Relative Importance of Temperature-Acclimation and Stage in the Release of Sterile Flies for Population Suppression in Spring: a Pilot, Caged Experiment with Dacus Tryoni1

Abstract

Sterile-fly release experiments were conducted in controlled-environment cabinets intended to be analogous to releases for suppression of residual winter populations of Dacus tryoni (Froggatt) which are cold-acclimated and predominently immature at this time. Sterile flies (either cold-, or warm-acclimated) were caged with non-sterile, submature, cold-acclimated males and females. Temperatures fluctuated between successively higher daily maxima and minima as the experiments progressed so that in the 1st 2 weeks they only permitted maturation of immatures and only later did they permit mating. When mature sterile flies were used, both acclimation types were equally effective and suppressed the fertility of the target flies down to theoretically expected levels. Experiments that started with sterile tenerals (analogous to puparial releases) also revealed no differences between the 2 acclimation types, but in each case, fertility of the target flies was depressed significantly lower than theoretically expected levels. These results can be explained in terms of acclimation physiology and possibly by the relation of mating vigor to age.