In the spring, it is common to see silk-like webs in the crotches of crabapple and cherry trees which are caused by the Eastern tent caterpillar.

In the autumn, a totally different creature called the Fall Webworm (Hyphantria cunea) makes its nest at the tips of branches on about 90 different species of trees.

This critter over winters as a pupae in the leaf litter or concealed in the cracks in the bark of trees. Adults emerge in mid-summer and lay their eggs on the surface of leaves. When they hatch, the caterpillars begin to feed and to form silken webs near the tips of the branches of the tree.

As the larvae (caterpillars) feed, they skeletonize the leaves and begin to build a protective tent around the feeding area. Fortunately, this is another of those situations which is primarily aesthetic in nature. In most cases, the infestations are not large and the tree loses only a small percentage of its leaves. In very rare cases, the infestation may be large enough to defoliate the tree. Even this is not considered serious since it happens in the fall when the job of the leaves is just about completed for the year anyway. Unless a tree is in a very weakened state for some other reason(s), it will easily survive a case of fall webworms.

Keep landscape trees as healthy as possible by proper watering, fertilizing, pruning, etc.

Since this problem is rarely considered serious, it generally does not require any treatment. However, here are some things to consider:

1. Hand Removal of Webs - If you have a few webs on a strategically located ornamental tree, you can simply remove the webs by hand. It is probably best to only snip off the tips of the branch if this will not leave a misshapen branch. Otherwise, just pull the tent apart and brush the caterpillars into a container of soapy water.

2. Use Bt - Since these are true caterpillars (not sawfly larvae), they can be killed by using the biological insecticide, Bacillus thuringiensis (Bt). This must be sprayed onto the leaves and eaten by the caterpillars. Therefore, on small trees, it may be necessary to use a stick to open up the tent to be sure that the spray penetrates to the leaves. Another option is to keep a close eye on trees that have been bothered by tent caterpillars before so that you see the first signs of feeding. This is before much of a nest has been begun.

3. Do Nothing - This will be the preferred option in most cases. Fall webworm tends to be a cyclical situation with some years experiencing a more severe infestation than others. This is due to the presence of natural predator insects which keep the fall webworm from becoming too prevalent.

4. Insecticides - There are pesticides labeled for use against fall webworm. The timing of the applications must generally be made before the webs become too extensive. Again, this is only warranted on select ornamental trees which, perhaps, are near the house or deck and the aesthetic damage is objectionable.

5. Do Not Burn the Tents Off the Tree!!!!! - All this will do is kill the stem involved. This causes more damage to the tree than doing nothing at all.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

Types of Insects

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