Oak Leaf Skeletonizers: Scarlet Oak Sawfly Life Cycle and Control

Northwestern PA oak trees severely eaten by 1-inch white worms. Rural area.

Pest: Scarlet Oak Sawfly (Caliroa quercuscoccineae)

Also called oak slug sawfly (larvae covered in slime). Skeletonize leaves (leave vein network). Defoliation starts top crown, moves down. 2-3 generations/year.

Control Reality

• Insecticides: Orthene, Sevin, Dursban, malathion, diazinon on foliage.
• Large trees: Spraying impractical — can't reach canopy.
• Natural control: Predators usually crash population next year.
• Tree impact: Hardwoods withstand complete defoliation. Repeated years may reduce vigor.

Reference: Forest pests sawfly info