A Molecular Marker to Identify Spodoptera frugiperda (JE Smith) DNA in Predators' Gut Content

Spodoptera frugiperda is a serious pest of maize and other crops worldwide. The integration of control tactics is recommended for S. frugiperda suppression because reports of insecticide and Btplant-resistance are frequent. Biological control agents would be an alternative to improve S. frugiperda control in agricultural areas. We constructed a species-specific molecular marker to detect S. frugiperda DNA in predators' gut content and estimated the predation rates of ladybugs and earwigs on S. frugiperda in maize crops. Predators were sampled in Pirassununga, São Paulo state, Brazil, in 2020 and 2021. Using the species-specific molecular marker in laboratory conditions, we estimated the half-life time to detect S. frugiperda DNA in the gut contents of Hippodamia convergens as 6.16 h and Doru luteipes as 25.72 h. The weekly predation rate of S. frugiperda by predators in maize crop varied from 0 to 42.1% by ladybugs and from 0 to 9.2% by D. luteipes. Predation events on S. frugiperda by predators were more frequent during the maize reproductive stage. Our results confirmed that predators might contribute to S. frugiperda suppression in maize fields. However, further studies of prey-predator interactions and agricultural landscapes are essential for a better understanding of predator dynamics in crops.