For a long time, pest control In the cotton industry has depended on a narrow range of broad-spectrum insecticides. However, because of increasing insecticide resistance, the future Is uncertain and alternatives are urgently required. There is a need to conserve natural control in the crop, principally parasites and predators, and exploit other biological control agents where possible. Unfortunately, most of these are vulnerable to chemicals and attempts to integrate them with chemical control are likely to be only partially successful. However, microbial insecticides In the form of microbialchemical mixtures can have a role in delaying the development of resistance.

During the 1988/89 cotton season trials were conducted to evaluate the potential of synthetic pheromones to control the pink -spotted boll worm, Pectinophora scutigera, by mating disruption

Last year I spent several months at Rothamsted Experimental Station in the U.K., as a Churchill Fellow, studying biochemical toxicology in H. armigera was inspired by the Insecticide Resistance Groups very practical application of basic research on biochemical resistance mechanisms, to develop sensitive and reliable methods for monitoring resistance in field populations. If felt that in H. armigera too, that we will be able to use the power of biochemical and molecular genetic techniques, not only to gain a fundamental understanding of the processes, but to exploit this knowledge to study problems in the field. In this paper, I want to share some of these very exciting developments with you.

A complex of pests attacks the Australian cotton crop, none more important than the cotton bollworm, Heliothis armigera. and insecticides are considered necessary for its control. H. armigera has a long history of insecticide resistance in Australia. To DDT in the early 1970's and more recently, in 1983. to the synthetic pyrethroids. Since 1983 , H. armigera insecticide resistance has been the subject of an insecticide resistance management program in NSW and Queensland. A knowledge of resistance mechanisms is fundamental to the resistance management strategy, so management can be targeted at avoiding or counteracting the mechanisms.

The Australian Field Crops Resistance Management Strategy has been in place now for 7 seasons. The impact of the Strategy on resistance levels is monitored in three areas; the Namoi and Gwydir river valleys of nonhem NSW (a temperate cotton monoculture), the Emerald Irrigation Area of central Queensland (a sub tropical mixed cropping area) and a sample of the unsprayed Refugia centred on Inverell in northern NSW. Resistance to both pyrethroids and endosulfan is assessed, as these two groups account for over 80% of the insecticides used against Heliothis spp. in Australian cotton. Studies with the oxidase inhibiting synergist piperonyl butoxide (Pbo) have indicated that the dominant mechanism of pyrethroid resistance in the field is via oxidative detoxification. This has led to the investigation of two possible chemical countermeasures for managing pyrethroid resistance: synergists and structurally modified pyrethroids (also called resistance breaking pyrethroids). A brief summary of each of these findings will be given followed by an outline of the future for managing pyrethroid resistance.

Small parasitic wasps, scientifically known as Trichogramma, are used as biological control agents of moth pests in overseas countries, thereby reducing the need to use insecticides. These wasps attack the egg stages of moths, killing them before they hatch and cause damage. Large numbers of Trichogramma need to be produced and released per hectare of crop (hundreds of thousands) to have an affect on a pest population.

The Bureau of Rural Resources has estimated the area in central Queensland potentially suitable for raingrown cotton production at 60-80,000 ha. With cotton prices above 1989$ 400 per bale, raingrown production can be highly profitable with even mediocre management. While the needs, risks, and management options for raingrown cotton have been dissected by other speakers at this conference, what happens to an insect management strategy which is totally dependent on the remedial use of insecticides should this potential suddenly be realized? Clearly it is important that we develop, now, a management strategy that reduces our reliance on conventional chemical control of insects and which is stabilised by the integration of some alternative pest control methods.

The purpose of our four-year study on the Darling Downs was 1) to investigate the population dynamics of heliothis and to quantify the significance of the major controlling influences (parasites, predators, pathogens, weather and host plant effects) on population change; and 2) to assess the potential for an management approach to the suppression of populations through the practical manipulation controlling

Heliothis spp. are very successful as pests for a number of reasons (Fitt 1989): adult moths are highly mobile and have a high reproductive rate, larvae can utilize a wide range of host plants including most crops, and successive generations can develop resistance to pesticides. Management of such pests in commercial crops relies on regular scouting to provide information on egg and larval densities within each crop, and their likely resistance levels. We believe that the local management of Heliothis could be improved if predictions of the densities and the origin of Heliothis eggs on each crop could be made several days in advance. Regional management strategies (see Murray. these proceedings) and insecticide resistance management (see Forrester, these proceedings) would also benefit if overall seasonal predictions of likely densities for each species of Heliothis could be made with confidence. Such information would be available if we understood the population dynamics of Heliothis on a regional scale. To this end we are developing. a series of simulation models under the name "HEAPS" (HEliothis Annigera and Punctigera Simulation) (Hamilton and Fitt 1988).