Yield, development, and quality response of dual‐toxin Bt cotton to Helicoverpa spp. infestations in Australia

Abstract

To verify current thresholds for Bollgard II® cotton in Australia, the impact of Helicoverpa spp. (Lepidoptera: Noctuidae) larvae on yield, development, and quality under various infestation intensities and durations, and stages of growth, was tested using small plot field experiments over two seasons. Infestation with up to 80 eggs m−1 of Helicoverpa armigera (Hübner) and Helicoverpa punctigera Wallengren showed that species, infestation level, and stage of growth had no significant effect on yields of seed‐cotton or lint and on maturity and fibre quality. The duration of infestation of white flowers with H. punctigera neonates (maximum of every day for up to 4 weeks) had no impact on the yield of seed‐cotton or lint, maturity, and fibre quality, but when 100% of flowers were infested (compared with 0 or 50%), seed‐cotton and lint yields were significantly reduced and maturity was delayed. Infestation with up to 18 medium H. armigera larvae m−1 at several plant stages did not significantly affect yields of seed‐cotton and lint, maturity, and fibre quality. A heliocide spray applied on a commercial farm at the current threshold resulted in a significantly higher lint yield, compared with a farm where no spray was applied. In conclusion, Bollgard II® cotton is highly resistant to Helicoverpa spp. infestation.

Bisexual Attract-and-Kill: A Novel Component of Resistance Management for Transgenic Cotton in Australia

“…This has the advantage of directly reducing the numbers of larvae which would otherwise be subjected to selection pressure and require pupae busting. While this could be done using insecticides targeting the larvae ( Lu et al 2012 ), Magnet has the advantage of being a more cost-effective option (with product being applied to 1 row in 72 as opposed to a broadcast over-the-top larvicidal insecticide application). It is also more efficient with regard to application costs and time and minimizes impact on natural enemies of Helicoverpa spp.…”

Enhancing Integrated Pest Management in GM Cotton Systems Using Host Plant Resistance

“…Genetic modification (GM) of cotton containing genes to express protein(s) from the bacteria Bacillus thuringiensis ( Bt ), which are highly effective at killing the larvae of some lepidopterans ( Naranjo, 2011 ; Wilson et al, 2013 ), was introduced in the mid-1990s and greatly reduced pesticide use. Bt -cotton is highly efficacious against target pests ( Lu et al, 2012 ), at the same time having a negligible effect on non-target insects ( Whitehouse et al, 2005 , 2014 ; Tian et al, 2015 ) and causing little or no harm to most other organisms, including people ( Mendelsohn et al, 2003 ; Herman et al, 2009 ). Globally, 25 million hectares were planted in 2013 to Bt -cotton, representing 68% of all cotton grown in the world.…”

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

“…Instead, normal foraging behaviour combined with seasonal variations in the phenotypic expression of proteins allows some susceptible larvae to survive (Lu 2011). Experiments with real and simulated pest damage, based on densities and distributions of surviving larvae seen in the field, showed that current thresholds are valid, and probably perhaps slightly conservative in terms of the impact of damage on yield (Lu et al 2012a(Lu et al , 2012b). …”

“…infestation (Lu et al 2012a). Nevertheless, these crops are regularly checked for the presence of surviving larvae, and in some fields Helicoverpa spp.…”