After being mostly absent for the past 3-4 years, the Fall webworm is back in town and much more noticeable this year. They never really left completely, but the population has developed enough this year to be noticed. The Fall webworm is a moth that infests Pecans and other hardwood trees and creates unsightly webbing tents on the ends of limbs in the late summer. What you see is the caterpillar life stage of the moth. The caterpillars leave the webbing when mature and drop to the ground to pupate and overwinter.
We may not like how the tree looks when infested, but the harm to the tree is minimal and Tree Shepherds does not recommend control measures except in these cases:
1) The infested tree is over a patio, or sitting area, and the insect droppings are a mess on furniture, decking, etc.
2) The infestation level is high enough to cause harm to the tree (rare)
The Fall webworm actually has two generations per year in North Texas. The first generation occurs in May-June and the second generation about 60 days later in late August-September. This is the generation that we notice.
If the caterpillars are actively feeding, then control can be accomplished by:
1) Pruning off the web covered part of the infested limb
2) Breaking the webbing apart to allow birds and predatory insects access to the caterpillars
3) Breaking the webbing apart with a strong stream of water from a hose-end sprayer with a cap full of Dawn dishwasher liquid in the hose-end sprayer bottle.
4) Spraying with Bacillus thurengensis (BT) insecticide. The webbing must be broken apart and penetrated with the spray stream for the insecticide to be effective. This is a biological insecticide that is deadly on caterpillars but won’t affect other insects or animals. It will kill actively feeding butterfly larvae, so be careful if there are butterfly attracting plants in the vicinty.
Please don’t spray any other type of insecticides. Even if it is labeled for Fall webworm, these insecticides will kill most insects, including the beneficial insects that work to keep the Fall webworm populations down.
The best approach is to let nature take its course, but if there is a need to control, Tree Shepherds can work with you to manage this pest in a responsible manner that protects the beneficial insects and the other forms of life in your garden.