Immersion treatments for imported chrysanthemum cuttings to controlwestern flower thrips, Frankliniella occidentalis (Pergande) in greenhouses

Abstract: In Ontario, preliminary assessments suggest that substantial numbers of westernflower thrips (WFT) [Frankliniella occidentalis (Pergande)] are introduced on importedchrysanthemum cuttings. Because of the difficulty in detecting thrips at this stage of productionand controlling them as needed, an alternative approach is to treat all cuttings before they enterthe greenhouse. This study evaluates the strategy of immersing cuttings prior to propagationusing various treatments considered as reduced risk.Hot water, insecticidal soap and horticultural oil immersion treatments were assessed forphytotoxicity and their efficacy in controlling WFT. The efficacy of the entomopathogenicmicrobials Beauveria bassiana and Steinernema feltiae also was examined. Spinosad wasevaluated as a comparison.Hot water treatments provided 67-98% mortality of WFT life stages; horticultural oil 67-100% mortality; B. bassiana 93-95% mortality; and S. feltiae 53-63% mortality. Spinosadprovided 27-58% control of larvae and adults.