Comparative efficacy of biocontrol agents for managing western flower thrips (Frankliniella occidentalis) and onion thrips (Thrips tabaci) in greenhouse ornamentals

Integrated pest management (IPM) of thrips in horticulture greenhouses have been studied primarily with the management of western flower thrips (Frankliniella occidentalis, WFT) in mind. Although WFT are still the primary thrips pest in greenhouse ornamentals, recent studies have confirmed that horticulture greenhouses are often inhabited by multi-species thrips communities. Onion thrips (Thrips tabaci, OT) is the second most common thrips species, making up approximately one third of thrips found in floriculture greenhouses in the Niagara region of Canada. While biocontrol based IPM programs have been managing WFT successfully, outbreaks of OT are occurring more frequently leading to increases in visible feeding damage and crop losses. In order to improve the success of biocontrol based thrips IPM for both thrips species, we must determine which components of this IPM program do not work as well for OT compared to WFT, and identify how to make up for those deficiencies. A series of laboratory and greenhouse experiments were conducted to compare the efficacy of commonly used thrips predators (Amblyseiulus swirskii, Neoseiulus cucumeris, A. degenerans, Amblydromalus limonicus, Orius insidiosus), entomopathogenic fungi (Beauveria bassiana), and entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora) against WFT, OT and mixed thrips populations. The results are presented and recommendations for improving the success of biocontrol based IPM programs are discussed.