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Screening of biopesticides and risk-reduced products for the management of powdery mildew in cut gerbera

Project Code: BPR14-070

Project Lead

Janice Elmhirst Elmhirst Diagnostics and Research, British Columbia, Canada


To screen reduced risk disease management products for the management of powdery mildew in cut gerbera

Summary of Results


Powdery mildew, caused by Erysiphe sp. or Podosphaera sp. is one of the most important diseases in ornamental crops in Canada. The disease in cut gerbera was identified as a priority issue by growers at the 2013 Canadian Biopesticides Priority Setting Workshop, and the Pest Management Centre’s Pesticide Risk Reduction was tasked to identify a promising reduced-risk product for the management of this disease.

A screening trial was carried out in 2014 to assess a number of reduced risk disease management products which were thought to have potential as efficacious solutions to this problem.


Five products (treatments) were evaluated in the screening trial for their efficacy for the management of powdery mildew and for tolerance of the crop in greenhouse-grown cut-flower gerbera compared to the commercial standard, 2% Rhapsody ASO. Four applications were made for each treatment at a weekly interval. Disease was assessed weekly until harvest. Disease severity (percent leaf area covered with mildew) and diseased incidence of leaves were assessed for the efficacy measurement.


Of the five products evaluated, three products, Cyclone combined with surfactant Liberate, PureSpray Green Spray Oil 13E, and Influence LC, showed significant efficacy for the suppression of powdery mildew. Cyclone reduced diseased leaves by up to 50% and disease severity by 46-71% during the course of the screening trial and the effective suppression was maintained until harvest, while Influence and PureSpray Green Spray Oil 13E showed significant reduction in disease severity by 36-45%, their effectiveness generally declining after the fourth application. None of the products resulted in phytotoxicity to the cut gerbera plants tested in this trial.

Based on results derived from the screening trial, Cyclone was recommended for further testing in 2015 to generate value data to support a possible User Requested Minor Use Label Expansion (URMULE) request for registration for this use.

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