Spotted Wing Drosophila (SWD) is a vinegar gnat from China and Japan. It attacks ripening and ripe fruit of brambles (raspberry & blackberry), strawberry, blueberry, grape, cherry, plum and peach, plus many species of wild berries. We first discovered it in New Hampshire on September 6, 2011. In 2012, SWD caused over $1.5 million in crop losses in NH. If you wish to keep your fruit from becoming infested, it is critical to monitor the insect with traps. When the flies appear and your crop is ripening, an insecticide spray can prevent it from being infested. Other cultural practices are important, like frequent harvesting during periods of high risk and refrigerating fruit after harvest.
In general, SWD adult flies are not detected in traps in NH until early July. The exact timing varies from year to year and site to site.
Trapping at your own farm is the best way of knowing what is happening in your crop and will help you make the most effective management decisions. Watch this page for alerts of population spikes and other notable events that may affect your management decisions.
***SWD do not lay their eggs during periods of high heat, so evening temperatures above 80°F mean very low risk of infestation***
UNH Cooperative Extension’s crop insect monitoring programs are made possible through support from the NH Department of Agriculture, Markets and Food’s IPM grant program.