D. suzukii was lower in 2011, based on capture of adults in traps and adults reared out of fruit, while pressure in the following year was earlier and much higher. Winter temperature conditions are expected to limit D. suzukii populations (Dalton et al., 2011), and the observed annual variation may have been a result of the unusually mild 2011e2012 winter characterized by limited periods of very cold temperatures. For example, the winter before this study(2010e2011) the minimum winter air temperature recorded at the TNRC was 24.7 C compared to 15 C in the 2011e2012 winter.
Additionally, at this site the two winters had twelve vs. four days of 10 C or less, respectively. The observed changes in fly populations from year to year present difficulties in preparing management plans for this pest, especially when efficient and costeffective IPM tools are lacking, but winter conditions may ultimately be used to provide a risk ranking for the coming season’slevel of pest pressure from D. suzukii. In higher pressure years where D. suzukii populations increase earlier in the season, effective control will require more sprays and tighter spray intervals than years where population increases are delayed. In addition, the amount and timing of rainfall will impact the effectiveness of insecticides and the need for re-application to keep fruit protected.
The development of reliable trapping (Lee et al., 2013) and larval detection techniques will aid growers, scouts, and extension agents in determining the timing and magnitude of thepest population,and the performance of control programs.