A Sex Attractant Synergist for Trichoplusia oxygramma (Lepidoptera: Noctuidae)

Abstract

Trichoplusia oxygramma (Geyer) is closely related to the cabbage looper, Trichoplusia ni (Hubner), although it is not a pest species. Like many other Plusiinae, males are attracted in the field to traps baited with (Z)-7-dodecen-1-ol acetate (Z7-12:Ac), the major component of the sex pheromone of the female cabbage looper (Mitchell et al. 1972). During an experiment in which traps were baited with combinations of female cabbage looper sex pheromone components, T. oxygramma males were caught in traps baited with a combination of Z7-12:Ac and (Z)-9-tetradecen-1-ol acetate (Z9-14:Ac). We report here the result of a subsequent experiment demonstrating an increased sex attractant response by T. oxygramma males to Z7-12:Ac plus Z9-14:Ac compared to Z7-as:Ac alone, as indicated by trap catches. Plastic bucket traps (Universal moth trap, International Pheromones, Merseyside, England) were baited with two lures; a 1-mg dosage of Z7-12:Ac or a combination of 1-mg Z7-12:Ac and 90 ,ug Z9-14:Ac on a rubber septum. This ratio of 10 to 0.9 for Z7-12:Ac to Z9-14:Ac approximates the ratio of those components reported by Bjostad et al. (1984) for the female cabbage looper pheromone and is similar to the ratio in our original experiment in which T. oxygramma males were trapped. Septa were pre-extracted, handled and loaded as described by Landolt and Heath (1986). Traps were hung from shrubs about 1 m above ground level in uncultivated fields near Gainesville, Florida during Sept. and Oct. 1985. Traps were positioned as four treatment pairs with about 24m between paired traps. These were checked and septa switched daily between paired traps. Septa were replaced after 1 week. Treatment means were separated by Student's t-test at p > 0.05. Mean numbers of male T. oxygramma caught per week in traps baited with Z7-12:Ac plus Z9-14:Ac were significantly higher than in traps baited with Z7-12:Ac alone (Table 1), indicating a synergistic effect by Z9-14:Ac on the attractant response of male T. oxygramma to Z7-12:Ac. Although (Z)-9-14:Ac is a minor component of the sex pheromone of female T. ni (Bjostad et al. 1984), it did not have any synergistic effects on the response of T. ni males to Z7-as:Ac in a wind tunnel bioassay (Linn et al. 1984). Landolt and Heath (1986) also reported that numbers of male P. includens caught in traps were reduced greatly by the addition of Z9-14:Ac to Z7-12:Ac, indicating an inhibitory effect which may function in preventing interspecific courtship and mating between Trichoplusia spp. and P. includens. (Z)-9-Tetradecen-1-ol acetate also inhibits the attractant response (reduced trap catches) of two other species of Plusiinae, Autographa californica (Speyer) and A. flagellum (Walker), to Z7-12:Ac (Steck et al. 1979). Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.