Fusarium Head Blight in Spring Wheat - Project

Wheat growers in most parts of Ontario are very familiar with the damage that Fusarium Head Blight, also known as "scab", can cause in quality, yield and economics. The infection of fusarium head blight is very dependent on the weather conditions from 3 to 7 days prior to heading and 3 to 10 days after the wheat heads have emerged. Determining when to apply Folicur fungicide is often difficult. 2002 was the 2^nd year of the Fusarium Head Blight in Spring Wheat Project.

Forecast Model

The predicted risk information was presented as colour-coded maps. These maps forecast the amount of toxin (DON in ppm) that would accumulate if the wheat was at Zadok's Stage 59 (75% of the heads in a canopy completely emerged from the flag leaf) on the date of a map. The Fusarium Risk Prediction Model information was updated 3 times per week (Monday, Wednesday & Friday afternoons) from June 15^th to July 15^th. The colour-coded fusarium prediction maps were available to growers and crop scouts on the Weather INnovations Inc.at the Ridgetown College Fusarium Information website.

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2002 Project Results

In the 2^nd year of this project, there were 30 side-by-side on-farm comparisons strips/reps of a "No Folicur" check strip compared to a strip where Folicur was sprayed at approximately 2 to 3 days following the Day 0 (75% Heads Emerged) stage. Accessing each field to get the timing of application at Day 2 to Day 3, was a challenge with the sudden increased daytime temperatures, which shorten the time that the wheat plant was at the "75% Head Emerged to Flowering" stage.

Only a few fields reached 75% Head Emergence during the last week of June, which was about 1 week later than last year. During the last week of June, there were seasonal temperatures with variable rainfall and the fusarium model was predicting 1 to 2 ppm DON levels. It is interesting to note that the highest DON level sample was from a field heading the last week of June. Also note that the spring wheat variety, 5700 PR, is known to be more susceptible genetically to fusarium infection.

Most of the growers involved in this project sprayed the Folicur during the 1^st week of July. During this period, the weather turned hot and dry, with daytime temperatures over 32 ° C. These conditions are known to reduce the survival of the fusarium spores. The model prediction maps turned green, indicating low DOM levels. In most of these fields, there was low to no actual fusarium infection or DON toxin levels.

Note that the fields that did have DON levels greater than 0.5 ppm in the Check strips had a DON level reduction of 30% from the use of Folicur. The average yield advantage to the use of Folicur fungicide from the 30 comparisons was less than 1 bushel per acre this year. The lack of yield response can be attributed to the generally lower leaf disease pressure, particularly powdery mildew, than what was experienced in 2001.

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Conclusions

Similar to 2001, the weather conditions of 2002 were not conducive to heavy fusarium pressure and therefore did not warrant the use of Folicur. The maps generated by the Fusarium Prediction Model reflected the risk of DON toxin levels when used immediately prior to spraying. This project has validated that under field scale situations of higher DON levels (>0.5 ppm), Folicur reduced the DON toxin levels by approximately 30%. Overall, the project has further improved the understanding of how to manage fusarium head blight in spring wheat with the use of Folicur fungicide, the use of the Fusarium Prediction Model, and other factors, such as variety selection and crop rotation. The 3^rd and final year of the project will be in the 2003 season.

Related Links

• Fusarium Risk Maps for Western Ontario, Weather INnovations Inc.

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