Host plant volatiles released by Bracharaira brizantha and Desmodium spp. and their effects on the behaviour of fall armyworm

Abstract

Desmodium spp. and Napier-like grasses are widely used as push-pull systems for mange fall armyworm (FAW) in Africa. However, the responsible cues for the olfactory responses of the FAW was not been identified yet. Hence, this study was conducted to identify volatile compounds release by Desmodium spp. and Bachiraria brizantha plants and determine their role on behaviour modification of FAW adults and the larvae. Four different plant species i.e., B. brizantha, Desmodium heterophullum, D. triflorum and D. interim were collected, and volatiles were extracted using dynamic head space and solvent extraction methods. The chemical compounds were identified using GC-MS. Behavioural studies were conducted for selected volatiles based on availability. This study identified 29 volatile compounds released by Desmodium spp. where 30 compounds were identified from B. brizantha. Behaviour study results indicated that females were attracted to nhexane (72.73%) and Limonene (-) (66.67%), where naphthalene (70%) showed a repellent behavior. Males were significantly repelled by 3- Hexen-1-ol, Limonene (-), and Limonene (+). Neonates significantly attract to Limonene (-) (69.23%) and repel by 1-Octen-3-ol. Therefore, it can be concluded that this behavior modified volatile compounds can be used to develop semiochemical based green pest management strategies.