Will Fusarium Be A Problem In The 2009 Spring Wheat Crop?

That's a several $ million question! What weather is in store for June? Fusarium infection in wheat is very much dependant on the weather that occurs around the time that the wheat heads and begins to pollinate.

Critical Infection Period

For fusarium infection to occur in the wheat head, the weather conditions 7 days prior to the wheat heading and for 5 to 10 days after the wheat heads have emerged are critical. Temperatures between 10° and 30° C and wet weather are conducive to fusarium infection. If the temperatures are above 32°C and it is hot and dry, the risk of fusarium infection is very low.

In 2009, a lot of spring wheat was planted 1 to 2 weeks earlier than most years. The crop will also be heading earlier than normal, depending on the planting date and the temperatures in June. In most parts of the province, spring wheat normally heads the last week of June or the first week of July. Start monitoring earlier planted fields for the risk of fusarium infection in mid-June.

Site-Specific DONcast

Deoxynivalenol (DON) is the toxin produced by the fusarium mould. To help predict the risk potential of fusarium and DON (in ppm), maps are available at www.weatherinnovations.com/DONcast.cfm. Site-Specific DONcast is a much more precise tool than the regional maps previously available. It is very important to monitor your own fields to identify the time of head emergence (Zadoks 59) in order to accurately run the Site-Specific DONcast calculator.

Fungicide Application

Proline® and Folicur® fungicides are currently the only products registered for fusarium suppression in spring wheat. To get the greatest suppression of fusarium, these products must be applied:

• at the correct growth stage of the wheat,
• with the correct nozzles to get proper wheat head coverage.

Growth Stage

The product should be applied when at least 75% of the wheat heads on the main stem are fully emerged (Zadok 59) to when 50% of the heads on the main stem are in the flower stage. Refer to Figure 1 - Representative Zadok Stages and Figure 2 - Flowering Stage.

Figure 1 - Representative Zadok Stages

Figure 2 - Flowering Stage

Nozzles

Research conducted by Helmut Spiecer and Dr. Dave Hooker at the Ridgetown Campus - University of Guelph concluded that the best nozzles to spray the wheat heads horizontally from the front and the back were the Alternating Turbo FloodJet nozzles (Photo 1). The nozzles should be 30 cm (12 in) above canopy and 15 degrees from horizontal (Photo 1).

The Twin Jet nozzles (Photo 2) give less coverage of fungicide product on the wheat head than the Turbo FloodJet, therefore significantly reducing the effectiveness of the product.

Photo 1 - Alternating Turbo FloodJet nozzles

Photo 2 - Twin Jet nozzles

Photos: David Hooker

Yield

On-farm trials with Folicur in spring wheat have shown an average of about 2.5 bushel per acre yield increase. A limited number of on-farm trials with Proline over the past two years have shown an average yield increase of 6 bushels per acre. Yield response will vary depending on the disease pressure at application time. Sprayer trampling when applying a fungicide is equivalent to about 1 - 1.5 bushel per acre.

Bottom Line

Proline® and Folicur® fungicides are applied at the correct growth stage of the wheat and with the correct nozzles to get proper wheat head coverage and greatest product suppression of fusarium. Anything less will dramatically reduce the amount of suppression of fusarium in spring wheat.