How to Manage Pests
UC Pest Management Guidelines
Various species of Drosophila are known as vinegar or pomace flies. Adults are small, yellowish flies and are commonly attracted to fermenting fruit of all kinds. Populations build up as the fruit harvest season progresses. The 0.25-inch-long maggot-shaped larva can be found in cull and damaged fruit in the vineyards. Oblong pupae occur wherever larvae are found and have a forked breathing tube at one end. The life cycle in summer is only 7 to 8 days, with the adult laying 700 to 800 eggs in a 20- to 30-day life span.
Vinegar fly is a problem of damaged or cracked fruit. Eggs are laid in damaged or exposed fleshy tissue and larvae feed on the berries. The primary damage by this pest, however, is the sour rot organisms that it vectors from bunch to bunch in the vineyard.
The key to controlling vinegar fly is to reduce the incidence of summer bunch rot. Good fertilizer and irrigation management and use of gibberellins (Thompson Seedless only) may reduce the number of tight bunches, thus decreasing the incidence of bunch rot. Good sanitation practices in storage or processing plants are helpful in reducing populations of this pest. Preharvest treatments are not effective; pyrethrin materials are used postharvest to kill adult flies. In table grapes, note the presence of vinegar flies at harvest as an indicator of bunch rot diseases.
UC IPM Pest Management Guidelines: Grape