MATING DISRUPTION OF DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE) IN CABBAGE - REDUCTION OF MATING AND SUPPRESSION OF LARVAL POPULATIONS

An 8.1-ha field of and-wk-old cabbage within an area of general cabbage production received a single treatment with 8100 m of a continuous-rope formulation of a 70:30 mixture of (Z)-11-hexadecenal and (Z)-11-hexadecen-1-ol acetate, two components of the sex pheromone of the female diamondback moth, Plutella xylostella (L.). Captures of males in synthetic pheromone-baited traps, mating of laboratory-reared sentinel females, and the mated status of native moths taken from the plots demonstrated suppression of mating activity by the pheromone treatment relative to that in the control area for 9 wk. Cabbage in this farm was planted sequentially. Fifteen insecticide treatments were applied during production of the block of cabbage, planted 13 d before the pheromone-treated cabbage, and 13 applications were made to the adjacent (control) block of cabbage planted 3 d after that in the pheromone plot. Two insecticide treatments were applied to plants in the pheromone-treated block to control diamondback moth larvae resident at the time of the pheromone application, and one spray was applied to this block 10 wk later at harvest. Cabbage at the extreme perimeter of the pheromone-treated area was damaged heavily by diamondback larvae; however, larval and pupal counts throughout most of this plot remained comparable to those in the control area. Cabbage at the interior of the pheromone area was graded as U.S. no. 1 quality. The results indicate that mating disruption can be used to protect cabbage from diamondback moth if pheromones are applied to areas of at least 8.1 ha with some supplemental application of insecticide.