Caterpillar Infestation of Oak Trees

A reader from Tennessee recently wrote to us about an oak-tree infestation involving caterpillars or worms. The worms (or caterpillars) have been eating the leaves of the oak tree, and there are evidently so many that the reader claims to hear the creatures eating the tree. Moreover, many of the caterpillars or worms fall from the oak tree during the night, leaving a driveway covered with cylindrically-shaped, dead bodies in the morning for our poor reader to confront. There can be no question that our reader is dealing with a relatively serious worm or caterpillar infestation that is compromising the vitality of an oak tree.

The creature in question is primarily brown, although its underside is often a light color. What are these things – worms, caterpillars, or something else – and how do you get rid of them?

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Let’s begin with the first question. The reader is probably dealing with one of two pests, both of which are caterpillars: the tent caterpillar (sometimes called “tent worms”) or the gypsy moth caterpillar. There are actually two types of tent caterpillars – the eastern tent caterpillar and the forest tent caterpillar – but the reader’s infestation sounds more like the latter, so that is what we’ll focus on. Forest tent caterpillars prefer hardwoods, like oak trees, and they have a brownish body and blues lines on their sides. Mature caterpillars can grow to be two inches long, and some of these older caterpillars have white strips on them. Although forest tent caterpillars (and eastern tent caterpillars, for that matter) are unsightly and a pain to deal with, the defoliation they cause rarely kills a healthy tree. So, even if our reader is utterly unable to get rid of these caterpillars, there is a good chance the infested oak tree will survive.

The same can be said of the gypsy moth caterpillar, although repeated infestations can weaken a tree, leaving it susceptible to other insects or diseases. Gypsy moth caterpillars change in appearance as they mature. In the earlier stages of life, these caterpillars are only about a quarter of an inch long and are a brown and black color. As they grow longer (a fully grown caterpillar can grow to be as long as two and a half inches), they develop bumps and black hairs on their bodies. Like the tent caterpillars, gypsy moth caterpillars like hardwood trees, and especially delight in oak trees.

It is fairly clear that our reader is dealing with one of the two pests described above, but how should the infestation be dealt with? It is worth repeating that trees can be quite resilient in the face of infestation, with some trees being able to withstand a complete defoliation without perishing. So, our reader can take comfort in the fact that as annoying as these caterpillars can be (who wants to sweep their dead bodies off a driveway every morning?), there is a decent chance the affected oak will survive the infestation.

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Even so, there are measures that can be taken to address the infestation, regardless of whether the infestation is caused by tent caterpillars or gypsy moth caterpillars. Because we try to never recommend insecticides or other chemicals (although you can certainly find recommendations for these elsewhere on the web) we like something called a TreeHelp Bug Band, which is a protective roll that is wrapped around trees. These bands can keep caterpillars from reaching the foliage and can be used on infested and healthy trees.

3 Comments

  1. M. C. Reeves

    How long does this infestation last?

  2. Barbara Murray

    Have caterpillar ifestation on oak tree planted by builder when my house was built 5 years ago. Tree does well -is about 30 ft. tall but every year caterpillars come out of nowhere and eat every leaf on the tree within a day or two. I removed the 1st crop from tree and sprayed them with insect spray & removed all -trre looked ok-yesterday they all returned-small, medium & and large caterpillars. Not sure what kind they are – want to permanently remove from future infestation -what should I do?

  3. Dee

    I have little brown thick shells that appear on my oak leaves beginning late spring. The eventually hatch worms and leave poo on the terrace floor. how do I prevent this growth?

    Thank you

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