Host Strain Analysis Revealed Corn-pecific Strain of Spodoptera frugiperda (Lepidoptera: Noctuidae) on Maize in Three Agro-ecological Zones of Nigeria

Abstract

The fall armyworm, Spodoptera frugiperda is an invasive and trans-boundary lepidopteran insect pest. This moth species is native to the Americas but has been reported on the African continent in recent times, where its polyphagous larva has caused much damage to field maize. The fall armyworm occurs in two highly destructive strains – the ‘corn’ and ‘rice’ strains. Though morphologically identical, the two strains have different host preferences and varying susceptibility to conventional insecticides. Management of fall armyworm on maize and other crops will be enhanced by the molecular identification of existing strain or strains in local populations of the pest in existing African agro-ecologies. However, information on the presence of both strains is scarce and unclear for the different agro-ecological zones of Nigeria. Using a Polymerase Chain Reaction – Restriction Fragment Length Polymorphism (PCR-RFLP) method, strain identification analysis of larvae from 22 maize farms spread across the humid forest, derived savannah and southern guinea savannah agro-ecological zones of Nigeria was carried out. Results showed that all the larvae screened belong to the corn strain implying that only the corn strain is present on maize in the agro-ecological zones. Knowledge of the type of fall armyworm strain in African agro-ecologies is useful for the selection of appropriate bio-control agents and chemical pesticides against the pest on the continent.