Refuge strategies for managing resistance to Bt maize in fall armyworm in smallholder farming systems: a case study from China

Abstract

The invasion of fall armyworm Spodoptera frugiperda poses a significant threat to the maize production of smallholder farmers in Asia and Africa. Bt maize is an effective measure for controlling this pest, but resistance management strategies tailored to the smallholder farming systems in the old world remain poorly understood. Surveys conducted from 2021 to 2022 in key infestation regions of Yunnan and Guangxi, China, revealed that an average administrative village includes 633 households, each cultivating 0.22 ha of maize per season, with 95.68% of fields smaller than 0.33 ha. Laboratory and field studies indicated that the high dispersal ability of fall armyworm larvae facilitated frequent larval movement between Bt and non-Bt maize within seed mixtures and structured refuges in smallholder farming systems. Resistance evolution models showed that establishing structured refuges covering 10–20% of households at the village level significantly slowed resistance development. This study proposes a village-based structured refuge strategy, proportionally allocated according to household distribution. The strategy is simple and feasible for smallholder farming systems in developing countries, offering a novel approach for managing resistance to Bt maize in fall armyworms.