Effect of humidity on developmental parameters and field catches of Drosophila suzukii

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is an invasive species initially detected in 2009 in Oregon.  It is a known global pest on small and stone fruits.  Previous lab work has determined the role of temperature on the rate of development, however the role of humidity is unknown.    While monitoring for D. suzukii in blueberries grown in the Willamette Valley over the past four years, fly numbers across the field would consistently vary.  During the 2012 and 2013 field season, data loggers were deployed in different areas on an organic blueberry production unit to track temperature and humidity in conjunction with the capture of flies in apple cider vinegar traps.  Concurrently, eggs and adults were exposed to five different relative humidity levels under controlled laboratory conditions.  Developmental period, longevity, and fecundity were recorded to determine the effect of humidity for these parameters.  Results from these experiments have significant impacts on these parameters, with low humidity being the limiting factor.   The importance of humidity as a factor for D. suzukii population growth rate will be illustrated.