Thursday, July 8, 2010

Spotted Winged Drosophila is Spotty Alright

Years ago, an entomologist in Washington State coined the term POTY for pest of the year. It does seem like some new invasive pest shows up every year in the Pacific Northwest. The POTY of 2009 was spotted wing Drosophila, Drosophila suzukii. This year, Oregon’s fruit growers are learning to live with this new pest.

Spotted wing Drosophila is an Asian species first detected in California in 2008. Last summer it appeared suddenly in the Pacific Northwest and caused some damage to late-season caneberries and peaches. Since then, it has also been detected in Florida and South Carolina.

Regulators like myself were slow to recognize the threat. Most species of Drosophila (vinegar flies, small fruit flies) are not pests. The little guys that fly around your over ripe bananas are a good example. They lay their eggs in rotten fruit that is already past its prime. Who cares? Spotted wing Drosophila is different. Females have “large” ovipositors (egg-laying apparatus barely visible to the naked 50+ year-old eye) that can saw through the skin of ripe fruit before it gets soft.

Last year, we learned that fruit could look great right up until harvest, and then be ruined by spotted wing Drosophila. This year, Oregon State University Extension has been preparing growers and working out management strategies to protect their fruit ( In addition, Peerbolt Consulting and OSU are monitoring over 500 traps to track population trends in the state (

With strawberry harvest behind us, and cherry, raspberry, and blueberry harvest underway, there have not been any reports of crop loses from this new pest so far. Here is a summary of what we’ve learned:

·         There are lots of other species of Drosophila out there, and they all look alike.
·         Commercial growers, including organic growers, have been able manage spotted wing Drosophila populations when necessary.
·         Spotted wing Drosophila is widespread in Oregon, but the distribution is spotty.
·         Here and there, backyard growers have reported more soft fruit than usual, and in some cases, spotted wing Drosophila was the culprit.

We don’t know why some sites have more spotted wing Drosophila than others. I have fruit trees and berry bushes in my yard. Spotted wing Drosophila has not shown up, but three other species of fruit flies are hanging around. I don’t spray my trees, and so far the fruit has been delicious with no Drosophila aftertaste.

It is still too early to know how spotted wing Drosophila will affect late season fruit, but indications are that Oregon’s fruit growers are not going to be put out of business by last year’s POTY. The rest of us are unlikely to notice any changes. The fruit that is reaching the market is high quality and delicious. It is another invasive pest, but it’s manageable, thank goodness.

New pest introductions are a price we pay for having fresh produce from far away places available year around in our supermarkets. I wonder what the POTY of 2010 will be?

Dan Hilburn

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