Crop Profile for Cherries (Sweet) - Regional IPM Centers

Insect Pests
WESTERN CHERRY FRUIT FLY
Rhagoletis indifferens (Curran)
Western cherry fruit fly is native to North America and has been found in the Pacific Northwest states
since the 1940s. Even though it does very little actual damage to commercial fruit and is rarely found in
commercial orchards, it is the most important pest of sweet cherries in Washington because of
quarantine restrictions. Quarantine agreements with California and export market countries carry a zero
tolerance for cherry fruit fly larvae in packed fruit. Washington State Department of Agriculture
(WSDA) inspectors are stationed at each cherry packing facility during the harvest season to check fruit
for infestation as it comes to the packinghouse, prior to acceptance, and again after packing. Fruit is
rarely found to be infested. However, single larvae are found during inspections of fruit produced in
Washington State’s sweet cherries from five to twenty times per season. When a larva is found, the
entire load of infested fruit is rejected, and all other fruit from that grower is intensively inspected for
signs of cherry fruit fly. While native cherry species have been reported as hosts, it is uncommon to find
this pest on any tree other than sweet or tart cherry.
Control
Scouting/Predictive Models
The zero quarantine tolerance for cherry fruit fly has forced growers into intensive control programs to
achieve perfect control. Commercial growers begin spraying when first fly emergence is detected by
advisors on infested sentinel trees or when temperature-driven phenology models (Jones, et al., 1991)
indicate emergence has commenced in the region. The phenology model has predicted first trap catch of
adults on heavily infested trees very accurately during eight seasons of use in Washington State. Once
growers commence spraying for cherry fruit fly control, they continue to spray every week to ten days,