Helicoverpa punctigera (Wallengren) and H. armigera (Hubner) have a number of characteristics which make them highly successful pests of numerous crops in Australia, including cotton (Fitt 1989). They are highly mobile, have a broad host range and can increase in numbers rapidly when conditions are favourable. Current pest management relies on regular sampling and application of pesticides when thresholds are exceeded. It seems unlikely that the need for regular crop checking can ever be abandoned, but here we discuss prospects for predicting changes in Helicoverpa abundance which may assist pest managers in the future