Fees or refuges: which is better for the sustainable management of insect resistance to transgenicBtcorn?

Abstract

The evolution of resistance in insect pests will imperil the efficiency of transgenic insect-resistant crops. The currently advised strategy to delay resistance evolution is to plant non-toxic crops (refuges) in close proximity to plants engineered to express the toxic protein of the bacterium Bacillus thuringiensis (Bt). We seek answers to the question of how to induce growers to plant non-toxic crops. A first strategy, applied in the United States, is to require Bt growers to plant non-Bt refuges and control their compliance with requirements. We suggest that an alternative strategy is to make Bt seed more expensive by instituting a user fee, and we compare both strategies by integrating economic processes into a spatially explicit, population genetics model. Our results indicate that although both strategies may allow the sustainable management of the common pool of Bt-susceptibility alleles in pest populations, for the European corn borer (Ostrinia nubilalis) one of the most serious pests in the US corn belt, the fee strategy is less efficient than refuge requirements.

Regulation of a Spatial Externality: Refuges versus Tax for Managing Pest Resistance

“…Whether the non-Bt area serves as a natural refuge for the Bt area and contains the evolution of resistance depends on pest dispersal between the two patches and on the heterogeneity between farmers. The simulations in Vacher et al (2006) suggest that the fee strategy alone would not work for Bt corn in the US Corn Belt, but could dominate the refuge strategy for a smaller and more heterogeneous ecosystem.…”

“…The present paper tackles the same issue as Vacher et al (2006), using a different methodology. We design a two-period spatially explicit model of crop production with pest resistance in which farmers make crop variety choices.…”

“…Instead of relying on simulations of calibrated dynamic models which lack generality and transparency in the mechanisms at play, we use a stylized representation of the problem from which we are able to derive analytical solutions. We analyze the impact of two key parameters pointed out in Vacher et al (2006): pest mobility and farm heterogeneity. Depending on the levels of these parameters, we assess whether a refuge or a tax or subsidy on Bt seeds can restore efficiency and, if not, how each of these instruments performs in managing the evolution of pest resistance.…”

“…In contrast, in our paper each farmer takes into account how his own actions affect resistance development. In Vacher et al (2006) as in our paper, farmers are sorted geographically and face heterogeneous pest attacks. The fee strategy alone, in the absence of mandatory refuges, leads to a spatial segregation of Bt and conventional corn.…”

Strategies for building trust with farmers: the case of Bt maize in South Africa

“…Refuge areas, or refugia, are the buffer zones of non-Bt maize (susceptible to stalk borers) planted in close proximity to Bt maize to provide a pool of stalk borers susceptible to Bt maize. This is meant to delay development of resistance to the toxic protein produced by Bt [18]. As South Africa was the first African country to report stem borer resistance to the Bt toxin, the need to ensure a proper refuge area is becoming more important.…”