Southeast Michigan fruit regional report – September 10, 2012
We are finding record numbers of spotted wing Drosophila. Fall red raspberry growers must trap for this pest or check for infested fruit.
In the last four days (as of Monday, September 10), I have had a good number of phone calls and emails from fall red raspberry growers who are finding larvae or worms in fruit. In some cases, growers have discovered the fruit infestations themselves and many other growers have discovered wormy fruit when they have had calls from customers with wormy fruit.
In the last week, we have had record numbers of spotted wing Drosophila (SWD) caught at traps, indicating that pressure is building rapidly from this pest. Our small fruit entomologist at Michigan State University, Rufus Isaacs, is calling this the “SWD Tsunami.” This term is well said.
I also have had a good number of growers that have had a few adults caught in traps, but when they checked for infested fruit, have found a good number of fruit infested with larvae. This is what is so concerning to me!
If you have not been trapping for SWD, or checking for infested fruit, I am encouraging you to do so immediately. Here is some information on a simple technique for sampling for larvae in fruit using a fruit dunk flotation method. Collect a standard sample of fruit (maybe fruit for marketing, or suspicious fruit). Place the fruit in a plastic zip-lock bag and crush lightly to break the skin. Make a salt solution by dissolving 1 Tbsp. of salt in 1 cup of water and add this solution to the bag to cover the berries. After 30 minutes, examine the liquid to see if larvae are visible in the liquid. Larger SWD larvae will be visible as small, white pieces floating through the colored liquid. Placing this mix on a dark-colored tray is also an effective method for scoring the sample for SWD contamination. Detection of small larvae may require the use of a hand lens.
Isaacs has updated the publication Spotted Wing Drosophila Management Recommendations for Michigan Raspberry and Blackberry Growers. There is information in this guide on controlling this pest. The MSU IPM Spotted Wing Drosophila website also contains a great deal of other information on trapping and controlling SWD.