This is the time of year for many of our fall pests to begin rearing their ugly heads. One caterpillar that I have noticed showing up in Miami Valley landscapes in good numbers is the fall webworm.
Don’t get this confused with the Eastern tent caterpillar (ETC) or bagworms as many do. They are all caterpillars but they all have different habits.
Let’s start with the early season ETC. This caterpillar typically hatches in central Ohio in the spring, around the time that the star magnolia begins to flower.
The fall webworm doesn’t actually hatch in the fall but rather has a first generation that hatches around the time that the oakleaf hydrangea starts to bloom. The second generation of fall webworm hatches in the summer.
The name fall webworm is due to the fact that the second generation reaches their maximum size in the fall.
Both of these caterpillars build nests (many call them “tents”) in a variety of deciduous trees. ETC prefers those trees in the Prunus or cherry family but they can also be found on apple, crabapple, hawthorn and maple as well. Fall webworm has a wide variety of deciduous trees that it will live on.
An easy way to identify the two caterpillars is to look at their nest or tent. ETC builds their nests in the crotches of the trees. At night, the caterpillars venture out to the leaves to feed and return to the tent. There is only one generation per year.
The fall webworm builds their tents towards the ends of the branches and the tents envelopes the leaves inside of the tent. They stay home and feed on the leaves.
Since there are two generations per year, the first generation adult moth lays her eggs on or near the already-created tent. This second generation then really expands the tent and really makes it so much more noticeable. In fact, I just noticed last week that I had some in my pagoda dogwood.
Now bagworms are totally different from the above two caterpillars in their habits. They make their own house and carry it around on their back. The other two caterpillars are social and hang out together whereas bagworms tend to go it solo (though you will find more than one on a plant).
Bagworms primarily feed on evergreens but also feed on some deciduous plants. They take needles and leaves and make their own nest, securing themselves inside. They can strip evergreens and can be a real problem.
The ETC and fall webworm are major problems and can be managed by destroying their nests or tents and smashing the caterpillars. Since fall webworms are found near the ends of the branches, you can prune them off and destroy.
Pesticides are not effective once all of these create the nest and protect themselves. You can control them early with Bt or bacillus thuringiensis but you have to get them when they are first hatching and tiny.
Now that you know how to identify them, you can look for control options at your local garden store or on the Internet.