Quo vadis Bt cotton: a dead-end trap crop in the post Bt era in China

Given a decreasing area of Bt cotton in the Huanghe and Yangtze River valleys of China, the strategy of wide area management of cotton bollworm (Helicoverpa armigera) across Bt cotton crops needs to be revisited. We argue that the role of Bt cotton as a primary production crop can be transformed to that of a companion crop that attracts moths to oviposit and kills larvae, thereby protecting nearby primary crops such as soybean and peanut. In other words, Bt cotton could serve as a "dead-end-trap crop" (DETC) when planted surrounding or alongside the non-cotton crops in different landscapes. This is particularly practical and feasible for the small-holder farming systems in China. At the same time, such unsprayed DETC could foster larger populations of cotton aphids and become a source crop for predatory and parasitic beneficial insects of aphids. This, 'killing of two birds with one stone', or multi-functionality of DETC means they could serve as a way of reducing H. armigera at a landscape level and promote biological control services for various aphid pests in target crops. Having DETC across a landscape could also mitigate the development of H. armigera resistance to Bt toxins in the transgenic crop by minimizing Bt selection pressure. Such an approach may be more acceptable to farmers by reducing control costs and losses, benefit the environment health, enhance farmers wellbeing in China, and perhaps in other parts of the world.