Enhanced efficacy of pheromone-treated entomopathogenic nematodes against whiteflies in foliar applications with a gel adjuvant

Abstract

The whitefly, Bemisia tabaci, has a diverse host range that includes many economically important crops. Plant damage and crop loss resulting from infestations of this insect pest averages >$140 million (USD) annually in the southeast U.S. and requires different management approaches. Entomopathogenic nematodes are biological control agents targeting insect pests. The entomopathogenic nematode Steinernema feltiae is particularly virulent against B. tabaci and several other insect pests with aboveground life stages. However, unpredictable efficacy limits the use of entomopathogenic nematodes in aboveground/ foliar pest management strategies. Ascaroside pheromone extracts have been shown to significantly improve the efficacy of entomopathogenic nematodes under field conditions that challenge their survival and efficacy. The objective of this study was to evaluate the influence of ascaroside pheromones on Steinernema feltiae in foliar applications against B. tabaci. Cotton plants were selected as hosts for whiteflies, and 5 ml solutions of nematodes (with and without other treatments) were used for foliar applications. Evaluations occurring through laboratory and cage trials were sampled across seven days. Exposure to the pheromone treatment resulted in higher S. feltiae efficacy as marked by higher B. tabaci adult mortality up to 79.98 % and reduced B. tabaci nymph survival down to 5.92 %. In earlier aboveground trials using entomopathogenic nematodes, Barricade® (a gel) facilitated higher efficacy by reducing the risk of desiccation. Barricade® was included in foliar applications for comparison and the gel improved entomopathogenic nematodes’ efficacy in foliar applications. This study highlights a new avenue for the foliar application of entomopathogenic nematodes with enhanced efficacy.