Integrated pest management of onion thrips (Thrips tabaci), an emerging pest of greenhouse floriculture crops in Ontario

Abstract

Integrated pest management (IPM) of thrips in greenhouses has focused primarily on western flower thrips (Frankliniella occidentalis, WFT). However, recent studies demonstrate that onion thrips (Thrips tabaci, OT) are prevalent in Niagara floriculture greenhouses. Biocontrol-based IPM programs effective for WFT appear less effective for OT, leading to outbreaks. Through studies in commercial greenhouses, laboratory assays, and greenhouse trials, this thesis examines the relative occurrence, monitoring, and management of OT in potted chrysanthemums. Data from 2019 identified outdoor populations as the likely infestation source of OT, with pressure peaking in July. Yellow monitoring cards were preferred over blue by OT but did not accurately reflect species composition in the crop at all sites. In laboratory assays, OT and WFT were equally susceptible to predatory mites, nematodes, and Beauveria bassiana. Greenhouse trials produced conflicting results suggesting that thrips behaviour on host plants may contribute to poor OT control. Management recommendations are discussed.