News & Press
They seemingly appear out of nowhere, silently marching on a singular mission. Almost overnight the damage becomes apparent. They’re creepy, they’re crawly, and they leave a wake of destruction in their path. It’s worse than the night of the living dead, it’s…CATERPOCALYPSE 2016!!!
Before you start dooms day prepping, let’s take a closer look at this tiny invader. The orangestriped oakworm is a native moth species that occurs throughout the eastern United States. It feeds mainly on oaks, preferring willow oak and pin oak, but occasionally feeds on other hardwoods as well. The rusty-orange moths emerge from the soil in June and July and lay their eggs on the undersides of oak leaves. In about a week, a tiny green caterpillar will hatch and begin to feed on the leaves. The caterpillars grow into larger black caterpillars with yellow or orange stripes running the length of its body. They also have a prominent pair of spines or horns sticking up behind their heads.
While the damage they inflict on the leaves looks horrific, it will not kill the tree. Let me repeat…IT WILL NOT KILL THE TREE. Orangstriped oakworms are considered late summer defoliators, and as such, their defoliation is less damaging to the health of trees than early spring defoliators. Trees at this time of year are done growing and are beginning the transition to their long winter’s sleep. They can afford to lose their leaves.
So why is the infestation so bad this year? One reason may be the mild winter we had. Since caterpillars burrow into the soil to pupate, the temperature of the soil during the winter plays a role in how many survive to emerge as moths in the spring. Freezing soil temperatures will kill many of the larvae. Population levels often rise and fall based on winter temperatures and predation by birds.
What can be done to stop this invasion? In most cases, treatment is not necessary. Again, it won’t kill the tree. It is best to rely on natural predators, such as birds, diseases, and parasites to control and lower the population next year. If treatment is warranted, such as protecting a small seedling oak or a high value tree, residents may spray their trees with Bacillus thuringiensis (Bt), Sevin or Orthene. Large trees will require a tree service company with equipment that can reach the upper branches.
Keep calm and know that Caterpocalypse is short-lived and won’t decimate all the oak trees in town. Just be glad it isn’t Gypsy moth.
by Jennifer Rall, Urban Forestry Coordinator
Town of Wake Forest
Here is a link for info on the orangestriped oakworm from NCSU Dept. of Entomology. It has a good description of the caterpillar and also provides info on treatment.
Find an arborist: http://www.treesaregood.org/findanarborist/arboristsearch.aspx