I have Tent Caterpillars my Royal Raindrop Crabapple trees. I have been told that I have to burn them out or cut out the branches to get rid of them. This would leave a large hole in my tree. Do you have another option? Also should I get rid of them do you have an idea for a preventative maintenance? Thank you Marie Guyer
Deschutes County Oregon
Hello Marie, normally the recommendation is to prune out the webbing and burn the pruning material. You wouldn't want to burn the branches in the tree. I like to suggest that you put the prunings in a black trash bag, tie it up tight and set it out in the sun for a couple of days, then get rid of it in the trash. Other options for control once the webbing is created is to use a strong stream of water to break open and destroy the nest. This exposes the caterpillars to predators and knocks some of them out of the tree. The nest will likely be rebuilt so it will have to be done more than once. A technique I like to use on shorter plants is to sweep the nests out with an old broom then stomp on the caterpillars caught up in the broom.
Early on when the nests are still very small you can spray Bt variety kurstarki on the tree leaves near the nest. As the caterpillars feed on these leaves they will ingest the bacteria and it will kill them. This works best on young caterpillars.
Marie, sorry, i forgot to mention that if this is happening in the fall the caterpillars are called fall webworms as they are the larvae of the fall webworm moth. They create a similar webbing nest as the tent caterpillar we see in the spring.