Biological control of Echinothrips americanus by phytoseiid predatory mites and the effect of pollen as supplemental food

The poinsettia thrips, Echinothrips americanus Morgan, is an upcoming pest in greenhouse crops, causing serious damage in various vegetable and ornamental crops through extensive foliage feeding. We assessed which stages of E. americanus are attacked and killed by the phytoseiid predatory mites Amblyseius swirskii (Athias-Henriot), Amblydromalus limonicus (Garman and McGregor), Euseius gallicus Kreiter and Tixier and Euseius ovalis (Evans). Both the predation and oviposition rates were assessed in the laboratory to evaluate which mite species is potentially the most effective predator of E. americanus. In two greenhouse trials with non-flowering sweet pepper plants, we compared the efficacy of the predators E. gallicus and E. ovalis with A. swirskii and we assessed how this was affected by the application of cattail pollen. All stages of E. americanus, except adults, were consumed by all species of predatory mites. The highest predation and oviposition rates were recorded for A. limonicus followed by A. swirskii and E. ovalis when first and second larval stages were provided as prey, but E. ovalis appeared to be the best predator of thrips pupae. Euseius gallicus displayed very low predation and oviposition rates compared to the other species of predatory mites. Cattail pollen did not support the population growth of poinsettia thrips, but it strongly increased the predatory mite population densities, particularly those of E. ovalis. Both A. swirskii and E. ovalis significantly reduced thrips densities on plants. The application of pollen significantly enhanced the control of E. americanus by A. swirskii; this was not the case for E. ovalis. Euseius gallicus did not reduce densities of E. americanus on sweet pepper plants, not even at high densities in the presence of pollen.