Fly Taxonomy to Fly Trapping: A Tortuous Path to a Chemical Lure for the Spotted Wing Drosophila
Dr. Peter Landolt
Yakima Agricultural Research Laboratory
On June 12, 2012 at the Thad Cochran Southern Horticultural Laboratory in Poplarville, MS, Dr. Landolt presented on the topic of the new pest, Spotted Wing Drosophila (SWD). This insect has been in the United States for a few years, but is now spreading into Mississippi. Much of the research done on this pest has been done in Oregon and Michigan, where large acreages of multiple fruit crops were affected. SWD is a priority to consider because it is a threat to many soft fruits like blueberries, blackberries, strawberries, etc. The fly can oviposit into ripening fruit, pre-harvest instead of other fruit flies that just attack overripe fruit. There are numerous wild hosts for this fly and no known natural checks (predators) are in place at this time.
Much of the work Dr. Landolt has done is in the area of attractants and baits. These are used for detection of the insect and for monitoring of its presence in the field. Currently, baits are not optimized to catch the fly with as much specificity as is needed. Baits, as currently configured, do not catch enough flies, catch too many non-target flies, are messy, are not long-lasting, and provide inconsistent results. At present, the best lure is a wet trap containing a vinegar (2%; key component is acetic acid), wine (7%; key component is ethanol), and water mixture (remainder). Both vinegar and wine are attractants, but when used together are much more effective.
Unfortunately, right now not much is known about the SWD in our environment. Questions exist on how long they live, when they will attack fruit, where they come from, and how to control them. It is believed that the SWD can live year-round, feeding on wild host fruit and flower nectar even during the winter. They will not breed over the winter though, but will seek shelter in protected areas during cold spells.
The key to control is beginning a spray regimen. Three chemical pesticides are suggested for use: Imidan, Malathion, and Mustang Max. Imidan should be used only once and as the first spray since it has a long pre-harvest interval (PHI). Malathion and Mustang Max should be used in rotation and have a much shorter PHI (1 day). Scouting for the pest using traps will be a key component of when to begin sprays. The SWD prefers to attack fruit when color change in the berry occurs, so scouting should be set up prior to that.
Drs. Landolt, Sampson, and Adamczyk (all USDA-ARS) have put out traps in blueberry fields here in Mississippi to learn more about the presence of SWD and its timing. We will bring you updates on this pest as we learn more about it.
Oregon State University (http://horticulture.oregonstate.edu/group/spotted-wing-drosophila), Michigan State University (http://www.ipm.msu.edu/SWD.htm), UC-Davis (http://www.ipm.ucdavis.edu/EXOTIC/drosophila.html), USDA-APHIS (http://www.aphis.usda.gov/publications/plant_health/content/printable_version/Drosophila_Suzukii.pdf), Washington State University (http://www.tfrec.wsu.edu/pages/swd), University of Florida (http://entnemdept.ufl.edu/creatures/fruit/flies/drosophila_suzukii.htm), NC State (http://ncsmallfruitsipm.blogspot.com/p/spotted-wing-drosophila.html), and University of Arkansas (http://www.uaex.edu/Other_Areas/publications/PDF/FSA-7079.pdf) are sources of more information. I encourage you to access these websites and read the available information.
As updates become available, I will send them out to growers via email (mainly through the Gulf South Blueberry Growers Association), my blog (msfruitextension.wordpress.com), and in the Mississippi Vaccinium Journal (http://msucares.com/newsletters/vaccinium/index.html). If you wish to get the information directly from me via email please send your email address to me at firstname.lastname@example.org