Management of the spider-mite population in a vinylhouse vinery by releasing Phytoseiulus persimilis Athias-Henriot onto the ground cover

Abstract

It has been observed that Phytoseiulus persimilis, a predatory phytoseiid mite, is unlikely to settle on tall host plants, such as woody plants. In 1995, an experiment was performed in a vinylhouse vinery (1,000 m2) in an attempt to manage the spider-mite population of Tetranychus kanzawai on grape leaves throughout the growing season, by releasing P. persimilis onto the grass ground cover in the spring. Two releases of P. persimilis (a total of 8,000♀♀) late in May and early in June drove the spider-mite population on the ground cover almost to extinction early in July. Throughout July, the spider-mite density was held at 10% of that in the control vinery where no predators had been released. Early in August, spider mites reoccurred in the vinery, because P. persimilis had died out due to lack of prey. However, since the population density of spider mites was very low (<1.73♀♀/leaf), no chemical control was required throughout the growing season. A survey in the following March confirmed that no P. persimilis had survived the winter in or around the vinery.