|Female SWD on raspberry at the Upper Mountain Research Station, Summer 2010. Photo: HJB|
While these classes of insecticides are effective against SWD, they come with risks as well. The key risk, from a pest management stand point, is non target impacts on other pests and beneficial insects. While we we cannot anticipate all of the non target impacts, some are clearly likely.
The most likely non target effect of SWD treatments is the possibility to flare spider mites.
|Twospotted spider mite female and eggs. Photo: HJB|
Strawberry, grape, and caneberry growers should scout their plantings for spider mites prior to beginning SWD treatments. A good rule of thumb is to observe at least 10 leaves or leaflets per acre or per variety block, if they are smaller than an acre. Spider mites can be observed and counted with a 10x hand lens. If spider mites are present, planting should be treated with a miticide before beginning organophosphate or pyrethroid treatments. North Carolina blueberry growers more commonly use these insecticides are rarely, if ever, have issues with spider mites, and I do not anticipate a need to manage mites in blueberries.
Spider mites may not be the only non target (unintentional) pest made worse by SWD treatments. Organophosphates and pyrethroids are broad spectrum materials, meaning they kill many different types of insects, including beneficial predators. The insects these predators may control could increase in their absence, but we cannot necessarily predict which insects these may be. Growers treating for SWD should be vigilant and scout their fields at least weekly to assess whether any new or unexpected insect or damage is present.