Ministry of Agriculture
Operophtera bruceata (Hulst)
Mature Bruce spanworm larva
Bruce spanworm feeding damage to apple leaf and bud
Life Cycle: Overwinter as single eggs on twigs. Eggs begin to hatch at green tip and larvae present to petal fall. Spend summer in soil as pre-pupae; pupate in late summer. Adults present October and November when eggs are laid. One generation per year.
Monitoring: Examine host trees at tight cluster stage for larvae by visual examination or limb taps. Inspect fruit buds and leaves for signs of feeding damage.
Hosts: Fruit trees, willow, poplar, maple, alder
Comments: Bruce spanworm larvae resemble green fruitworm larvae, however spanwom larvae move by a characteristic looping movement and only have two pairs of prolegs (fleshy legs on abdomen) compared to five pairs for fruitworms.
Body length: Adult - 12.0mm; Mature larva - 18.0mm