Strong as an Oak: Trees should be OK against seasonal pest

By on August 17, 2016

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Summer is winding down, which means backpacks, No. 2 pencils, and the orangestriped oakworms are back! This native caterpillar is black with orange stripes and has two conspicuous horns near its head. Every year as we head into the last few weeks of summer, it makes itself and its appetite for tree leaves known.

They feed primarily on the leaves of oak trees but may also attack maple, hickory, cherry and hazelnut. When they are done feeding, the larvae drop from their host trees and wander around in search of a pupation site beneath soil. If their defoliation wasn’t already noticed, this is often the stage where they are found crawling on sidewalks, driveways or parking lots.

The orangestriped oakworm is often noticed on sidewalks, driveways, and parking lots as it searches for a pupation site (left image). They feed in clusters on oaks and other hardwoods, often resulting in localized and patchy defoliation of the tree (right image). Images by K. Oten, NCFS.

The orangestriped oakworm is often noticed on sidewalks, driveways, and parking lots as it searches for a pupation site (left image). They feed in clusters on oaks and other hardwoods, often resulting in localized and patchy defoliation of the tree (right image). Images by K. Oten, NCFS.

The good news is that because these insects feed on tree leaves late in the growing season, trees that are fed upon are easily able to recover and will re-leaf the following spring. The biggest concern is the aesthetic impact to yard and landscape trees. As caterpillars they feed in clusters, resulting in patches of missing leaves on an otherwise healthy-looking tree.

Because long-term tree health is usually not impacted, control efforts are usually not recommended. In addition, natural enemies such as birds, diseases and parasites may help to naturally lower the population. In some cases, pesticides can be used, but they are only effective when caterpillars are very small, and they may do more damage to the natural enemies themselves. By the time the caterpillars and their damage are noticed, it is usually too late for chemical control. If you wish to address concerns about your yard trees’ appearance, your best bet may be to hand-pick or shake the larvae from small trees.

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