May 2, 2013

Spotted wing drosophila here to stay

The spotted wing drosophila (SWD) is now established throughout the United States. A native of Asia, the invasive pest of berries, stone fruit, grapes and other fruit crops made its first North American appearance in California in 2008. Since then, it has spread to most of the fruit-growing regions in the United States. As of 2012, it had been detected in 38 of the continental states, according to North Carolina State University (NCSU).

A common theme of SWD’s spread is a single detection, followed by intensive trapping, followed quickly by detection over a broad geographic range, according to Washington State University (WSU).

Like other vinegar flies, SWD appears to have a short life cycle (one to several weeks, depending on temperature) and may have as many as 10 generations per year. This rapid developmental rate allows it to quickly develop large populations and inflict severe damage to a crop, according to the University of California (UC).

SWD might be a relatively new pest, but it’s already caused “tens of millions of dollars in crop damage annually to cherries, raspberries, blackberries, blueberries and strawberries,” according to NCSU.

If the pest can’t be controlled, researchers estimate the losses could climb into the hundreds of millions of dollars. Some think SWD has the potential to destroy 40 percent of the blackberry and raspberry crops in the eastern United States, according to NCSU.

Common drosophila species will only attack damaged, overripe or dropped fruit, but SWD can attack undamaged fruit still on the tree, according to WSU.

Female SWD flies use serrated blades on the tips of their abdomens to cut through the skin of ripe fruit and lay their eggs. The eggs hatch into larvae that feed on the flesh of the fruit until they reach maturity – ruining the fruit in the process, according to NCSU.

Growers and researchers across the country are concerned about the increased use of pesticides, loss of income and greater input costs associated with SWD. They’re still searching for the best ways to manage the troublesome new pest.

For more information, read FGN's SWD Special Report.

– Matt Milkovich