Integrated Pest Management
Western Grapeleaf Skeletonizer
Harrisina metallica
Adult American grapeleaf skeletonizer (David Cappaert, Bugwood.org)
Western grapeleaf skeletonizer larva (Whitney Cranshaw, Colorado State University, Bugwood.org)
Western grapeleaf skeletonizer cocoon (Whitney Cranshaw, Colorado State University, Bugwood.org)
Pest Description
- adults: wingspan ~1 1/3 inches; blackish-metallic blue; wasplike
- larvae: ~ 5/8 inch; yellow, purple and black bands
- pupae: ~ 3/4 inch; flat, white silken cocoons
- eggs: translucent yellow; laid in groups
- in Utah, only an issue in the St. George area
Host Plants, Diet & Damage
- grape, Virginia creeper, Boston ivy
- young larvae feed in groups on the underside of leaves leaving the upper surface of the leaf intact
- late stage larvae skeletonize leaf tissue leaving large veins
- defoliation can lead to sun-damaged fruit
- feeding on grapes can lead to bunch rot
- spines on larvae can cause skin welts
Biology, Life Cycle & Damaging Life Stage
- overwinter as pupae in silken cases under bark or debris
- spring emergence coincides with leaf expansion
- eggs are laid in clusters of 10-200 on leaf undersides
- young larvae feed on leaves in groups, then feed singly in later stages
- two to three generations per year
- larvae are the damaging stage
IPM Recommendations
- Manage grapes to improve or maintain overall health.
- Monitor grapes for egg masses or larvae on the undersides of leaves after leaf expansion.
- Apply an insecticide (avermectin; Bacillus thuringiensis var. kurstaki; diamide; organophosphate; neonicitinoid; pyrethroid; spinosyn) to foliage when monitoring indicates small larvae are present.