A comparison of repetitive releases of single or multiple natural enemy species on the suppression of Bemisia tabaci infesting poinsettias

Abstract

The repetitive release of Eretmocerus eremicus (Mercet) (Hymenoptera: Aphelinidae) to manage Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a promising strategy on poinsettias in protected culture. Management of B. tabaci, however, may be improved if releases include multiple natural enemy species that attack different B. tabaci life stages. In this study, we investigate whether suppression of B. tabaci on poinsettias is improved by the combination of E. eremicus and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) compared to either natural enemy alone at release rates 1.2 – 2.7-fold the cost of conventional insecticide inputs. We found that all natural enemy treatments provided significant suppression when starting whitefly populations were below 13.7 ± 1.7 immatures per plant. The combination of E. eremicus and A. swirskii performed equally well compared to either natural enemy alone, in both a substitutive and additive design. These effects, however, were density dependent; neither natural enemy alone nor the combination of natural enemies suppressed whiteflies if initial whitefly density was above 40.8 ± 2.5 immature whiteflies per plant.