Bemisia tabaci (Hemiptera: Aleyrodidae) in commercial poinsettia: impact of biocontrol on demographic trends

Abstract: Bemisia tabaci (Gennadius) is an economically important pest of food and ornamental plants world-wide and is now recognized as a cryptic-species complex. In many regions, it is a particularly important pest of greenhouse poinsettia and two cryptic species from the B. tabaci complex, Mediterranean (Biotype Q) and Middle East Minor 1 (MEAM1: Biotype B), often infest poinsettia crops simultaneously. In general, the Mediterranean species has greater resistance to insecticides than MEAM1. This difference in pesticide susceptibility has the potential to influence growers’ management decisions, including the use of biological control vs. insecticides, and the choice of insecticide active ingredient. However, little is known about the impact of these decisions on the demographic trends of mixed species infestations in commercial-scale greenhouses. To address this question, we conducted a season long survey of B. tabaci populations in commercial poinsettia crops in Ontario, Canada. Using a molecular diagnostic technique to identify Mediterranean and MEAM1 population within the B. tabaci complex, we provide evidence that under biological control-based management, MEAM1 can displace Mediterranean, whereas under insecticide-based management Mediterranean populations will persist. The demographic shift observed in commercial greenhouses conforms to predictions based on the observation of mixed laboratory colonies of these two species. The use of biological control for B. tabaci management (in particular mixed species infestations) has the potential to preserve the efficacy of late-season insecticide applications if needed, whereas serial applications of insecticides throughout the duration of the crop will shift mixed-populations towards Mediterranean, increasing the risk of control failures.