News release: Spotted Wing Drosophila Returns

Tim Baker, MU Extension Horticulture Specialist
102 N. Main, Suite 1, Gallatin, MO 64640
660-663-3232, bakert@missouri.edu

Release Date: September 4, 2014

Headline: Spotted Wing Drosophila Returns

Last September, I wrote a column about a new insect pest of fruits, the Spotted Wing Drosophila (SWD).  This is a tiny fruit fly, which creates havoc by laying its eggs in fruits such as blackberries, raspberries, blueberries, cherries, and others. When the eggs hatch, the larvae eat their way through your fruit, ruining its quality.

My article also included a number of photographs of this pest, which I have included on my web site. If you think you have encountered a SWD, I would refer you to those photos so you can make a positive identification.

Last November, a meeting was held in Columbia about SWD, and what might be done to combat this pest.  One of the speakers was an entomologist from Michigan, where they have been battling this insect for several years. In short, it doesn’t look hopeful.

Yes, there are insecticides that can be used to kill SWD. Any insecticide program has to be a vigorous one to keep on top of things.  The SWD is so prolific, that you can’t afford to let it get the upper hand.

For organic growers, yes, there are organic-approved insecticides.  But there are not as many, and they are not as effective long-term as conventional materials. SWD is indeed bad news for organic growers.  Crops such as blueberries and brambles used to be an organic grower’s dream, with few pests to bother their crops.  Not anymore.  SWD has arrived.

It is possible that a few SWDs were around in 2012, but were not discovered.  2013 was our first real experience in Missouri with SWD, and the pest was encountered all over the state.

This year, reports started coming in by mid-June.  SWDs had survived the winter just fine, and were making their entrance for 2014.

I recently visited the farm where I took those SWD photos last year, and yes, the pest was around in high numbers again this year.  This was not a surprise, but certainly was a disappointment.

While last November’s meeting was not encouraging for growers, there are a few innovative approaches being tried.  One was exclusion. This would work well for high tunnels, if the pest were not already present. It used a very fine mesh screen, and the insects simply could not enter the high tunnel. This approach, however, would be relatively expensive, and thus anyone entertaining this idea would want to have a well-paying market that would help cover the cost of the structure.