Orange-Striped Oakworm Diagnostic Guide
Orange-striped oakworm, Anisota senatoria, is found primarily on oak trees and other hardwoods in late August and September. This insect is active primarily in the Eastern US, and is more of a nuisance than a pest. Larvae can defoliate an entire tree and rain down excrement, known as frass. This happens late in the season and does little harm to the tree, but can be a nuisance when the excrement covers patios, driveways, and sidewalks.
This pest attacks mostly oak but also maple, hickory, and birch.
Signs of Damage
- Leaves are completely consumed, leaving only the midrib.
- Twig dieback in small trees.
- Defoliation of entire tree.
- Frass can be seen, and in some cases, frass can be heard falling from tree(s).
- Caterpillars that are 1.5 to 2 inches long, black, and have several narrow yellow-orange lines running the length of the body. Behind the heads are stiff blunt spines.
- Overwintering occurs in the ground as a pupa.
- Adult moths emerge between June and August and lay eggs in clusters on the underside of leaves.
- Larvae are active and feeding from July to August.
- Larvae drop to the ground in August or September and burrow into the soil to pupate.
Management of orange striped oakworm is not strictly necessary for two reasons: first, the pest does most of its damage late in the year. As most trees have completed growth by that point, it matters little if the tree is defoliated. Second, natural predators are very effective against the caterpillar. Birds, other insects, and bacteria all naturally feed on or in this pest. Caterpillars may also be shaken to the ground by shaking small trees or shaking limbs with a pole or rope. If chemical treatments are warranted, young larvae should be targeted because they are more susceptible to insecticides than mature larvae. Look for defoliated branch tips beginning in mid-August.
Conserve™ has a short residual of 4 to 7 days but is softer on beneficial insects, whereas Up Star Gold™ will provide slightly longer residual, but is broad spectrum.
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org