Dear Rodney,
Last year I had problems with bag worms. Is there anything that I can do now to head them off?
Thank you, Debbie
Dear Debbie, You were not the only person to have bagworm issues last year. Many homeowners felt overwhelmed and called the local pest control to hit their yard with a general pesticide that is non-specific and kills everything, good as well as bad insects. There is a better way that is more environmentally friendly that targets only the bagworms and now is a good time to start preparing to determine when the worms are most vulnerable.
Bagworms feed on foliage of evergreens, roses, and often other trees and bushes. They protect themselves by building a “bag” of web and plant material, usually evergreen needles that they add to during the summer months as they grow. Once in their bag, they are very hard to treat with a spray that will not penetrate their bags and your recourse is to hand pick them when you see them.
Worms can be treated easily if you catch them in the right life stage. Worms hatch out in the early spring and begin feeding shortly thereafter. As they feed, they begin gathering materials to build their protective bag. Male and female worms grow in their bags until fall when the males morph into moths and find female worms to reproduce. Females never leave their bag and in time the female lays eggs in her bag, dies, and the eggs over winter, protected by the bag. When the weather becomes favorable in spring the eggs hatch and begin the next cycle.
Look around your yard now and pick about 15 bags off your trees and shrubs and put them in a sealed plastic bag or jar. The bags that you will find are either abandoned male bags or female bags that contain eggs. Place the bags where they are exposed to outside temperature, out of the light, and watch the bag. When you start seeing tiny worms moving about in the bag, it is time to treat for them. It is important to treat while the worms are tiny and actively feeding before they can build their bags.
I recommend using a spray of Bacillus thuringiensis or BT. This is a naturally occurring bacteria that makes toxins that affect immature insects (larva/caterpillars) when they eat it. The bagless larva will eat foliage that has been sprayed with the BT solution and get very ill. BT does not affect a wide range of insects like most chemical pesticides and the bacteria are only active for a few days after they are sprayed on your trees and shrubs. The bagworms have only one cycle a year, so at worst case you will have a lot fewer worms this summer.
Last year BT sold out quickly during the army worm problem and currently stores have it on their shelves. You might want to purchase a couple of bottles while there is plenty available.
Resources
https://agrilifeextension.tamu.edu/library/gardening/bagworms/
If you would like to ask Rodney a gardening question his email address is [email protected].