Influence of semiochemicals present in the scales of Spodoptera frugiperda on chemotactic behavior of Trichogramma pretiosum

Abstract

Trichogramma species (Hymenoptera: Trichogrammatidae) are known to use the host's sex pheromone as a kairomone in foraging strategies. Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) deposit scales on eggs during oviposition, which may be a mechanical barrier or facilitate the action of parasitoids due to the presence of semiochemicals. This study identified the compounds in S. frugiperda scales and evaluated the chemotactic responses of Trichogramma pretiosum Riley to volatiles in host eggs and scales, as well as to synthetic equivalents of substances identified therein. Bioassays were performed with scales extracted from the wings and abdomen of females under three conditions: virgin, mated, or mated and oviposited. The parasitoids were tested in a two-choice olfactometer comparing scales, eggs, and synthetic compounds. The extracts were analyzed by gas chromatography and mass spectrometry (GC-MS) and 20 compounds were identified, among them two acetate components of the sex pheromone of S. frugiperda (Z9-14:OAC and Z11-16:OAC). Trichogramma pretiosum females did not differentiate between scales from wings and abdomen. They were more attracted to scales from virgin and mated S. frugiperda females, and these treatments did not trigger different chemotactic responses compared with eggs. The parasitoid was significantly attracted to Z9-14:OAC and Z11-16:OAC. We conclude that T. pretiosum use chemical clues in the scales to search for S. frugiperda eggs.

Biology of fall armyworm – an introduction

“…Interactions with other insects, such as competing herbivores and natural enemies, affect fall armyworm performance (Costa et al, 2022). In its native region, fall armyworm is a host to a large variety of parasitoid wasps and flies (von Mérey et al, 2012; Barreto‐Barriga et al, 2021; Traine et al, 2021), some of which are commercially available (Vargas et al, 2021). The species is also frequently attacked by predators, fungi, viruses, and entomopathogenic nemathodes (Molina‐Ochoa et al, 2003; Fallet et al, 2022).…”