Pass the Fruit Salad, Please

Spotted wing drosophila on ripe fruit. Photo courtesy of homeorchardsociey.org.

A year ago I wrote about spotted winged Drosophila (SWD) in Oregon and the lessons learned from the first year of survey, management, and personal consumptive fruit sampling. Since then, another season has passed. We’ve got another year of experience and another belly-full of Oregon fruit under our belt, and we’re gaining confidence that SWD is not the nightmare we once feared.

In a nutshell, here is what we’ve learned from the perspective of growers, researchers, regulators, and consumers:

Growers

-Growers, including organic growers, can manage this pest if they pay attention and are ready to act when their crop starts ripening.

-SWD attacks ripe, soft fruit (especially raspberries, blackberries, and blueberries). It doesn’t bother green fruit or hard fruit like apples or pears.

-Populations are low in the spring and early summer. SWD builds up in late summer and fall. Numbers in the Columbia Gorge are consistently much lower than western Oregon.

-Grapes are not a preferred host. SWD is present in vineyards in the fall, but it seems to be attracted to split or damaged grapes.

Researchers

-There is a lot of research going on, and we understand this pest much better now than when it first showed up (http://groups.hort.oregonstate.edu/group/spotted-wing-drosophila), but there are still unanswered questions:

-Trap counts have increased dramatically in the fall the last two years. Thankfully, this is after our fruit crops are harvested, but we don’t understand why this happens. There were high trap counts all last winter, and then the population crashed in March. That’s weird. It would be nice to know what is going on.

-The standard trap (plastic cup with drilled holes) and lure (apple cider vinegar) is not very sensitive and it catches a lot of other non-pest Drosophila. It works for research, but it isn’t easy for growers/homeowners to use. We need a better trap.

-SWD is not hard to control, there are a number of materials that work, including organics, but with multiple generations, resistance could build up quickly. We need robust management strategies that don’t rely so heavily on cover sprays.

Regulators

-State and federal regulators across the country have decided not to enact quarantines for this pest recognizing they would have been impossible to enforce and consequently would have had a very low chance of success. Our decision in 2009 not to quarantine infested counties in Oregon was the right one.

-The Oregon Department of Agriculture (ODA) has worked with Oregon State University (OSU) and commercial crop consultants to make growers aware of this new challenge and management techniques they can use. The partnership has worked well.

Consumers

-There is plenty of fresh local fruit available. It is a good idea to rinse it before you eat it; it could have been sprayed, and reducing your exposure to pesticides makes sense.

-If you buy or pick fruit and some goes soft, pick out the bad ones and throw them away.

-Finally, if you’re into unsprayed fruit, accept that you could get some extra protein now and then in the form of SWD eggs/larvae. You won’t taste or feel them, and they aren’t harmful to ingest. 

I once asked another entomologist what he recommended for western cherry fruit fly (another pest with similar habits). He said, “Never eat half a cherry!” Our bodies are fine with the occasional swallowed insect, even if our mind says “gross.” In fact, insects are an important part of human diets in many parts of the world. Think about the choice of trace amounts of pesticide residues or a little extra protein. Which would you prefer to eat?  

Me? I choose fresh fruit from either conventional or organic sources and wash it, sort out any soft ones, and enjoy it. Works for me. During this season of thanksgiving, we should be thankful that we live in a fruit-producing state and have so much fresh produce available to us. Spotted wing Drosophila isn’t going to change that. “Pass the fruit salad, please.”

Dan Hilburn