You may think your tree somehow magically became decorated for Halloween a little earlier than expected, but in all actuality, you likely have tent caterpillars. There are two types of these that we typically see in Illinois and other parts of the Midwest, Eastern Tent Caterpillar and Fall Webworm. They show up in the Spring and Fall of each year, respectively.
Eastern Tent Caterpillar shows up in the April through June in a variety of trees. These caterpillars feed on the leaves and for the most part a cosmetic impact to your trees, but infestation on younger trees can impact health as the tree is trying to utilize it’s leaves to produce energy in the beginning part of the growing season. Tree health on younger trees can have more of an impact due to the reason that younger trees have fewer branches and significantly smaller leaf mass/area than mature trees. Physically removing the “tents” will suffice to control the infestation and this can be done by hand, tool or simply spraying them out with the garden hose. Some situations may call for insecticide applications, but an ISA Certified Arborist can help you best determine that.
Fall Webworm typically appears towards the end of the growing season in the autumn months. This one again is more of a cosmetic impact to your tree, especially because defoliation in the autumn is very minimal impact to tree health because it is preparing to drop it’s leaves anyways for the upcoming dormant/winter season. If control of infestation is desired, again simply physically removing the “tents” will suffice, insecticides are not typically recommended except for unique or extreme situations.
So, what to you do? Don’t leave the cobwebs in your trees for Halloween, simply get your garden hose and spray them out. If the tents are too high for your hose to reach, most likely it won’t be a problem because the tree is large enough to sustain the impact. When in doubt, you can always contact your friendly neighborhood certified arborist!