APPLICATION OF THE CABBAGE LOOPER EQUIVALENT MODEL TO LEPIDOPTEROUS PESTS OF BRUSSELS SPROUTS IN PRINCE EDWARD ISLAND

AbstractAn investigation into the use of thresholds based on Cabbage Looper Equivalents (CLE) was conducted on Brussels sprouts, Brassica oleracea var. gemmifera (L.), cv. Valiant, grown in Prince Edward Island in 1991 and 1992. The CLE model was used to equate foliage consumption by larvae of the imported cabbageworm, Pieris rapae (L.), the diamondback moth, Plutella xylostella (L.), and the cabbage looper, Trichoplusia ni (Hübner). Management strategies included the following: (1) an untreated check; applications of insecticides after thresholds of (2) 1.0 CLE; (3) 0.50 CLE; or (4) 0.25 CLE per plant were exceeded; (5) bi-weekly applications of insecticides; and (6) applications of insecticides according to the grower’s spray schedule.In 1991, the imported cabbageworm was the most abundant species in the complex attacking the crop and high yields were obtained in all treatments. However, in 1992, the diamondback moth was the principal species and significantly reduced marketable yields in all treatments. Use of CLE as a model for threshold determination in the crop of Brussels sprouts underestimated the potential of the diamondback moth for damage and resulted in improper timing of applications of insecticide for adequate control of the diamondback moth.