Researchers, growers continue to gain insight into the spotted wing drosophila fly

05/01/2011 10:40:00 AM
By Vicky Boyd, Editor

Tweaking the recommendations

The University of California published in January what it is referring to as provisional management guidelines for this cherry season.

They can be viewed at http://bit.ly/i8hjMW.

Oregon State University’s 2011 recommendations are available at http://bitly.com/ek2HrZ, and Washington State University’s are at http://bit.ly/enZU3B.

“The treatments have been tweaked based on what we found works better and to take stock of some MRL restrictions on some materials,” Grant says of the UC guidelines.

For example, UC guidelines now recommend beginning treatment when the earliest varieties in the orchard—which may be pollinizers—are straw colored rather than green.

“It appears that the fruit really doesn’t become attractive to egg laying until it’s at least yellow in color,” Grant says.

That recommendation was based on results of earlier laboratory tests conducted by Oregon State University. Van Steenwyk says researchers will conduct field trials with caged flies this season to see if that is indeed true.

Preliminary research also has shown varietal differences in susceptibility, with fruit that matures early and is soft at maturity being more susceptible, Van Steenwyk says. Therefore, Early Burlat is more susceptible than Black Tartarian, which is more susceptible than Bing.

Once the fruit enters the susceptible stage and flies are present, growers should begin treatments and continue them on seven- to 14-day intervals, depending on label recommendations, through harvest.

The UC guidelines also warn growers to play close attention to treatment re-entry and pre-harvest intervals as harvest nears.

In eastern Washington, SWD control can be integrated into a cherry fruit fly program because many of the materials that control SWD also control the cherry fruit fly. But the reverse isn’t always true, according to Extension recommendations.

Taking a hard look at control

Joe Valente, who grows cherries near Lodi, Calif., says he hasn’t had a real problem with SWD.

Most of his crop had already been picked when the fly first started causing significant damage to California’s Central Valley cherry crop in Valley in 2009. Because of the damage that some growers reported in 2009, Valente says he adopted an aggressive spray program in 2010.



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