On-farm field demonstration of the impact of irrigation management, timing of fungicide sprays and cropping system on Fusarium head blight control in irrigated wheat production in Southern Alberta

Project Code PRR10-130

Project Lead

Ken Coles  Agricultural Research and Extension Council of Alberta

Objective

To identify and promote adoption of integrated approaches, including cultural practices and informed decision making for sustainable Fusarium head blight management in wheat production under irrigation

Summary of Results

Background

Fusarium head blight (FHB), caused by Fusarium species (spp.) is a major disease of wheat across Canada. Infection causes fusarium damaged kernels (FDK) affecting grain yield and grade. In addition, Fusarium graminearum, the most prevalent disease causing fungus, produces high levels of deoxynivalenol (DON), a mycotoxin that contaminates grains making them unfit for human and livestock consumption. The threat from this disease in wheat crops under irrigation, common in Southern Alberta, is on the rise because of the continuous build-up of pathogen inoculum and extended periods of high moisture in the field which promote disease.

Management of FHB has relied heavily on few available chemical fungicides since there have been no truly resistant wheat varieties available at the time this project was established. As part of the Pesticide Risk Reduction Program’s Fusarium head blight strategy, this project aimed to demonstrate alternative approaches to sustainable FHB management.

Approach

From 2010 to 2012, field scale trials were conducted in cooperation with nine wheat growers across southern Alberta. The project evaluated the impact of two irrigation regimes (regular irrigation and no irrigation during flowering) and fungicide application on FHB risk, crop development and wheat grain quality and yield. Fungicide treatments were applied to six fields each year. Disease ratings, including incidence (percent heads with visible symptoms of FHB), severity (percent spikelets infected on the head) were collected and a FHB index calculated (incidence times severity) at the late milk to early dough stage. Grain samples from each treatment were also assessed for levels of DON and grade and percentage of Fusarium damaged kernels (FDK) according to Grain Commission standards.

An annual survey of 25 commercial wheat fields (both irrigated and dryland) was completed to gain a better understanding of how FHB disease levels relate to common management practices. Information was collected on tillage practices, cultivar susceptibility, irrigation management and crop rotation and grain samples were collected for pathogen identification.

Results

Extreme weather conditions in all three years of the project greatly hindered the application of treatments and outcomes of the field scale trials. In 2010, spring seeding was delayed due to very wet conditions resulting in a late harvest and increased frost injury and a corresponding downgrading of the crop. In 2012, environmental conditions favoured leaf disease but not FHB development. The data generated, however, showed a number of interesting trends.

Overall, fungicide treatments reduced FDK in 12 of 15 test fields by up to 2.3 % (percent) in 2010, 1.2% in 2011 and 0.4% in 2012. With irrigation management, FDK was actually reduced up to 3.9% in one cooperator’s field in 2010 where irrigation was avoided during flowering. When combined, the reduced irrigation and fungicide treatment had the lowest FDK, suggesting that the combined approaches provide an additional benefit over either used alone. Analysis of grain samples showed that fungicide applications reduced F. graminearum levels by 7-12% and irrigation management reduced F. graminearum up to 2%. Deoxynivalenol was present at detectable limits (0.1 to 11 ppm (part per million) in most samples. Fungicide applications reduced DON by 0.2 to 3.3 ppm, while irrigation management showed a reduction in DON of 0.2 ppm in 1 of 7 fields.

Survey: F. graminearum was positively identified in grain samples from 25% of the surveyed fields and other Fusarium spp. were identified in 60% of the grain samples. Varieties susceptible to FHB were planted in 64% of the fields surveyed. Of the fields where F. graminearum had been identified in the grain samples, 71% had grown a host crop within the previous 2 years. Irrigation appears to be a key influence as 83% of F. graminearum infected grain samples were from irrigated fields.

Technology transfer: Numerous extension events organized as part of this project, such as crop walks, field schools and presentations served to inform growers about this disease. Social media tools including Facebook, Twitter and YouTube as well as the Farming Smarter website were used as platforms to distribute information resulting from this project. Small wheat plots planted each year of the study were used for diagnostic training purposes. Several handouts on FHB were developed and distributed at crop walks and training sessions.

This study suggests that proper timing of irrigation, integrated with selection of less susceptible wheat cultivars and timely fungicide treatments may be beneficial in minimizing the impact of FHB. As shown through the annual surveys, this study served to increase grower awareness about FHB presence in their fields and provided information on disease management options.

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