Pollen subsidies promote whitefly control through the numerical response of predatory mites

Several studies have shown that biological control of pests can be improved by supplying extra food to natural enemies. This increases population levels of the enemies, resulting in decreases in pest densities. In theory, however, supplying food can also have negative effects on biological control. We specifically tested for such negative effects, using a predator-prey system consisting of the whitefly Bemisia tabaci (Gennadius) and a predatory mite Amblyseius swirskii (Athias-Henriot). This predator attacks eggs and young instars of the whitefly, but also feeds on pollen. We added pollen to populations of predators and whiteflies on isolated cucumber plants. Although the set-up of our experiments would favour the occurrence of a negative effect of the addition of pollen on biological control, we found increased control throughout the experiment. This shows that the control of whiteflies by A. swirskii can be improved by supplementing the predators with pollen.