The western cherry fruit fly (Rhagoletis indifferens), often found in Washington and other areas in the Pacific Northwest, is a pest that has infested North American cherry orchards since the early 1900s. Even the smallest infestation can be extremely damaging to a cherry crop as the major commercial Washington markets have a zero tolerance policy and strictly control the movement of infected cherries to uninfected regions.
The adult western cherry fruit fly Washington is smaller than a regular house fly with a black body and white markings running in stripes across its abdomen. It can be easily distinguished from regular household flies and other fruit flies by the irregularly-shaped black markings on its clear wings.
These fruit flies have one generation per year. Females puncture the skin of the fruit to lay eggs within the pulp of the cherry. An average female may lay 200 eggs in one mating season. Once the larvae hatch, they begin to feed on the pulp until the fruit is fully ripened. At this point, the larvae fall to the ground and spend the winter pupating until early May when they emerge from the ground for two months during the cherry harvesting season.
Adults do little damage to the cherry themselves. The larvae are the real culprit. They feed on the pulp of the fruit as they grow and mature, leaving irreversible damage to the crop. There is a strict zero tolerance policy for cherry fruit flies in Washington State, because even the smallest infestation of this pest can destroy an entire season’s crop.
It is essential to use preventative measures when combating the cherry fruit fly, and to detect any infestation at the earliest possible stage. Yellow sticky traps can be placed in orchards in mid-May when flies begin to appear. If any flies are found, chemical sprays or alternate eco friendly solutions should be applied within that first week. The preventative sprays must cover the entire cherry and be highly concentrated in order to ward off adult flies before they are able to lay eggs inside the cherries. Sprays should be applied one or two more times throughout the season to ensure the infestation has been completely eradicated.