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Spotted Wing Drosophila Update -- 8/23/10:

Scouting for SWD is ongoing in a number of counties in Washington and Oregon. WSU Extension has maps with locations and numbers in Whatcom County and Skagit County. OSU and Peerbolt Crop Management are scouting in Clark, Cowlitz, and Lewis counties in Washington, and in Oregon Multnomah, Washington,Yamhill, Clackamas, Polk, Marion, Linn, Lane, Douglas, Jackson, and Josephine counties. Charts and tables show the progression of SWD trapping in each of those counties. Use these maps and charts as an overall indicator only.

The picture shows SWD larvae in a blackberry. Picture taken by Julie Pond.

Alert: Spotted Wing Drosophila, all berries: The risk of fruit damage and economic losses to this new fruit pest continue to increase. For any berry crop still harvesting in the Northwest, it is highly recommended to take all appropriate measures to mitigate this risk.

General Comments:
New Comments
• This week saw another geometric increase in overall SWD trap counts in the Oregon/SW Washington survey.
• The differences between fields treated with insecticides and non-treated fields and other areas also increased. With fields being treated seeing very low trap counts.
• There will be just one more weekly report week for the Oregon/SW Washington survey as the funding support for the field scouting from the state of Oregon only goes through the end of August.
• Some vineyard and late season caneberry and blueberry SWD trapping will continue through the end of September in these areas with scouts being funded through the Northwest Center for Small Fruits Research (USDA) grant.
• From an industry source--An alternative method for checking ripe fruit for SWD larvae infestation is to use one teaspoon of salt per one cup of water and to cover a fresh fruit sample in an open container with the solution. Within 5-7 minutes larvae are reported to emerge into the salt solution.
• This week, many more larvae are being recovered from wild Himalayan blackberry fruit than the previous week.
• There’s speculation within the industry that there seems to have been a ‘turning point’ around the latter part of July before which there were no major SWD larval issues and after which the population reached a point when larval contamination in untreated or undertreated fields became much more likely to be at economically damaging levels.
• Caneberries appear to be the preferred host although blueberries, strawberries, and other stone fruits and berries are also at high risk. If untreated caneberries (domestic or wild) are nearby, the risk to other crops is greatly increased.
Ongoing comments
• Some growers report finding larvae infested fruit even though they had little or no trap catches. The monitoring program for SWD is still very much a work in progress. There are many variables we’re still working out, so take this into consideration when making management decision.
• For machine harvesters, this is the time to assess the economic impact of having a lot of fruit on the ground and whether it’s necessary to invest more into research/methods of coping with this situation.
• This is also the window in time to evaluate the economic impact of Himalayan blackberries on SWD and whether it’s necessary to invest more into research/methods of coping with blackberries around the fields.
• Placing berries in a sealed baggie at room temperature with no liquid added is proving to be an easy monitoring technique for checking for SWD larvae. The larvae generally emerge from the fruit within a day of bagging. Warmth also encourages them to come out.
• As blueberry and caneberry fields finish harvest, a post harvest insecticide treatment is recommended to prevent the field from harboring a breeding population of SWD.