Identification of the Sex Pheromone of the Pink Grass Worm, Tmetolophota atristriga, Reveals Possible Population Differences in Male Response to Sex Pheromone

The pink grass worm, Tmetolophota atristriga (Walker), is an endemic New Zealand noctuid moth species that is abundant throughout the North and South Islands. The larvae are minor defoliators of agricultural pasture. We investigated the sex pheromone of this species. Analysis of extract of the female sex pheromone gland identified six compounds: two monounsaturated compounds, (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-11-hexadecenyl acetate (Z11-16:Ac), three saturated compounds, hexadecanal (16:Ald), hexadecyl acetate (16:Ac) and octadecan-1-ol (18:OH), and a triene hydrocarbon, (3Z,6Z,9Z)-tricosatriene (Z3Z6Z9-23:Hy). Several field-trapping experiments testing combinations of the six compounds were conducted. Results suggested that males of two different populations of T. atristriga responded differently to different blends of the compounds. Males of one population responded equally to a two-component blend as to other blends, including the one with all six compounds. By contrast, males of the second population responded only to the six-component blend or a ternary blend of Z11-16:Ald, Z11-16:Ac and Z3Z6Z9-23:Hy. In experiments testing different doses of Z11-16:Ald and Z11-16:Ac in a binary or a six-component blend, a 1 mg dose of the binary blend gave the greatest male catch for both populations. This is the second sex pheromone identification of a New Zealand species of Noctuidae and is the first reported occurrence of Z3Z6Z9-23:Hy as a sex pheromone component of any noctuid species.