Potential parasitoids for management of fall armyworm (Spodoptera frugiperda J. E. Smith [Lepidoptera: Noctuidae]) in horticulture systems of tropical Australia

Abstract

The fall armyworm, Spodoptera frugiperda, is a highly polyphagous pest, native to the tropical and subtropical regions of the Americas that invaded the Australian mainland in 2020. Since its incursion into Australia, management has largely relied on the use of different synthetic insecticides. Given pesticide resistance genes and reduced sensitivities to a variety of pesticides are already present in the population, there is a need to investigate alternative management approaches that can be incorporated into an IPM programme such as biological control. A fundamental step in establishing the potential of biological control is identifying the potential natural enemies that may be deployed in pest management. In this study, we undertook a series of surveys to identify potential parasitoids for fall armyworm and assessed parasitism rates in Western Australia (WA) and the Northern Territory (NT). Approximately, 1900 larvae of fall armyworm were sourced from maize, sweet corn, okra and sorghum fields, reared and observed for the emergence of parasitoids. Ten species of larval parasitoids from five families were recorded during the surveys with Cotesia ruficrus (Haliday) (56.14%) and Exorista xanthaspis (Wiedemann) (50%) being the most abundant larval species in WA and NT, respectively. Other parasitoids found include four recently described species, Euplectrus frugiperdata Fagan-Jeffries, Chelonus trojanus Fagan-Jeffries, Coccygidium necatrix Atkin-Zaldivar & Fagan-Jeffries, Coccygidium mellosiheroine Atkin-Zaldivar & Fagan-Jeffries, and previously named species, Megaselia scalaris (Loew) and some unidentified Tachinidae. Two species of egg parasitoids, Trichogramma pretiosum (Riley) and Telenomus remus (Nixon), were recovered with field parasitism rates of 7.81% and 10.16%, respectively. Overall, the occurrence of potential egg and larval parasitoids in Australian horticulture systems provides a unique platform to develop a conservation or augmentative biological control approach to manage fall armyworm in Australia.