Winter Breeding and Spring Migration of Helicoverpa spp. in Inland Australia, 1989-1991

Abstract

Helicoverpa (Heliothis) punctigera (Wallengren) and H. armigera (Hubner) (Lepidoptera : Noctuidae) are among the most migratory of noctuid moths. Farrow & Daly, (1987) reviewed the evidence for migration in four pest species of Helicoverpa. They concluded that H . punctigera was the most migratory of the four, and H. armigera the least, but there is no doubt that the latter is also capable of long distance movement in some circumstances (Pedgley et al., 1988). The capacity for migration is a major reason for the pest status of Helicoverpa spp. throughout the world (Fitt, 1989). In south-eastern Australia, both species, but especially H. punctigera, frequently arrive in September in regions where local overwintering is rare, or where emergence does not occur until some weeks later (Fitt & Daly, 1990). At Armidale in northern NSW, local overwintering has not been recorded, and experimentally buried pupae suffer high mortality, emerging only in late October. Nevertheless, peak pheromone trap catches are obtained in mid-to late-September (Gregg & Coombs, unpublished data). These spring arrivals are clearly immigrants, and inland regions have recently been implicated as their source (Gregg et al., 1989; 1990; Fitt et al., 1990; 1991). The progeny of spring immigrants can cause damage to winter legumes, such as field peas and beans in southeastern Australia (Smith, 1990). In Western Australia lupins are particularly vulnerable (Walden, 1990). In irrigated areas of northern NSW and Queensland, spring immigrants can be the source of damaging outbreaks on cotton in November and December if there are sufficient cultivated or wild hosts to support the intervening generation (Fitt et al., 1990; 1991). To understand the origins of these spring outbreaks, we have operated a network of pheromone and light traps, and conducted surveys for winter breeding, over much of inland Australia for the last three years. In this paper we summarise findings related to areas of winter breeding and possible migration patterns.