Evaluation of Organocide for the management of powdery mildew in greenhouse cucumber

Project Code: BPR12-060

Project Lead

Janice Elmhirst   Elmhirst Diagnostics and Research

Robert Doell     Ag-Quest, Incorporated

Gary Coukell    Integrated Crop Management Service (ICMS)

Objective

To develop efficacy and crop tolerance data in support of a regulatory submission for Organocide (sesame oil) for the management of powdery mildew in greenhouse cucumber

Summary of Results

Background

In Canada, approximately 0.2 million tonnes of greenhouse cucumbers are produced annually with a value of $ 254 million. Powdery mildew is a serious disease that occurs widely threatening the production of greenhouse cucumber across Canada. The fungi infect cucumber leaves producing white powdery spores on the upper leaf surface. The pathogens absorb nutrients from the leaf cells and diseased leaves eventually dry up and die. Crop yield is reduced during severe infestations due to leaf senescence. Adding a reduced risk solution to the control toolbox will help growers improve management of this disease while minimizing the risk for the pathogens to develop resistance to currently used fungicides. The biopesticide Organocide was selected as a potential solution by growers at the 2011 Biopesticides Priority Setting Workshop for the management of powdery mildew in greenhouse cucumber. This product would be suitable for use in both conventional and organic production systems.

Approaches

In 2012 three greenhouse trials were conducted on cucumbers in Minto, Manitoba, Abbotsford, British Columbia and Langley, British Columbia. Greenhouses had either a history of powdery mildew or cucumber plants were inoculated by introducing powdery mildew infected cucumber leaves. Organocide treatments were applied as foliar sprays at rates of 16 millilitres per litre (ml/L) and 20 ml/L 2 to 6 times at 7-day intervals. The solution volumes per plot were 500 litres per hectare (L/ha), 900 L/ha or 1500 L/ha, varying with plant size. The untreated check was sprayed with water alone. In the trials, Organocide was compared with the commercial standard Nova 40W (myclobutanil) both alone and in combination with Kocide 2000 (copper hydroxide).

Disease incidence, disease severity and crop tolerance were assessed prior to the first application and then weekly after each application.

Disease incidence was determined as percentage of leaves per plant with at least one powdery mildew lesion. Disease severity was determined as percentage of leaf area per plant covered with powdery mildew, estimated on a scale of 0 to 5 where 0 equals no disease, 1 equals 1-10%, 2 equals 11-25%, 3 equals 26-50%, 4 equals 51-75%, and 5 equals 76-100% leaf area covered. Area under the disease progress curve (AUDPC) was calculated on the mean disease severity over the course of the trial.

Crop tolerance to Organocide was assessed by visually rating symptoms of phytotoxicity on a scale of 0-100%.

Results

Results indicate that Organocide provided adequate control of powdery mildew. When applied at 16 and 20 ml/L under moderate to high disease pressure, Organocide provided up to 62.5% reduction in disease severity and up to 94.6% reduction in disease incidence. No significant difference was observed on efficacy between the two rates of Organocide.

Organocide combined with Kocide 2000 performed better than Organocide or Kocide applied alone. Generally, the level of control with Organocide was less than that provided by the commercial standard, Nova 40W. The cucumber plants appeared to have excellent tolerance to Organocide as no phytotoxicity symptoms were observed.

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