Development of an attracticide for heliothine moths: from laboratory bioassay of plants to commercial field trials

Abstract

Our research group, in collaboration with a small Australian-based company, has developed an attracticide (Magnet®) for 'Helicoverpa' moths, that has been recently registered for cotton, beans and sweet corn in Australia. We first screened a number of host as well as non-host plants of 'Helicoverpa' spp. in the laboratory using a two-choice olfactometer to identify plant volatiles attractive to the moths. The majority of the plants tested were significantly attractive to male and female moths, with the Australian natives, 'Angophora floribunda' and several 'Eucalyptus' species being the most attractive plants. Volatile profiles of these plants were determined by GC-MS. Synthetic equivalents of plant volatiles were then tested in the olfactometer singly or in combination as blends. Volatile blends consisting of floral and green leaf compounds were more attractive to moths compared with individual volatiles. For a polyphagous species like 'Helicoverpa armigera', we proposed an approach of "super blending" of volatiles that were in common between attractive plants, rather than mimicking the blend of plant odours emitted by a particular attractive plant. Field wind tunnels and traps were used to test candidate blends in the field. Small-scale field trials on various crops were conducted to determine the efficacy of a five-component blend combined with a small amount of toxicant. Field trials were also conducted to determine its effects on non-target organisms. Commercial trials in cotton demonstrated substantial reductions in heliothine numbers not only in the Magnet®-treated field but also in nearby untreated fields.