Diversion of Oviposition by Atherigona soccata (Diptera: Muscidae) to Nonhost Maize with Sorghum Seedling Extract

Abstract

The oviposition responses of Atherigona soccata Rondani, commonly known as the sorghum shootfly to seedlings of maize, which is not a host plant, that had been sprayed with acetone extracts of sorghum seedlings were investigated. Sorghum cultivars susceptible to the shootfly(CSH-1), resistant (IS 2122, IS 2123, and IS 2205), and wild sorghum, Sorghum arundinaceum (Desv.), were used. The possibility also was investigated of diverting shootfly egg laying in the field to maize sprayed with sorghum seedling extract. All of these extracts elicited significantly greater oviposition (67–91%) on treated maize seedlings than (9–33%) on untreated controls. Oviposition stimulant activity of CSH-1 extract decreased as the extracted plants grew older. The results suggest that a chemical oviposition stimulant is perhaps widespread among cultivated and wild sorghums, and it may serve as a kairomone in host finding and egg laying by the shootfly. In the field, maize seedlings sprayed with sorghum seedling extract served as good a host as the susceptible sorghum (‘Serena’) for shootfly oviposition. About 50–66% of shootfly eggs were laid on maize sprayed with sorghum seedling extract, either planted around sorghum or in strips alternating with strips of sorghum, compared with 6–17% laid on untreated maize. Because shootfly larvae cannot survive on maize, diverting oviposition onto maize would result in a reduction of the pest population. Our studies demonstrated the potential for using an oviposition stimulant for diverting shootfly eggs onto nonhost plants as a strategy for the management of the pest.