Combining refuges with transgenic insect releases for the management of an insect pest with non-recessive resistance to Bt crops in agricultural landscapes

Abstract

Reinforcing the high-dose/refuge strategy with releases of transgenic insects has been posited as a method for simultaneously managing agricultural pest populations and resistance to transgenic crops. Theoretical and empirical studies have shown that these approaches can work when deployed against closed populations and the assumptions of the HDR strategy are met. However, field-evolved resistance is often linked to non-recessive resistance or refuge non-compliance, and pest management regimes are likely to take place at the landscape-level. It is therefore important to understand how effective such strategies are when resistance is non-recessive, and how they could be employed in agricultural landscapes. We developed a spatially-explicit model to investigate the efficacy of strategies combining refuges with transgenic insect releases to manage a pest with non-recessive resistance in agricultural landscapes. We compared two release strategies, area-wide releases and localised releases targeted at population hotspots, and analysed the effects of refuge and release parameters on population and resistance dynamics. Area-wide releases reliably achieved landscape-level pest eradication. Localised releases also eradicated the pest when low release thresholds were combined with high release ratios, and maintained the pest at low densities when insufficient to achieve extinction. Reinforcing refuges with localised releases also greatly enhanced the probability of resistance extinction. However, when resistance remained in the population, localised releases prevented resistance from reaching fixation rather than greatly delaying or reversing resistance evolution. Our work indicates that combining refuges with simple release policies is effective for landscapelevel pest suppression when the HDR assumptions are violated, but more nuanced release strategies may be required to enhance the benefits to resistance management.

Managing resistance evolution to transgenicBtmaize in corn borers in Spain

“…If approved for cultivation, this Bt maize could be grown in rotation with maize MON 810 enabling the alternation of Bt proteins with a different mode of action, thus avoiding repeated selection pressure encountered in continuous maize MON 810 cultivation, as is often practiced in Spain [71]. Additional approaches, such as combining the HDR strategy with mass releases of sterile insects [124] or male GE insects with a female-specific self-limiting gene [125,126] have been proposed or applied for simultaneously managing agricultural insect pest populations and resistance to Bt crops. In the southwestern United States and northern Mexico, for instance, the combined use of Bt cotton and mass release of sterile pink bollworm (Pectinophora gossypiella) moths has enabled the successful suppression of this invasive pest [124] and the replacement of refuges with mass releases of sterile insects.…”

The Spatiotemporal Dynamics of Insect Predator–Prey System Incorporating Refuge Effect

“…According to the Cardano formula, the above one-dimensional cubic Equation (13) can be equated to (m…”

“…The dynamics of insect populations are not only influenced by various abiotic factors, such as temperature [ 5 , 6 ], altitude [ 7 ], and humidity [ 8 ], but also largely mediated by predator–prey interactions [ 9 , 10 ]. Refuge effects, a vital influence factor in the insect predator–prey systems [ 11 , 12 , 13 ], provides a degree of protection for insect populations from predation [ 11 , 14 , 15 ]. Such spatiotemporally discrete systems are complex, sensitive and prone to chaos [ 16 , 17 , 18 , 19 ], whose fluctuations in species abundance or growth rate tend to occur simultaneously across spatial sites [ 20 , 21 ], leading to elusive spatial and temporal dynamics [ 22 , 23 ].…”

RNAi silencing CHS1 gene shortens the mortality time of Plutella xylostella feeding Bt‐transgenic Brassica napus

“…5,6 Previous studies found that target insects such as Helicoverpa armigera, Helicoverpa zea, and P. xylostella have evolved resistance to Bt-transgenic crops. [6][7][8][9] 9 Plutella xylostella has exhibited high-level resistance to Bt biotoxins sprayed in the field. 10 Hence, it is urgent to develop strategies that can delay the resistance of target insect to Bt-transgenic plants.…”

“…Previous studies found that target insects such as Helicoverpa armigera , Helicoverpa zea , and P . xylostella have evolved resistance to Bt‐transgenic crops 6–9 . Plutella xylostella has exhibited high‐level resistance to Bt biotoxins sprayed in the field 10 .…”