Efficacy of pheromone-based mass trapping in the management of fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize farms

Abstract Introduction: The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), has emerged as a major pest of maize in Kenya. To control FAW infestations in maize, smallholder farmers have relied on the use of chemical pesticides, which are associated with environmental pollution, food crop contamination, insecticide resistance and high costs. However, the efficacy of pheromone-based mass trapping for mitigating FAW infestations has not been assessed in smallholder farming. Methods: The experiment utilized a randomized block design with four treatments, four replications and a control plot, with each experimental plot measuring 25 × 50 m (0.125 hectares [ha]). The four treatments and four replications of the experimental blocks involved randomly placing sex pheromone traps at four different densities of 8, 16, 24, and 32 traps/ha. The FAW infestation and the number of captured FAW adult male moths per trap, per plot and maize phenological stage were tabulated twice a week. Results: At the early whorl stage, the FAW infestations ranged from 58.5% to 79.1%; at the late whorl stage, the infestation rates ranged from 53.6% to 73.6%; and at the reproductive stage, the infestation rates ranged from 65.5% to 75.0%. FAW infestation varied across maize phenological stages ( F 6, 289 = 33.16, p < 0.001) and trap densities ( F 4, 284 = 52.39, p < 0.001), with the phenological stages and trap densities interacting ( F 24, 289 = 2.14, p = 0.002).Conclusions: The FAW infestation rates were higher than the recommended action threshold level in all the treated experimental plots. Additionally, the number of captured FAW adult male moths did not have an inverse relationship with infestation level at any of the trap densities. Mass trapping with synthetic sex pheromones was ineffective at suppressing FAW populations or reducing FAW infestation damage in maize plants. Although landscape diversity and preceding crops may have confounded the results. However, this approach may not be useful as a “standalone” control method, and it can be developed as part of an integrated pest management package for FAW monitoring.