There’s a New Bug in Town

by: Posted on: August 31, 2011

Photo: Bev Gerdeman

By Don McMoran, Agriculture and Natural Resources Extension Educator, WSU Skagit County Extension

Editor’s Note:  This article from Don introduces us to a new and potentially devastating pest for specialty crop growers, especially those cultivating small fruit.  He demonstrates how on the ground research by WSU professionals has shown that an in-depth understanding of a pest prior to reliance on chemical controls can lead to reduced costs for farmers by eliminating unnecessary pesticide applications, effective control through understanding the intricacies of the pest’s life cycle, and an approach that benefits all stakeholders while taking into account the Six Essentials we focus on here at Read The Dirt.


If you work with fruit you may have heard about a new insect that joined us in Western Washington back in 2009 called Drosophila Suzukii (Matsumura) Spotted Wing Drosophila or (SWD). This insect is Native to Southeast Asia and is believed to have been introduced to mainland America from Japan. This vinegar fly is related to the fruit flies that you may have seen in your home if you left your fruit out on the counter too long in the summer time.  The Spotted Wing Drosophila (SWD) thrives in the Japanese Maritime climate, which is very similar to that of the Pacific Northwest. The Spotted Wing Drosophila is an opportunistic pest which potentially infests various tree and small fruit. Damage by the insect is directed to intact ripening fruit, which include but are not limited to cherry, strawberry, blackberry, raspberry, blueberry, and grape. The SWD is 2-3 mm in length (about the size of the lead in a No. 2 pencil) and has been estimated to have between 6 and 8 reproductive generations in Western Washington per year. The female has a hack-saw-like structure on her abdomen that she uses to cut her way into ripening fruit to lay her offspring.  Once eggs are laid in the target fruit they hatch within 12 – 72 hours.  They can grow to adults in or outside of the infested fruit in 4 – 15 days. From there they take 20 – 30 days to become sexually mature. A single SWD fly can lay 350 + eggs in a lifetime so it doesn’t take many generations to completely overrun your fields.


In California, which represents the largest acreage of these fruits nationwide, SWD was responsible for an average of 20% crop loss, although near total infestations are possible.  Because of the significant threat SWD represents, a group of entomologists from California, Oregon, and Washington received a large USDA Specialty Crops Research Initiative (SCRI) grant to study its biology and management.  This project is headquartered at Oregon State University.


The Spotted Wing Drosophila is clearly establishing itself in Western Washington with increasing populations being seen in numerous small fruit. The risk of fruit damage and economic losses due to this new fruit pest continues to increase for any berry crop being harvested in the Northwest. It is highly recommended to take all appropriate measures to mitigate this risk.


The first step is to verify the presence of the invasive pest. WSU Extension has received funding from both the Washington Red Raspberry and the Washington Blueberry Commissions to educate and assist growers and homeowners with identifying the pest.  The majority of western Washington Extension offices have SWD trapping and monitoring programs in place.  These programs supply data to farmers, gardeners and to researchers.


To date there is no known biological control to combat the pest, although good sanitary practices such as picking up and disposing of any fallen fruit aids in keeping population numbers low. Luckily both commercial and organic pesticides have been found effective in control of the flies with the biggest question being about timing of sprays, as opposed to what to spray. Timing is critical due to exponential growth of populations in successive generations but integrated pest management has become a critical role in controlling the pest. “IPM is a sustainable approach to managing pests by combining biological, cultural, physical and chemical tools in a way that minimizes economic, health, and environmental risks.” This year the trapping programs have proven themselves effective.  Yes, there were SWD flies that were caught early in June but these were male flies; the female flies were found later in July but they were juvenile and unable to reproduce. It wasn’t until much later in August that Extension recommended applying a control. These efforts alone saved berry growers and homeowners thousands of dollars because only blueberry farmers were being threatened by SWD at that time in the growing season.  Reducing spray applications that in turn save farmers and homeowners money and reduce environmental impacts is just one way that WSU Extension is making your world a little bit better.  WSU- world class, face to face.


Six simple things you can do when dealing with pests: (Principles of IPM)

1) Know your pest- Not all insects are bad. Research the one that you are dealing with.

2) Monitor/Trap- Make sure the insect you suspect is causing damage is actually in your field/garden.

3) Establish Thresholds- How many pests are present before it is feasible to control them? Is one pest enough to apply a control or does it take thousands before your fruit/vegetables are unsellable?

4) Prevention- Are there cultural practices you can use to deter the pest?

5) Manage- Start with the most environmentally-friendly control methods before utilizing harsher chemical alternatives.

6) Evaluate- Did the system you use work effectively? If not start back over at #1.


If you get stuck, feel free to contact your local WSU Extension Educator. We have an office in every county in western Washington and we are here to serve you.




Don McMoran

Agriculture and Natural Resources Extension Educator

WSU Skagit County Extension



Skagit County Extension Spotted Wing Drosophila


Whatcom County Extension Spotted Wing Drosophila


WSU Extension SWD Update


You Tube Video


A research team, including scientists from California, Oregon, Washington and British Columbia are collaborating to understand the lifecycle of this pest as well as monitoring and management techniques.  The website,, has comprehensive reports and bulletins from all participating institutions.


Lynell Tanigoshi and his team at the Northwestern Research and Extension Center in Mount Vernon have posted information on their work on SWD at:


Peerbolt Crop Management is scouting fields in Oregon and Southwest Washington and is reporting data on their website:


WSU Whatcom County is scouting selected fields throughout the county for SWD.  See the map for results.  SWD Information for Homeowners

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