Learn to identify, monitor for new spotted wing drosophila fly

04/11/2011 04:07:00 PM
By Vicky Boyd, Editor

Although the spotted wing drosophila is now established throughout Florida, the good news is it has yet to cause economic crop damage.

Nevertheless, growers of small fruit should monitor for the pest when they have a crop to determine if it has made inroads and has begun to infest the crop. “Just stay aware, know when it’s there and be prepared to react,” says Jim Price, an entomologist at the University of Florida’s Gulf Coast Research and Education Center in Balm.

In addition, growers should learn to identify the spotted wing drosophila and how to differentiate it from the common but smaller Drosophila melanogaster that is found around rotting fruit, says Oscar Liburd, a UF associate entomology professor in Gainesville.

The good news, Liburd says, is the new pest can be controlled with an integrated program of monitoring, field sanitation and pesticides, if needed.

The spotted wing drosophila, a native of Japan, China and India, was first confirmed in the United States in California in 2008. Since then, it has spread and has been found in Kentucky, Michigan, Louisiana, Utah, South Carolina, North Carolina, Washington, Oregon and British Columbia.

The first specimens were trapped in Florida in August 2009 in Hillsborough County, and SWD has become established throughout much of the peninsula, Price says.

In Florida, the SWD could potentially infest strawberries, blackberries, raspberries, blueberries and stone fruit. Liburd says there’s a question about whether it also could potentially infest grapes and tomatoes.

The state’s growers have gone through two strawberry seasons and one blueberry season without economic damage, Price says.

Blueberry growers are entering their second season since the pest was first confirmed.

Affinity for ripening fruit

Unlike the common fruit fly that lays its eggs in rotting fruit, SWD prefers fruit just reaching maturity. Using a serrated ovipositor, the female cuts through the skin of fruit to lay eggs.

The opening also provides an entry way for rot-causing pathogens.

An average female can lay 300 to 400 eggs, Liburd says.

As the larvae develop, they eat the flesh, rendering the fruit unmarketable.

SWD is most active when temperatures average 68 to 69 degrees Fahrenheit, and adult activity falls off significantly when temperatures top 86 degrees.

“This might be good for Florida because I know in April and May the temperatures are much higher than that,” he says.

Based on trapping conducted between August 2009 and September 2010, Liburd says peak populations occurred in December and January. In 2010, another peak occurred in June and July.


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