Abstract

Exotic and native predatory mites play an important role in biological control of mite and insect pests in Iran. Intraguild predation (IGP), the killing and consumption of potential food competitors, is a decisive mechanism co-determining if an exotic predator become dominant over native species or not. Direction and strength of IGP, however, could be affected by high temperatures. Therefore, we evaluated the temperature-dependent predation rates and prey preference of adult females of exotic Amblyseius swirskii (Athias-Henriot) and native Typhlodromus bagdasarjani Wainstein & Arutunjan females in the presence of the spider mite Tetranychus urticae Koch and/ or intraguild (IG) larvae. Experiments were conducted at two alternating high temperature regimes (40°C /15°C) and (35°C/13°C), 16:8 (L: D) h photoperiod and 65±5 % RH. For both species, gravid females were individually placed in closed cages and provided with IG prey (larvae) with or without spider mites (eggs and larvae). Consumption rates on IG prey and spider mites were recorded every 24 h over 5 consecutive days. Without spider mites, exotic and native females consumed similar numbers of IG prey at 35°C/13°C, but the IG predation rates of native, but not exotic predator females, decreased under heat stress. Irrespective of temperature, native predator females clearly preferred spider mites over IG prey, whereas the IG-, but not spider mite predation rates, decreased under heat stress. Contrary, the exotic predator females consumed similar numbers of spider mites and IG prey at 35°C/13°C, but more IG prey under heat stress. Our results indicate that (1) independent of temperature, exotic A. swirskii females are high-risk IG predators for native T. bagdasarjani, and (2) heat stress altered the IG interactions between the exotic and native predator females in opposite directions. Native T. bagdasarjani IG prey larvae were more endangered to become victim of the exotic predator A. swirskii under heat stress, whereas risk to be killed by the native predator was lower for the exotic IG prey under heat stress. Thus, the native T. bagdasarjani should respond to the presence of exotic predator A. swirskii with effective IG anti-predator behavior, to ensure coexistence between the two biocontrol agents in crops.