Screening of biopesticides and risk-reduced products for the management of downy mildew on hop

Project Code: BPR12-040

Project Lead

Gary Coukell  Integrated Crop Management Service (ICMS), British Columbia, Canada

Objective

To screen promising products for the management of downy mildew in hop by evaluating efficacy of seven risk-reduced products

Summary of Results

Background

The growth of hops is on the rise in Canada, with most of the crop currently being produced in British Columbia, Ontario and Quebec. Downy mildew, caused by Pseudoperonospora humuli, is one of the most important diseases in hops in Canada and occurs wherever hops are grown. In Canada, metalaxyl-m and copper are registered for use against downy mildew in conventional hop production; however concern about pathogen resistance to the two products is increasing. At present, organic producers have essentially no product to use for the management of this disease. Downy mildew in hop was selected as a priority issue by growers at the 2011 Biopesticides Priority Setting Workshop. This project was undertaken to seek promising reduced-risk products through a screening trial for management options for this disease.

Approaches

Seven products, identified through a review of research literature and in consultation with stakeholders, were included in the screening project. In 2011 these products were screened for their performance in a field trial with six applications at a weekly interval. Three products, Regalia, Actinovate SP, and Organocide, appeared to be promising and were selected for evaluation again in field efficacy trials in 2012. In the 2012 efficacy trial, 2 application rates applied four times at weekly intervals were assessed for each of the three products. Diseased leaf incidence and severity were assessed at weekly intervals until harvest in both the screening and efficacy trials. Marketable yields from each plot were assessed and expressed in kilograms per hectare (kg/ha). Crop tolerance (phytotoxicity) was assessed at the same time as disease incidence and severity assessments, using a 0-100 percent (%) visual rating scale.

Results

In the 2011 screening trial, after six applications were completed, all products showed significant suppression to disease severity at day 63 after the first application, but the disease severity was reduced only by approximately 20% by each of products and incidence by 30-50%. In the 2012 trial, the three products, Regalia Maxx SC, Actinovate SP, and Organocide, all showed significant reduction in disease incidence and severity six days after first application at both tested rates. In general, the three products maintained significant suppression of hop downy mildew until harvest, with disease severity or incidence reduced by up to 50%, compared to the untreated. In general, all treatments of three products provided comparable efficacy with the commercial standard Revus for the suppression of the disease. No crop phytotoxicity was observed in any of the treatments with these three products in screening and efficacy trials, suggesting that the products may be useful additions to the pest management toolbox for suppression of downy mildew in hops.

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