Efficacy of Pheromone-based Mass Trapping in Management of Fall Armyworm Spodoptera Frugiperda (Lepidoptera: Noctuidae) in Maize Farms

Abstract

Fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) has rapidly spread in Kenya and has emerged as a major pest of maize (Zea mays L). To manage fall armyworm (FAW) infestations in maize, many small scale farmers have relied heavily on use of synthetic chemical insecticides that has been associated with environmental pollution, food crop contamination, development of insecticide resistances in the pests and high costs. Various organizations, including international research organizations based in Kenya, have advised farmers on cost-effective integrated pest management (IPM) strategies, but some of the advice is not applicable to the farming practices and systems of smallholder farmers. The use of semiochemical-based pest management practices as part of IPM strategies suitable for smallholder farmers, on the other hand, has not been evaluated. This study addressed this knowledge gap by determining the efficacy of pheromone-based mass trapping as a means of reducing FAW infestation levels in maize plant. The study was conducted at Kenyan Agricultural and Livestock Research Organisation (KALRO) Katumani Research Centre in Machakos County, the maize seeds (Variety - KDV-1) were planted on 4th April 2021 and harvested on 13th August 2021. Data from 13th April (after emergence) to 13th August 2021 was used in the analysis in this study. The experiment utilized a randomized block design with four treatments, four replications and a control plot, with each experimental plot measuring 25 x 50 meters (0.125 hectares). The four treatments and four replications of the experimental blocks involved randomly placing female sex pheromone traps at four different densities of 8, 16, 24, and 32 traps/ha. The extent of FAW infestation and the number of captured FAW adult male moths per trap, per plot and maize phenological stages were tabulated twice a week. In this study, the prevalence of fall armyworm infestation was higher than the recommended action threshold level in all the treated experimental plots At the early whorl stage, against a recommended action threshold of 20%, the infestation rates ranged from 58.45% to 79.1%, while at the late whorl stage, the infestation levels ranged from 53.6% to 73.6% against a recommended action threshold of 40%, and finally, at the reproductive stage, the infestation rates ranged from 65.5% to 75.0% against a recommend action threshold of 20%. FAW infestation varied significantly across maize phenological stages (F7, 284 = 28.33, p < 0.001) and trap densities (F4, 284 = 52.39, p < 0.001), with the phenological stages and trap densities interacting significantly (F28, 284 = 1.83, p = 0.008). There was no point of intersection between moth catches and FAW infestation levels per trap density, indicating that the two parameters did not have an inverse relationship in this experiment. In conclusion, mass trapping with synthetic sex pheromones was ineffective in suppressing FAW populations or reducing FAW infestation damage on maize plants, and thus should not be used as a "stand alone" control method but can be developed as part of an IPM package for FAW management.