Biological control of aphids in the presence of thrips and their enemies

Gerben J Messelink,Arne Janssen,Maurice W Sabelis,Chantal M J Bloemhard

doi:10.1007/s10526-012-9462-2

Abstract

Generalist predators are often used in biological control programs, although they can be detrimental for pest control through interference with other natural enemies. Here, we assess the effects of generalist natural enemies on the control of two major pest species in sweet pepper: the green peach aphid Myzus persicae (Sulzer) and the western flower thrips Frankliniella occidentalis (Pergande). In greenhouses, two commonly used specialist natural enemies of aphids, the parasitoid Aphidius colemani Viereck and the predatory midge Aphidoletes aphidimyza (Rondani), were released together with either Neoseiulus cucumeris Oudemans, a predator of thrips and a hyperpredator of A. aphidimyza, or Orius majusculus (Reuter), a predator of thrips and aphids and intraguild predator of both specialist natural enemies. The combined use of O. majusculus, predatory midges and parasitoids clearly enhanced the suppression of aphids and consequently decreased the number of honeydew-contaminated fruits. Although intraguild predation by O. majusculus on predatory midges and parasitoids will have affected control of aphids negatively, this was apparently offset by the consumption of aphids by O. majusculus. In contrast, the hyperpredator N. cucumeris does not prey upon aphids, but seemed to release aphids from control by consuming eggs of the midge. Both N. cucumeris and O. majusculus did not affect rates of aphid parasitism by A. colemani. Thrips were also controlled effectively by O. majusculus. A laboratory experiment showed that adult predatory bugs feed on thrips as well as aphids and have no clear preference. Thus, the presence of thrips probably promoted the establishment of the predatory bugs and thereby the control of aphids. Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions. Future work on biological control should focus on the impact of species interactions in communities of herbivorous arthropods and their enemies.

Highlights

Generalist predators are increasingly used to control multiple pests in biological control programs (Chang and Kareiva 1999; Symondson et al 2002; Sabelis et al 2008; Messelink et al 2010)
Generalist predators are often used in biological control programs, they can be detrimental for pest control through interference with other natural enemies
Our study shows that intraguild predation, which is potentially negative for biological control, may be more than compensated by positive effects of generalist predators, such as the control of multiple pests, and the establishment of natural enemies prior to pest invasions

Summary

Introduction

Generalist predators are increasingly used to control multiple pests in biological control programs (Chang and Kareiva 1999; Symondson et al 2002; Sabelis et al 2008; Messelink et al 2010). An important reason for this success is the ability of these predators to colonize crops when pests are absent or present at low densities because they can feed on alternative food sources. This can result in high predator densities relative to those of the invading prey, thereby preventing a pest outbreak. Another reason is that generalist predators can be very effective in suppressing multiple species of plant pests. Several studies have shown that predatormediated interactions between pest species (apparent competition; Holt 1977) can enhance pest control within a time scale relevant to pest control programs (e.g., Karban et al 1994; Hanna et al 1997; Harmon and Andow 2004; Messelink et al 2008, 2010)

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