At best, manufacturers hope their RMPs might sustain Bt efficacy for up to 10 years. The loss of Bt will thereafter be essentially permanent, and will trigger all sorts of difficulties in the decades ahead in managing a wide range of lepidopteran insects. The high doses of Bt endotoxin expressed in the transgenic crop will assure that no target pest larvae would survive on a transgenic crop, and hence no resistant individuals could emerge. Refugia are effective. Thus resistant individuals would not emerge.
Resistance is a rare, recessive trait that carries significant genetic fitness costs.
Bt endotoxins is independent. Since there are dozens of Bt endotoxins, this assumption is used to argue that even if resistance occurred to one endotoxin, a company could just switch to another endotoxin to which the insect would be susceptible until it could evolve resistance to the new endotoxin. By switching endotoxins, the company could dramatically delay, and perhaps prevent, the loss of Bt as a useful pesticide. New evidence published in the last year, detailed below, fundamentally and irrevocably undermines these four assumptions. Furthermore, there is a consensus among most independent entomologists and experts in Bt resistance management that resistance is just a matter of time.