ECONOMIC THRESHOLD FOR 3 LEPIDOPTEROUS LARVAL PESTS OF FRESH-MARKET CABBAGE IN SOUTHEASTERN NEW-BRUNSWICK

Economic thresholds for the management of imported cabbageworm, Pieris rapae (L.), diamondback moth, Plutella xylostella (L.), larvae, and c abbage looper, Tricoplusia ni (Hubner), on cabbage, Brassica oleracea L., were evaluated at Bouctouche, New Brunswick, Canada, in 1992, 1993 , and 1995. Six treatments were tested in 1992: an untreated control; a weekly application of insecticide after insects appeared; a weekly a pplication of insecticide after heading; and an insecticide applicatio n when thresholds of 0.25, 0.50, or 1.0 cabbage looper equivalent per plant per week were reached. Eight treatments were tested in 1993 and 1995: an untreated control; a biweekly application of insecticide when insects appeared; a biweekly application of insecticide after heading ; and an insecticide application when thresholds of 0.10, 0.15, 0.20, 0.25, or 0.50 cabbage looper equivalent per plant per week were reache d. Generally, on average, for similar marketable yields, plots using t he 0.10 cabbage looper equivalent threshold needed 3 fewer insecticide applications compared with plots treated biweekly after insects appea red. In 1995, revenues for the 0.10 cabbage looper equivalent threshol d treatment were $9.49 per hectare greater than those for the biweekly treatments beginning after insects appeared.