Effect of temperature and humidity on the off-host survival of the wheat curl mite, Aceria tosichella

The wheat curl mite, Aceria tosichella Keifer, is an eriophyid pest of wheat, but its primary economic impact on wheat is through vectoring of viral pathogens that cause significant crop loss in winter wheat throughout the western Great Plains.  Temperature and humidity are among factors that often influence arthropod survival during dispersal from their hosts, yet the impact of these two factors on off-host survival is not known for A. tosichella.  Three distinct A. tosichella populations were subjected to five temperature regimes (10, 15, 20, 25 and 30°C) each at low and high humidity levels.  The mites were held singly in mini-chambers sealed using a thin Parafilm layer and placed in sealed plastic containers containing either Drierite  (1% RH) or a damp paper towel (95% RH).  Mites were held in growth chambers set at the target temperature, and monitored every 4 hours for 2 days, and thereafter, every 8 -12 hours until all had died.  Temperature and humidity but not mite population significantly affected off-host survival of A. tosichella.  Survival decreased with increasing temperature at both low humidity (38-40 hours at 10°C and 5 hours at 30°C) and high humidity (136-163 hours at 10°C and 20-27 hours at 30°C).  The results suggest that prevailing temperature and humidity conditions during A. tosichella dispersal will influence mite survival and establishment on new hosts.  Further studies under field conditions are needed to determine how temperature and humidity may influence mite movement from source plants to new hosts.