Phenology & Eastern Tent Caterpillar

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Tent CaterpillarHave you ever heard of the term “phenology”? The Merriam-Webster dictionary defines phenology as a branch of science dealing with the relations between climate and periodic biological phenomena such as bird migration or plant flowering. So, what this means is that we can use the development of plants during the growing season as an indicator of when certain insects may appear in the landscape.

A great example of using phenology this time of year is the Eastern Tent Caterpillar. You can correlate the hatching of the Eastern Tent Caterpillar eggs to when our native tree the Eastern Redbud begins to bloom which is also about the same time that wild cherry leaves begin to emerge. You will notice the webs or “bags” of the newly hatched caterpillars as they are built in the crotches of trees. This caterpillar’s favorite host plants are wild cherry, apple and crabapple. It can also be found on other fruit trees and native trees such as Eastern redbud, ash, birch, maple, oak and others.

The bags protect the caterpillars from predators. They return to the bag in the evening and will remain in it during inclement weather. Eastern tent caterpillar can easily be controlled when the bags are small by simply tearing them open to expose the small caterpillars to bird predators or you can remove the entire web and dispose of it. Damage done to trees from feeding does not harm the trees as they have evolved for many years with this insect. The damage of lost leaves occurs early in the season and new leaves will be produced to replace those lost to feeding.

Once mature, the caterpillars leave the tree to look for a place to pupate. They will build a white cocoon to pupate in which they will attach to tree trunks, fences, brick mortar, patio furniture, container pots, and many other things. The adult moths emerge in late June or early July to mate and begin the cycle over again. Females lay their eggs on stems about the size of your little finger and the egg mass looks like a brownish-black bump on the stem that has been varnished. You can monitor your trees in the fall and winter for the egg masses and hand rub them off or prune them out to reduce the number that will appear next spring.

Did you know that it takes thousands of caterpillars to feed one clutch of baby birds? If you like seeing birds in your garden, don’t destroy or spray these caterpillars, just open up the webs so the birds can use them to feed their babies.