Identification of the sex pheromone of the pink grass worm, Tmetolophota atristriga, reveals two different taxa

The pink grass worm, Tmetolophota atristriga (Walker), is a New Zealand native species. It is abundant throughout the North and South Islands and is a pest which defoliates pasture. In this study, the sex pheromone of this species was investigated. Analysis of the extract of the female sex pheromone gland by GC/EAD, GC/MS and chemical derivatization identified six compounds: two monounsaturated compounds, (Z11)-hexadecenal (Z11-16:Ald) and (Z11)-hexadecenyl acetate (Z11-16:Ac), three saturated compounds, hexadecanal (16:Ald), hexadecyl acetate (16:Ac), octadecan-1-ol (18:OH), and a triene hydrocarbon, (3Z,6Z,9Z)-tricosatriene (Z3Z6Z9-23:Hy). Several field trapping experiments were conducted testing various pheromone blend combinations of the six identified compounds. Results suggested that the two different taxa of T. atristriga respond differently to the female sex pheromone compounds. The first taxon responds equally to the two-component and other blends including the six-component blend. The second taxon responds only to the six-component blend containing Z11-16:Ald, Z11-16:Ac, 16:Ac, 16:Ald, 18:Ald and Z3Z6Z9-23:Hy or a ternary blend containing Z11-16:Ald, Z11-16:Ac and Z3Z6Z9-23:Hy. In experiments testing various doses (0.1, 1, and 10 mg) of Z11-16:Ald and Z11-16:Ac in a binary blend or six-component blend, the 1 mg dose of these two compounds was the optimum dose for male attraction in both taxa. This pheromone identification is the second of any New Zealand Noctuidae species and suggests similarities with some Australian native Noctuidae species. In addition, this study reports the first occurrence of Z3Z6Z9-23:Hy in the sex pheromone blend of any Noctuidae species.