Functional response of Neoseiulus californicus preying on Tetranychus urticae is affected by prey quality and host-plant acclimation

The functional response of predatory mites is affected by several biotic factors such as host plant and prey quality, which are often difficult to disentangle. For this reason, the effects of prey quality and predator acclimation to host plant-prey systems on the functional response of predatory mites are little known. The effects of prey quality were tested by offering eggs of Tetranychus urticae Koch (Acari: Tetranychidae), reared on cotton, maize, pinto bean, and tomato plants, to Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), reared on leaves of jack-bean plants. The effect of acclimation to prey-host plant systems on the functional response was assessed in N. californicus reared for successive generations in one of four T. urticae-host plant systems (cotton, maize, pinto bean, and tomato). Females of N. californicus were then offered eggs of T. urticae reared on jack-bean leaves as prey. Cotton plants drastically interfered with prey quality, assessed as the thermochemical caloric content of T. urticae eggs, resulting in a type III functional response. Females of N. californicus acclimated to the prey-cotton system also showed a type III functional response, while females in all remaining treatments showed a type II functional response. Prey quality also interfered with the attack rate of predators with a type II functional response. These results indicated that changes in the functional response after acclimation occur as an effect of nutrition. The functional response is an important characteristic of predator-prey interactions, and these results may contribute to the rearing and use of predatory mites in applied biological control. (AU)