Strawberry fruitfly
Drosophila melanogaster
(Diptera: Drosophilidae)

Description:

Fruit flies are small, yellowish flies that are commonly attracted to fermenting fruit of all kinds. Larvae are about 1/4 inch long and can be found in very ripe cull and damaged fruit in the fields.

Biology and damage:

Fruitflies are attracted to very ripe or damaged fruit in the field where they lay their eggs. They are primarily a problem in strawberries picked for freezing. Because this fruit is allowed to ripen in the field in order to allow easy removal of the strawberry calyx and core during picking, the harvest interval is increased and the fruit becomes more susceptible to infestation. Fruitfly eggs and larvae are primarily a contamination problem.
The life cycle in summer is approximately 7 to 8 days, with adults laying about 700 to 800 eggs in a 20- to 30-day life span (UC-Davis). Populations build up as temperatures become warmer. Ideal temperatures for development of this insect are in the low 80s F (27-30 C). The flies do not lay eggs at temperatures below 54 F (12 C) or above 91 F (33 C).

Field scouting/monitoring:

Although no monitoring or treatment guidelines exist for fruit flies in strawberries, yellow sticky cards can be used to monitor adult fly populations. Adults and their offspring may also be monitored using fermented fruit traps consisting of a container filled with overripe fruit covered with an inverted funnel.

Management:

CHEMICAL CONTROL
Chemical insecticides are not commonly used to treat for this pest. however, it may be possible to treat portions of fields or obvious sources of flies with pyrethrins to control adults.
California guidelines

CULTURAL CONTROL:
Limit breeding sites for fruit flies. Make certain that ripe fruit are completely removed from the plants. When possible, shorten harvest intervals as temperatures increase (UC-Davis). Practice good sanitation in and around the field. Identify and try to clean up external sources of flies such as cull piles of strawberries or other rotting fruit and nearby citrus groves where old fruit may be on the ground.