How to Manage Pests
UC Pest Management Guidelines
Scientific names: Drosophila melanogaster, D. simulans, and other species
In this Guideline:
DESCRIPTION OF THE PESTS
Various species of Drosophila are known as vinegar or pomace flies. In vineyards more than 95% are D. melanogaster and D. simulans. 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.
The spotted wing drosophila, D. suzukii, is a new exotic pest of California and has been reported to infest undamaged, soft-skinned fruits such as cherry, raspberry, blackberry, strawberry, and blueberry. The adult male spotted wing drosophila has a dark spot on the front edge near the tip of each forewing; the adult female looks the same as other Drosophila sp. commonly found in vineyards except that it has a large and serrated ovipositor. See MALE/FEMALE IDENTIFICATION CARD for more information on identification. Under laboratory conditions the spotted wing drosophila can be forced to infest grape berries, but under field conditions this has not been seen in California.
D. melanogaster and D. simulans are 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 drosophila flies 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. Pyrethrin and spinosyn insecticides can be used prior to and after harvest, but are not effective for long-term control as they only provide short-residual suppression of adults. In table grapes, note the presence of drosophila flies at harvest as an indicator of bunch rot diseases.
Monitoring and Treatment Decisions
No monitoring guidelines have been developed for Drosophila spp. in grapes. However, research conducted in cherries and other crops has shown that bucket style traps, containing apple cider vinegar or a yeast bait can capture spotted winged drosophila and other Drosophila sp. Do not use apple-cider-flavored distilled vinegar. The most successful traps are described in more detail in the 2014 Recommendations for Sweet Cherry .
UC IPM Pest Management Guidelines: Grape
Insects and Mites
L. G. Varela, UC IPM Program and UC Cooperative Extension, Sonoma County
Acknowledgment for contributions to Insects and Mites:M. C. Battany, UC Cooperative Extension, San Luis Obispo County
J. Granett, Entomology, UC Davis
P. A. Phillips, UC IPM Program, Ventura County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley