IPM in the transgenic era: a review of the challenges from emerging pests in Australian cotton systems

Abstract

Abstract. The Cotton Catchment Communities Cooperative Research Centre began during a period of rapid uptake of Bollgard II ® cotton, which contains genes to express two Bt proteins that control the primary pests of cotton in Australia, Helicoverpa armigera and H. punctigera. The dramatic uptake of this technology presumably resulted in strong selection pressure for resistance in Helicoverpa spp. against the Bt proteins. The discovery of higher than expected levels of resistance in both species against one of the proteins in Bollgard II ® cotton (Cry2Ab) led to significant re-evaluation of the resistance management plan developed for this technology, which was a core area of research for the Cotton CRC. The uptake of Bollgard II ® cotton also led to a substantial decline in pesticide applications against Helicoverpa spp. (from 10-14 to 0-3 applications per season). The low spray environment allowed some pests not controlled by the Bt proteins to emerge as more significant pests, especially sucking species such as Creontiades dilutus and Nezara viridula. A range of other minor pests have also sporadically arisen as problems. Lack of knowledge and experience with these pests created uncertainty and encouraged insecticide use, which threatened to undermine the gains made with Bollgard II ® cotton. Here we chronicle the achievements of the Cotton CRC in providing the industry with new knowledge and management strategies for these pests.

Australian Cotton Germplasm Resources

“…The strong reliance on insecticides continued on the remaining 70% of conventional cotton and led to ongoing selection for resistance to insecticides in H. armigera, secondary pest problems and selection of pesticide resistance in these secondary pests. For instance, by the early 2000's spider mites were resistant to organophosphates, the pyrethroid bifenthrin and chlorfenapyr, and cotton aphids were resistant to organophosphates, the carbamate pirimicarb and pyrethroids [12].…”

“…Reduced spraying for Helicoverpa has allowed survival of pale cotton stainers (Dysdercus sidae), jassids (Austroasca viridigrisea) and thrips (Frankliniella schultzei and F. occidentalis) late in the season and in some years these species have all caused damage and sporadically required control [12].…”

“…It also led to a massive decline in pesticide use (by about 85% [13]), especially relative to earlier years but also in comparison with contemporary conventional cotton that had also significantly reduced its reliance on pesticides. This technology essentially saved the cotton industry from insecticide World Cotton Germplasm Resourcesresistance in H. armigera, although a pre-emptive Bt resistance management strategy was initiated [12].…”

The interaction between diet breadth, geography and gene flow in herbivorous insects

“…Nezara viridula is an occasional pest of many crops in eastern Australia where it has highly variable seasonal and local abundance (Clarke 1992;Wilson et al 2013). In recent years N. viridula has become a more significant pest of cotton (Gossypium hirsutum) in eastern Australia because of a reduction in the use of the broad-spectrum pesticides, that previously suppressed their numbers, following the widespread planting of transgenic Bt cotton (Trapero et al 2016;Wilson et al 2013).…”

“…In recent years N. viridula has become a more significant pest of cotton (Gossypium hirsutum) in eastern Australia because of a reduction in the use of the broad-spectrum pesticides, that previously suppressed their numbers, following the widespread planting of transgenic Bt cotton (Trapero et al 2016;Wilson et al 2013). Predicting when and why N. viridula reaches numbers that require control is difficult because this insect is an extreme generalist that feeds on host plants from over 30 families (Todd 1989) and the spatiotemporal availability of host plants is not consistent (Rew et al 2005;Tillman et al 2009;Walker et al 2005).…”