Functional response of two Neoseiulus species preying on Tetranychus urticae Koch

Abstract

Neoseiulus californicus and N. cucumeris are both potential candidates for the biological control of key pests in China. Whereas N. californicus has mainly been used to control spider mites, N. cucumeris has been released for the control of thrips and spider mites. To understand the potential of the combined use of N. californicus and N. cucumeris to suppress outbreaks of Tetranychus urticae, the predatory performance of these Neoseiulus species against different stages of T. urticae, either separately or in combination, was evaluated by assessing their functional responses in the laboratory. The values of the attack rate coefficient (α) of N. californicus to each stage of T. urticae exceeded those of N. cucumeris, whereas the handling time (Th) of N. californicus was longer than that of N. cucumeris, except when attacking the larvae of T. urticae. Especially at the higher prey densities, N. cucumeris consumed more eggs per day than N. californicus, whereas N. californicus consumed more larvae. Both predators killed similar numbers of nymphs at each density when tested singly. The searching efficiency of the Neoseiulus species decreased with increasing prey densities, and for all stages of T. urticae, the searching efficiency of the Neoseiulus species tested singly was lower than when they were tested together. The study indicates the potential of mixed releases of N. californicus and N. cucumeris for the management of spider mite infestations.