Bagworms
Bagworms are so named because of the “bag” they create around themselves to camouflage them from predators. This bag is created from silk they spin and small pieces of leaves they collect to protect themselves from predators. Young larva hatch typically in about mid-May and leave the bag they hatched from to find foliage to start eating. Larvae will usually feed on the plant they hatched on or one nearby but they can be carried to other plants via the wind and a long thread of silk. Bagworms will eat on just about any plant but prefer junipers or arborvitae. These insects usually will go unnoticed till their bags are 1-2” in size and hang from the plant like little Christmas ornaments.
The best control is achieved by starting control measures two weeks after the insects have started to hatch to ensure all the larvae are feeding which means we usually can start spraying around the end of May to the mid to latter half of June. There are several active ingredients that can be used to kill bagworms including Spinosad, permethrin, acephate, and cyfluthrin. Be sure to thoroughly cover all the foliage with the spray to kill the bagworms. There is unfortunately not a systemic insecticide on the market that is effective at controlling bagworms, the only control option currently available is spraying the foliage of the tree. If you don’t notice the bagworms till August when they are larger, it’s best to just pick as many bagworms off as possible and discard them since chemical applications at that point are usually unsuccessful.
