Fall armyworm in West Africa: Earwig predation potential and insecticide selectivity

Description of the subject. The fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) is a major pest of staple cereal crops established in West Africa since 2016. Recently, earwigs have been observed consuming S. frugiperda immature stages in maize fields. Objectives. In this study, we evaluated the potential of earwigs, Diaperasticus erythrocephalus (Olivier) (Dermaptera: Forficulidae) to consume fall armyworm eggs and larvae in a laboratory setting. In addition, we compared the selectivity of the ten most used bio- and insecticides on this predatory species as well as on its prey for identifying products compatible with an integrated pest management strategy. Method. Predation was assessed by feeding earwigs ad libitum and susceptibility tests following the adapted IRAC 020 protocol. Results. Our results suggest that earwigs play an important role in the regulation of the fall armyworm: one individual consumes a mean of 90.3 ± 16.5 eggs or 36.4 ± 8.7 larvae per day. We found emamectin benzoate and spinetoram to be effective for controlling the fall armyworm, while not affecting the survival of this predator. On the other hand, chlorpyrifos-ethyl, methomyl and spinosad are not only effective against this pest but also highly toxic to the predator. Conclusions. We discuss the potential of these results in the development of an integrated pest management program against this invasive pest. In particular, we recommend training the farmers on natural enemy recognition and their conservation practices.