I understand that picking the bags in fall and applying Bt (kurstaki strain) in spring is the prescribed method of control. My daughter has four tall trees (arborvitae Thuja) that can't be reached by hose sprayer--need to spray 40 ft high. I don't want to pay thousands of dollars for a commercial sprayer. Is there an alternative systemic soil drench that work--I hate killing beneficial predators but... My daughter lives in Virginia and I live in Howard County. Thanks
A soil drench would not be effective for controlling bagworms. The trees do have to be sprayed. The bags can be removed any time of the year. Put the bags in soapy water do not simply throw them under the tree. Bt sprays are made as soon as the bagworms hatch. In general, that happens around Memorial Day in MD but is probably earlier in VA.
So a systemic soil drench of an insecticide wouldn't get into the needles ? I assumed the worms eat from the tree.
Do you know of a sprayer that would spray a 30 ft tree and be affordable?
A systemic treatment would not be effective at this time of year because translocation (movement of materials) in plants is in a downward direction now. Systemic treatments are best applied in the spring when translocation is upward toward the leaves/needles to support new growth. There is a type of sprayer you can buy called a "tree sprayer." In order to reach a 30 ft heigh effectively, you will need to have good water pressure.