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.
Damage
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.
Management
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 .
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(fish) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
PyGanic EC 5.0 II # | Postharvest | 7 |
3A |
4.5–17 fl oz | 12 | 0 | To protect honey bees, apply only during... | broad | — | moderate | moderate | short | low | low | high | very low | intermediate | 07/2015 | ||
|
|
various products | Postharvest | 7 |
3A/— |
Label rates | 12 | 0 | Spray containers with 1 pint per 150 gal... | broad | — | — | — | short | — | — | — | — | — | 07/2015 | ||
|
|
Delegate WG | Postharvest | 7 |
5 |
3–5 oz | 4 | 7 | A stomach poison; most effective when in... | narrow | low/moderate | moderate 13 | moderate/high | moderate 14 | low | low | low | very low | low | 07/2015 | ||
|
|
Entrust # | Postharvest | 7 |
5 |
1.25–2.5 oz | 4 | 7 | Do not apply more than 7.5 ounces per ac... | narrow | low | moderate 13 | low/moderate | short | very low | low | low | very low | low | 07/2015 | ||
|
|
Success | Postharvest | 7 |
5 |
4–8 fl oz | 4 | 7 | Labeled for the control of spotted wing... | narrow | low | moderate 13 | low/moderate | short | very low | low | low | very low | low | 07/2015 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- # a b Acceptable for use on certified organic crops. Check with your certifier to confirm before application.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. Rotate pesticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
- 13 a b c Toxic to some natural enemies (lacewing and syrphid fly larvae, predatory beetles, and thrips) when sprayed and up to 5 to 7 days after.
- 14 ↩ Residual is moderate if solution is between a pH of 7 and 8.
UC IPM Pest Management Guidelines: Grape
UC ANR Publication 3448
L.G. Varela (emeritus), UC IPM and UC Cooperative Extension Sonoma County
D.R. Haviland, UC IPM and UC Cooperative Extension Kern County
W.J. Bentley (emeritus), UC IPM and Kearney Agricultural Research and Extension Center, Parlier
L.J. Bettiga, UC Cooperative Extension Monterey County
K.M. Daane (emeritus), Kearney Agricultural Research and Extension Center, Parlier
R.J. Smith (emeritus), UC Cooperative Extension Sonoma County
L.R. Wunderlich, UC Cooperative Extension Central Sierra
F.G. Zalom (emeritus), Entomology, UC Davis
Acknowledgement for Contributions to Invertebrates
M.C. Battany, UC Cooperative Extension San Luis Obispo County
J. Granett (emeritus), Entomology, UC Davis
P.A. Phillips (emeritus), UC Cooperative Extension Ventura County
A.H. Purcell (emeritus), Environmental Science, Policy, and Management, UC Berkeley
