Abstract

Phytoseiid predatory mites exert an important influence on mite and insect pests in biological control. Intraguild predation (IGP) is a common phenomenon among predators including arthropods which share the same extraguild prey. The non-native predatory mite Amblyseius swirskii is used as a biological control agent against thrips, whiteflies and spider mites in different greenhouses in Iran. While Typhlodromus bagdasarjani, the native prospective predatory mite, acts in the area as well. Interaction between the two mentioned predators is not well known and they may co-occur in ecosystems and act as food competitors, interrupting biological control success of each other. We examined intraguild predation and oviposition behavior of the female predators in the presence of the other species at an alternating high temperature regime (40°C /15°C), 16:8 (L: D) h photoperiod and 65 ± 5 % RH. Adult females of each predatory species were individually placed into Petri dish arenas and were provided with adequate larvae of IG prey over 5 consecutive days. Predation rates and selected sites for oviposition were recorded every 24 h. Each treatment was replicated 20-25 times. Both T. bagdasarjani and A. swirskii females attacked the larvae of each other in the mentioned condition. The daily IG predation rates of T. bagdasarjani females were 0.18 A. swirskii larvae. However each A. swirskii female killed 0.37 T. bagdasarjani larvae daily. Both the figures are far less than the females IG predation performance in normal constant 25°C temperature condition (1.39 and 9.5 IG larvae/female/day for T. bagdasarjani and A. swirskii females, respectively; our previous study). In addition, oviposition behaviour of both predatory species was affected by the presence of heterospecific eggs. Nearly 25 percent of both species preferred not to lay egg in patches either with or without heterospecific eggs. Most T. bagdasarjani females (13 out of 15) laid eggs in patches without A. swirskii eggs, while 10 out of 14 A. swirskii females do preferred patches with T. bagdasarjani eggs over patches without heterospecific eggs. Therefore the observed intraguild predation along with oviposition site selection behavior of the predators in the mentioned temperature did not reduce the intense of IGP between two species which in turn may demote coexistence of the two predator species. However, further semi-field and field experiments are needed to draw a better conclusion of IGP between the two species by detail.