Improving the scope and delivery of weather-based decision models for plant diseases in wheat

Project Code : PRR06-370

Project Lead

Ron Pitblado - Weather Innovations Incorporated

Objective

To develop and implement an improved early warning system for Fusarium head blight and other wheat foliar diseases

Summary of Results

Head and foliar diseases such as Fusarium head blight (FHB) (Fusarium spp.), powdery mildew (Erysiphe graminis) and Septoria leaf blotch (Septoria tritici) can significantly decrease yield and quality of wheat, especially when weather conditions are favourable for disease development. Fusarium head blight may also render wheat grain unfit for humans and livestock consumption due to contamination with mycotoxins released by the disease causing organisms. Sprays with foliar fungicides are among most readily available control options for growers to protect wheat crops from these diseases. However, because most of these products are protective and disease incidence, thereby damage levels may change from year to year, growers need reliable tools to make sound management decisions on whether or when it is economically warranted to spray.

As result of this project, an upgraded and improved DONcast system and a new WHEATcast model were developed to assist wheat growers in determining the risk and the appropriate timing for applying foliar fungicides to better manage these diseases.

DONcast is a weather-based advisory system used to predict risk of FHB disease and potential deoxynivalenol (DON) toxin levels (in ppm) in wheat grains at harvest. The original DONcast model was designed to use current and forecast local weather data and historic climate normals along with a number of agronomic factors (such as level of disease resistance of the wheat variety, tillage and crop rotation practices). However, the agronomic factors could not be adequately incorporated into the method chosen to deliver DONcast. This made it inefficient to deliver accurate DON predictions and useful fungicide application recommendations. In addition, the previous, multiple advisory regional maps used as the main output of the original DONcast model were inaccurate and confusing to growers. These led to a low adoption of the system.

The upgraded DONcast uses additional leaf wetness data (measured with a cylindrical leaf wetness sensor) and agronomic information (including wheat variety, tillage practices and crop rotation history) in calculating predictive DON values. As such, the modified DONcast is capable of providing field-specific recommendations, thus it is now called site-specific DONcast (ssDONcast). These modifications have improved the predictive accuracy of ssDONcast by over 80%. With the ssDONcast, a single daily chart is delivered to provide a probability of high, medium or low risk of DON levels at harvest along with a recommendation on which of the fields would benefit from fungicide applications in terms of greatest potential return on investment. The current ssDONcast calculator is adapted for the Ontario wheat growing region.

Available since spring 2008, the ssDONcast calculator is delivered and accessible through the Weather Innovations Incorporated (WIN) website. During the 2008 season, 670 growers signed up for this service registering 1,715 wheat fields in Ontario. In 2009, WIN will continue to deliver the new ssDONcast to wheat producers across Ontario, expanding the service area to include Quebec producers located along the Ontario-Quebec border.

WHEATcast is a new spray advisory model developed to provide fungicide application guidance for the control of powdery mildew and Septoria leaf blotch in wheat. The model uses cumulative disease severity values calculated based on leaf wetness and hourly temperatures during the wet periods. A two level risk warning is delivered with this model to indicate an initial Caution suggesting growers inspect their fields for a final decision and an Alert suggesting control action to be taken before the Alert threshold is reached. A regional map will be developed to provide the industry with a general view of the disease status for a particular year. Commercial implementation of WHEATcast will begin in spring 2009.

Both these tools can assist producers, extension specialists, crop advisors, and other users in making, or help others make informed management decisions. By providing better management guidance, these tools have the potential to reduce the use and improve the efficacy of fungicides, thereby reducing the costs and the risks from pesticides in wheat production.

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