DIAPAUSE STATUS OF THE OVERWINTERING GENERATION OF THE CARROT RUST FLY, PSILA ROSAE (FAB.) (DIPTERA: PSILIDAE), IN ONTARIO

Abstract

AbstractThe incidence of diapause in pupae of the second (overwintering) generation of the carrot rust fly, Psila rosae (Fab.), at the Holland Marsh, Ont., was determined at intervals during fall and spring of 1982–1983, 1984–1985, and 1985–1986, by placing pupae collected from carrot plantings at developmental temperatures in the laboratory. The percentage of samples in diapause increased with time of sampling from late September on, until 100% of the pupae collected in late November or early December were in diapause. The percentage in diapause of pupae overwintering in the ground of an insectary at Jordan Station, Ont., decreased from January onward until, by early April, diapause was virtually absent. In spring collections from the Holland Marsh, some evidence of diapause was detected in the earliest samples, indicating that diapause is a factor that should be considered when degree-day models are being developed for the carrot rust fly.