Can we bust moths, not pupae?

Abstract

The title of this article is deliberately provocative. Pupae busting has been an icon of resistance management for the cotton industry, since the first Insecticide Resistance Management Scheme (IRMS) for pyrethroid insecticides in 1984. Combined with windows for application of specific chemical groups, it has formed the basis of these schemes ever since. It provides an effective means of killing overwintering pupae which have been exposed to selection pressure towards the end of the season. Pupae busting has been carried forward into RMPs for Bt cotton, beginning with Ingard in 1996, and then Bollgard II. Many in the industry might consider it almost sacrilegious to suggest removing it. Yet many growers dislike pupae busting. It costs money - Cotton CRC economists have estimated a cost of $26 per hectare in fuel, labour and depreciation. More significantly, it interferes with farming systems. It is incompatible with minimum tillage, which is widely adopted in dryland farming systems and brings many benefits in reducing soil erosion, conserving soil moisture and improving carbon sequestration. These issues are most pressing for dryland cotton growers, since irrigated growers often have to perform operations in normal ground preparation which serve the purpose of pupae busting, especially for back-to-back cotton crops. Yet even for irrigated growers, the need to pupae bust can often restrict rotation crop options, and prolonged wet weather can expose growers to the risk of being non-compliant with RMPs, triggering impositions such as additional refuge planting in the next season.