states various pyrethroids as there are a variety of home formulation for broad spectrum contact insecticides. I will remind clients to read the label of any product used for safety and warnings plus any application procedures. You can also read the label to make sure it states it can control bagworms. It could be unfeasible to spray anything up in and ornamental due to drift of the insecticide back on the person.
For more information, contact UGA Extension- Gordon County at 706- 629- 8685 or email gbowman@ uga. edu.