QUESTION:
What product do you recommend to combat bagworms /case moth?
ANSWER:
Just to make sure we are talking about the same thing, there are Bagworms that feed on outdoor plants and there are Casemaking clothes moths found indoors. Since you are in an eastern state I will assume it is the ornamental bagworms, which seem to be absent in the far western states. If it is the Casemaking indoor moths then control must begin with finding the source, which most often will be some animal fiber that the larvae are feeding on. This might be hair, feathers, or wool and other animal hair products. There are a couple of species of case making moths related to the Casemaking Clothes Moth that pop up now and then in southern states, and these are referred to as Household Casebearer or Plaster Bagworm, and they may be feeding on fungus that could grow on wet wood or on general materials such as spider webs and dead insects.
Bagworms outdoors are interesting critters, and heavy infestations, like any caterpillar infestation of a plant, can cause damage to the plants. These moths include about 2 dozen species in North America, and they have a weird life cycle. Females of some species never become adult-like and never leave the “bag” they constructed as a larva. The female deposits several hundred eggs within her case in the fall and then crawls out and dies, and these eggs hatch in the spring to become active larvae that leave their mother’s case. They immediately create their own silk case around themselves, often attaching bits of twigs to the silk, and drag this case everywhere as they feed. When the larva is mature it attaches its case firmly to a twig on the plant and pupates within.
Because the silk case is so strong and so firmly attached to twigs on the plant it will remain there into the next year, even though no live larva is inside. These can be physically removed and disposed of to eliminate the clutter and to point out which cases are new and active ones on the plant. Removing the cases in the fall also removes all of the eggs, so this will help to prevent new larvae from emerging on that plant. This could be time consuming on plants with a lot of cases, but if the homeowner is made aware of the benefit hopefully they will make the effort. On the other hand, if they want to pay you your hourly rate to do it for them, well, that’s pretty good money.
If spraying is needed many of the residual contact insecticides will be effective. An excellent active ingredient for many years for lepidoptera larvae has been carbaryl, as in Sevin SL. This can leave a few weeks of residual on the plant, depending on weather conditions. Pyrethroids like bifenthrin and cyfluthrin also are labeled well for ornamentals and do a good job. If the customer insists on something natural you also can consider the bacteria in Dipel or one of the plant-derived products such as an Essentria liquid concentrate.
View past Ask Mr. Pest Control questions.
Pest QuestionsMarch 22, 2012
