Experiments were conducted in commercial plantings of cabbage in spring 1994 and 1995 to evaluate the efficacy of a blend of pheromones for diamondback moth, Plutella xylostella (Linnaeus), and cabbage looper, Trichoplusia ni (Hübner), for disrupting mating when dispensed simultaneously from Yoto-con-S® ‘rope’ dispensers (Shin-Etsu Chemical Co., Ltd., Tokyo, Japan). A 12.1-ha cabbage field was treated with pheromone in 1994 using a blend of (Z)-11-hexadecenal, (Z)-11-hexadecen-l-ol acetate, and (Z)-11-hexadecanol in a 49:50:1 ratio for diamondback moth and (Z)-7-dodecen-l-ol acetate and (Z)-7-dodecen-l-ol in a 98:2 ratio for cabbage looper. The test was repeated in 1995 using a 10.1-ha cabbage field. In 1995, 24.6 ha of cabbage also were treated with a blend of diamondback moth-only pheromone: (Z)-11-hexadecenal and (Z)-11-hexadecen-l-ol acetate in a 50:50 ratio. All pheromone treatments were applied at the rate of 1,000 m rope per ha within 2 wk after the cabbage was planted. Captures of diamondback moth and cabbage looper males in traps baited with synthetic pheromones and mating by laboratory-reared sentinel females in pheromone-treated fields were significantly reduced for 7 to 9 wk post-treatment relative to control areas. Larval infestation data on cabbage were insufficient to establish the effect, if any, of the diamondback moth/cabbage looper combination pheromone treatment on cabbage looper control. In 1995, the diamondback moth pheromone only and the diamondback moth/cabbage looper combination pheromone effectively suppressed diamondback moth larval numbers below the composite economic action threshold of 0.3 larva per cabbage plant for approximately 60 days. A single application of pesticide quickly reduced the diamondback moth larval count below the action threshold in the pheromone-treated cabbage, and no further pesticide applications were required. The correspondent control field was sprayed 7 times with pesticides for control of diamondback moth.
