Description of the Pest
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 .
|Common name||Amount per acre**||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|MODE-OF-ACTION GROUP NUMBER1: 3A/—|
|COMMENTS: Spray containers with 1 pt/150 gal water and as needed. Apply to fruit in field, storage, or processing plants.|
|(Pyganic EC5.0II)||4.5–17 fl oz||12||0|
|MODE-OF-ACTION GROUP NUMBER1: 3A|
|COMMENTS: To protect honey bees, apply only during late evening, night, or early morning when bees are not present.|
|(Delegate WG)||3–5 oz||4||7|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: A stomach poison; most effective when ingested. Do not apply more than 19.5 oz/acre per crop per year or make applications less than 4 days apart. To protect honey bees, apply only during late evening, night, or early morning when bees are not present.|
|(Success)||4–8 fl oz||4||7|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|COMMENTS: Do not apply more than 7.5 oz/acre per crop per year. Labeled for the control of spotted wing drosophila. To protect honey bees, apply only during late evening, night, or early morning when bees are not present.|
|**||Apply with enough water to provide complete coverage.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI The longer of two intervals is the minimum time that must elapse before harvest.|