Effect of Neoseiulus californicus-spider mite ratio for controlling Tetranychus urticae in a chrysanthemum greenhouse

Abstract

The effect of a predatory mite, Neoseiulus californicus (McGregor) release to control a population of two-spotted spider mite, Tetranychus urticae Koch, was investigated in a chrysanthemum greenhouse. After spider mite inoculation, we released N. californicus females at prey:predatory ratios of 20:1, 10:1, or 5:1. The population densities of spider mites began to decrease 4 weeks after predator release and reached almost 0 after 5 weeks. We found that N. californicus could reduce the population density of spider mites, when the N. californicus/T. urticae ratio was 10:1 or more.