vinegar fly
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Beginner
Scientific Name
Various species of Drosophila
Identification
Adults
- Small, yellowish flies
- 0.25-inch-long maggot-shaped
- Oblong with a forked breathing tube at one end
Injury
- Don’t injure the fruit directly but help spread bunch rot from infected to uninfected bunches
Often Confused With
Grape berry moth injury: no webbing in cluster and no frass inside berries
Period of Activity
Pre-harvest.
Scouting Notes
As fruit ripen, look for clouds of adults and maggots feeding in injured fruit. Frequently found where bunch rots have occurred.
Threshold
None.
Advanced
Scientific Name
Various species of Drosophila
Identification
Adults
- Small, yellowish flies
- 0.25-inch-long maggot-shaped
- Oblong with a forked breathing tube at one end
Injury
- Don’t injure the fruit directly but help spread bunch rot from infected to uninfected bunches
Often Confused With
Grape berry moth injury: no webbing in cluster and no frass inside berries
Biology
Adult vinegar flies have a life span of 20 to 30 days and can lay 700 to 800 eggs during that time. They lay their eggs on injured fruit. The eggs hatch and larvae enter the berries and feed on the flesh. When mature, the larvae pupate in the grapes and hatch to produce adults.
Vinegar flies are attracted to volatile compounds produced by injured berries, especially those infected with Botrytis bunch rot and sour rot. As grape berries ripen, they may pull away from their stems, especially when clusters are tight. This exposes the fleshy part of the fruit and is an attractive spot for vinegar flies to lay eggs. Vinegar flies will also progress from earlier to later-ripening varieties through the harvest season.
Period of Activity
Pre-harvest.
Scouting Notes
As fruit ripen, look for clouds of adults and maggots feeding in injured fruit. Frequently found where bunch rots have occurred.
Threshold
None.
Management Notes
Minimize injury to the berries, especially bunch rots. Remove thinned fruit from the vineyard or incorporate it by cultivation. Preharvest insecticide treatments are not effective.
