Host age-mediated effects on fitness traits of five Anastatus parasitoids: Implications for optimizing biological control of Riptortus pedestris.

Abstract

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a widely distributed polyphagous pest, associated with soybean stay-green syndrome, causing substantial yield losses across Asia. Continued reliance on chemical control remains problematic, highlighting the need for sustainable biological alternatives. In this study, we comparatively evaluated the parasitism performance, host-feeding behavior, developmental traits, and host-age preference of five egg parasitoids of the genus Anastatus (A. dexingensis, A. fulloi, A. gansuensis, A. japonicus, and A. shichengensis) on R. pedestris eggs of different ages (0-, 2-, 4-, and 6-d-old). All five parasitoid species successfully completed development on R. pedestris eggs, with offspring emergence rates ranging from 82% to 100%. Parasitism and host-feeding were strongly influenced by host egg age, with all species showing a clear preference for 0- to 2-d-old. Anastatus dexingensis and A. japonicus parasitized the highest number of host eggs (13.5 and 12.3 eggs/24 h, respectively), whereas the thelytokous A. gansuensis exhibited the strongest host-feeding activity (3.8 eggs/24 h). In contrast, A. fulloi and A. shichengensis produced no female progeny, whereas A. dexingensis and A. japonicus produced less than 20% female offspring. Developmental duration generally increased with host age, indicating that older host eggs may be less suitable for parasitoid development. Overall, A. dexingensis and A. japonicus appear well suited for short-term suppression of R. pedestris through inundative releases, whereas the thelytokous A. gansuensis shows strong potential for long-term, sustainable population regulation, making it promising for augmentative biocontrol. These findings provide a scientific basis for selecting effective Anastatus spp. and optimizing egg-stage biocontrol strategies against R. pedestris.