Contests between beneficial natural enemies: brood‐guarding parasitoids vs. foraging predators

Abstract

Beneficial insects, such as natural enemies, are important to agro‐ecosystem functioning and thus agricultural production. Parasitoids and predators can provide sustainable long‐term solutions to pest problems (biological control), reducing the need for expensive and sometimes polluting pesticide applications. When several species of beneficial insects are present, their pest control actions may be additive, synergistic, or disruptive. One form of disruptive interaction between parasitoids and predators is direct interspecific contest for access to individual pests (the resource to be exploited). This study evaluated behavioural interactions between brood‐guarding wasps, Goniozus nephantidis (Muesebeck) (Hymenoptera: Bethylidae), which are known to engage in intra‐specific contests, and a predatory bug, Cardiastethus exiguus (Poppius) (Hemiptera: Anthocoridae), which attack the same pest species, Opisina arenosella (Walker) (Lepidoptera: Oecophoridae), a major pest in coconut production systems. Dyadic parasitoid–predator and predator–predator contests were staged to determine the factors that influence the behaviours within, and outcomes of, such interactions. Parasitoids were aggressive towards predators, sometimes killing them, but predators were not aggressive towards parasitoids. Biting and stinging only occurred when there was a host larva present. In the absence of the parasitoid that had oviposited onto a host, predators often consumed the parasitoid’s eggs. Egg consumption sometimes occurred when the parasitoid was present. Intra‐specific competition between pairs of predators was also evaluated: adults were aggressive towards each other, but interactions were not fatal. Biting was more common when there was no prey larva present. When a larva was present, predators were observed feeding simultaneously. We conclude that direct parasitoid–predator interactions are likely to influence pest population dynamics, possibly reducing the overall suppression of O. arenosella by its natural enemies.

The evolutionarily stable strategy, animal contests, parasitoids, pest control and sociality

“…Owing to their small size, their field-biology is often not readily observable and their success in biocontrol is not always easy to predict. It has been recognized that inter-and intra-specific contest behaviours, which are relatively readily observable in the laboratory, can be used as indicators of whether given combinations of natural enemies are likely to coexist in the field and provide the desired biocontrol services [39,[60][61][62][63]. Contest behaviour has also been used to consider how parasitoids may respond to the presence of invasive crop pests.…”

Ecology, invasion history and biodiversity-driven management of the coconut black-headed caterpillar Opisina arenosella in Asia

“…However, intraguild predation e.g. between G. nephantidis and C. exiguus may influence pest population dynamics and the overall efficacy of natural or augmentation biological control ( Velasco-Hernandez et al., 2021 ). In southern Vietnam, (unidentified) earwigs are commonly associated with O. arenosella , and their relative contribution to BHC biological control is currently being assessed (unpublished data).…”