Lethal Effects of Suboptimal Temperatures on Immature Stages of Anastrepha Suspensa

Abstract

Immature stages of Anastrepha suspensa (Loew) (Diptera: Tephritidae) were exposed for variable periods of time to temperatures ranging from 1.7 to 15.6 @*C. Lethal effects varied inversely with temperature. Regression equations were calculated and LT"5"0 and LT"9"5 values (lethal time for 50% and 95% mortality) are presented. Data points for all stages showed high linearity when percentage mortalities were converted to probits and plotted against log-days (exposure time), providing correlation coefficients within the range of 0.934-0.999. Susceptibility to cold decreased with the age of the eggs at the temperatures and exposure periods tested. Less than 50% of mature larvae were killed from exposure to 15.6 @*C for 28 days, but 7.2 @*C for 7 days produced 99.8% mortality. Exposure to 15.6 @*C had essentially no lethal effect on pupae and 12.8 @*C for 28 days killed only 45.4% of them. Two-day-old pupae were more sensitive than older groups exposed to 4.4 @*C. By comparison, mortality of 2-day-old pupae exposed to this temperature for 3 days was 99.8% while mortality of 10-day-old pupae exposed for 15 days was 99.9%. The order of susceptibility (LT"9"5) of immature stages of A. suspensa exposed to 7.2 @*C was larvae > eggs > pupae.