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Orange-Striped Oakworm Diagnostic Guide

Anisota senatoria

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.

Birch

Hickory

Maple

Oak

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).
Orange Striped Oakworm Signs

Erich G. Vallery, USDA Forest Service – SRS-4552, Bugwood.org

Physical Appearance

  • 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.
Orange Striped Oakworm

USDA Forest Service – Northeastern Area Archive, USDA Forest Service, Bugwood.org

Biology

  • 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.

Treatment Strategy

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.

  • Soil Application using Lepitect

    Dosage: 0.2-0.4 oz/DBH”
    Timing: Apply two weeks prior to anticipated outbreak
    Re-Treatment: Re-applied 30 days after initial application if needed
    Lepitect
    Lepitect
    $59.20
  • Foliar Spray using Conserve

    Dosage: 6 fl. oz. / 100 gallons water
    Timing: Mid-August
    Re-Treatment: Every 4-7 days as caterpillars persist
    Conserve
    Conserve
    $136.08
  • Foliar Spray using Up-Star Gold

    Dosage: 10.8 fl. oz. / 100 gallons water
    Timing: Mid-August
    Re-Treatment: Every 7-14 days as caterpillars persist
    Up-Star Gold
    Up-Star Gold
    $33.33

Treatment Expectations

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

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