Differential effects of plant species on a mite pest (Tetranychus urticae)and its predator (Phytoseiulus persimilis): implications for biological control

The influence of plant species on the population dynamics of the spider mit e pest, Tetranychus urticae, and its predator, Phytoseiulus persimilis, was examined as a prerequisite to effective biological control on ornamental n ursery stock. Experiments have been done to investigate how the development , fecundity and movement of T. urticae, and the movement of P. persimilis w ere affected by plant species. A novel experimental method, which incorpora tes plant structure, was used to investigate the functional response of P. persimilis. Development times for T. urticae were consistent with published data and did not differ with plant species in a biologically meaningful wa y. Plant species was shown to have a major influence on fecundity (P < 0.00 1) and movement of the pest mite (P < 0.01), but no influence on the moveme nt of the predator. The movement of both pest and predator was shown to be related to the density of the adult pest mites on the plant (P < 0.001). Pl ant structure affected the functional response, particularly in relation to the ability of the predator to locate prey at low densities. The impact of these findings on the effective use of biological control on ornamental nu rsery stock is discussed.