SEASONAL ACTIVITY OF ADULT CARROT RUST FLIES, PSILA ROSAE (DIPTERA: PSILIDAE), IN THE LOWER FRASER VALLEY, BRITISH COLUMBIA

Abstract

AbstractMean weekly catch of adult Psila rosae (F.) on sticky, yellow-painted cardboard traps from 93 commercial carrot fields provided seasonal records of their activity during 1980–1983 in the lower Fraser Valley, British Columbia. When monitoring extended from April through November in 1982 and 1983, 3 distinct periods of adult activity were observed that probably reflect the occurrence of 3 adult generations per year. Trap catch first peaked in mid- to late-May, followed by a second peak in late-July to early-August, and a third peak in mid-October. Of the temperature summations calculated, those commencing 1 February provided the most accurate degree-day (DD) indices for predicting seasonal activity of overwintering and 1st-generation adults. Four-year means for cumulative DD above 3 °C (air temperature) after 1 February for first, 10%, maximum, and 90% trap catch of the overwintering generation were 326, 435, 557, and 838 DD, respectively.