Spotted Wing Drosophila (SWD)

Identification

Adult flies are brown, 2-3 mm long with red eyes and clear fly-like wings. Male flies have black spots on the end of each wing. Females have no spots but have a saw-like egg laying device (ovipositor) which enables them to cut into fruit and lay eggs inside.

Life Cycle

Spotted wing drosophila overwinters as adult flies. In spring, flies become active, mate and lay eggs in ripening fruit. A generation can take 8-21 days, depending on temperature. Up to 4 generations per year are expected in British Columbia.

Hosts

Numerous crops can be infested with SWD, including blueberry, raspberry, strawberry, blackberry, cherry, peach, and grape. Alternate non-crop hosts can include blackberry, other berries, and seedling cherry.

Damage

Unlike most small flies which infest decaying fruit, SWD females lay their eggs inside ripe fruit before harvest. Larvae hatch and begin to feed within the fruit, causing softening and fruit collapse. Contaminated fruit is unmarketable.

Management / Cultural Control:

• Alternate hosts near crop fields should be controlled or mowed to prevent fruiting.
• Remove or bury cull fruit. Keep equipment and processing areas free of old fruit.
• Good field care: decreases humidity in the field with adequate pruning and weed control.
• Be aware of host plants in adjacent fields and encourage neighbours to manage SWD.
• Overripe fruit is more likely to be infested with SWD. Pick early, clean and often.