INFLUENCE OF PREPUPATION ENVIRONMENT ON DIAPAUSE INDUCTION IN THE CARROT RUST FLY, PSILA ROSAE (FAB.) (DIPTERA: PSILIDAE)

Abstract

AbstractWhen carrot rust fly, Psila rosae (Fab.), collected as mature third-instar larvae on three dates in each fall of 3 years from carrots from the Holland Marsh, Ont., pupated in the laboratory at 10°C, the intensity of the diapause induced was lower in the samples collected latest in the season. Similarly, the latest pupating cohorts of pupae formed in the field exhibited less intense diapause and developed more rapidly at 20°C in the fall or the following spring. When larvae were kept at 1 or −2°C for varying periods before pupation at 10°C, the incidence and intensity of the pupal diapause decreased with increasing duration of exposure to the low temperatures. Larvae held at 5°C pupated in less than 60 days and entered diapause. Transfer of puparia from 20 to 10°C at various stages of pupation showed that diapause was induced if pupae were transferred less than 48 h after formation of the pupa was first evident.