Western Grapeleaf Skeletonizer
- 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
- 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.