First report of the predatory potential and functional response of the red flower assassin bug Rhynocoris segmentarius (Germar), a natural enemy of Spodoptera frugiperda (J.E. Smith)

Abstract

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is currently the most devastating invasive arthropod pest of maize in sub-Saharan Africa. Following its first report in Ghana in 2016, control has been reliant mainly on synthetic chemicals. However, biocontrol has been an effective, sustainable, cheaper, and environmentally friendly option for FAW management. We tested the potential of the red flower assassin bug, Rhynocoris segmentarius (Germar) (Hemiptera: Reduviidae) as a natural enemy candidate for augmentative biocontrol of FAW in Ghana by assessing its predatory rate and functional response under laboratory conditions in Ghana. The feeding responses of the five nymphal instars and adults (female and male) of R. segmentarius were tested against three larvae ages of FAW: (i) < 1 day old or newly emerged (NE), (ii) 2 days old, and (iii) 6 days old, at six different prey densities: 5, 15, 25, 30, 35, and 40, respectively. All life-stages of R. segmentarius successfully attacked, killed, and fed on the larvae of S. frugiperda, and exhibited a Type II functional response. However, the first and second nymphal stages of R. segmentarius did not successfully attack or kill six-day-old FAW larvae. Females had a significantly higher attack rate (7.79 ± 1.01) and the shortest handling time (1.17 x 10–1) than all life-stages. Our results suggest that R. segmentarius is a potential candidate for augmentative biocontrol of S. frugiperda.