Reciprocal predation between the predatory mite Amblyseius swirskii and aphid predators used in Integrated Pest Management

In applied biocontrol and Integrated Pest Management programs, natural enemies may engage in competitive interactions such as cannibalism, hyperpredation, or intraguild predation. The outcome of these interactions shapes the natural enemy community eventually impacting pest management. Here, we assessed the predation of the phytoseiid mite Amblyseius swirskii on eggs of the aphid predators, Aphidoletes aphidimyza, and the hoverflies Eupeodes corollae and Sphaerophoria rueppellii. We also assessed the predation of the first instar larvae of these aphid predators on A. swirskii eggs, both in the presence and absence of aphids. In all experiments, egg predation was assessed at 24 and 48-hour intervals. On average, A. swirskii consumed 57% of the A. aphidimyza eggs (20 eggs offered per arena), 12% of the S. rueppellii eggs, and 4% of the E. corollae eggs (in both cases, 10 eggs offered per arena). The aphid predator larvae consumed fewer A. swirskii eggs in the presence of aphids, although this difference was statistically significant only for S. rueppellii. In the absence of aphids, S. rueppellii consumed 42% and 84% of the A. swirskii eggs (20 offered per arena), on the first and second day of observations, respectively. For A. aphidimyza these values ranged between 5.9% and 5.0%, and for E. corollae between 6.2% and 15%. The low predation levels by A. swirskii on the hoverfly eggs suggest that in the more complex and larger spatial scale of a crop environment, this interaction is unlikely to significantly affect the hoverfly population dynamics and their predation potential on aphids. Moreover, although the larvae of all aphid predators consumed A. swirskii eggs, only S. rueppelli exhibited high predation levels that warrant further research to assess potential implications for predatory mite abundance and biological control effectiveness.