Final answer:
The refuge strategy advocated by Tabashnik for delaying the development of resistance to Bt toxins in pests involves providing non-Bt crop areas—or refuges—where susceptible insects can survive without selective pressure from Bt, allowing them to dilute the population of resistant pests.
Step-by-step explanation:
The "refuge" strategy proposed by Tabashnik to slow the evolution of Bt resistance relies on "crop rotation". This approach involves organizing the planting of non-Bt crops alongside Bt crops, thereby providing areas where pests can survive without being exposed to Bt toxins. By doing so, susceptible insects survive in these refuges, which helps to dilute the presence of resistant genes in the population when they mate with potentially resistant insects from the Bt crop areas.
This strategy does not include rotating crops with different Bt toxins, continuous cultivation of Bt crops, eliminating Bt crops entirely, or increasing the concentration of Bt in crops. Instead, it emphasizes the importance of pest-resistant crops and the reduction in the reliance on environmentally toxic chemical pesticides, as well as enhancing biodiversity by integrating non-Bt crops.
Main elements of the refuge strategy include the use of pest resistant cultivars and maintaining a balance by reducing the amount of synthetic chemical pesticides used. This practice supports the ecosystem, allowing for natural pest control measures and creating a more sustainable agricultural system. Moreover, this approach is in line with strategies such as interplanting and providing environments favorable to natural enemies of crop pests. This strategy is part of integrated pest management (IPM) practices which seek to minimize pest damage in the most environmentally sensitive and economically efficient way.