If grass is green, soybean white mould is keen

Timing a white mould fungicide application in soybeans can be tricky business. The typical recommendation is to spray a first-pass fungicide at the R2 to R2.5 stage.

Most Ontario soybean fields, however, are highly variable and can contain plants progressing at different growth rates within the stand. How can you tackle this challenge? BASF technical development manager Rob Miller has a tip for growers who annually struggle to time their fungicide applications.

At the recent BASF Knowledge Harvest event held in London, Ont., Miller talked timing and the need to pay particular attention to the condition of their lawns during the Canada Day weekend.

Miller recommends growers start monitoring field moisture levels a week or two prior to the July 1st long weekend. The disease needs moisture to produce mushroom-like structures called apothecia that eject spores onto the soybean plant. The spores then land on flower petals leading to infection.

Then on the July long weekend it’s time to take a good look at your lawn. “On Canada Day if grass is green, white mould is keen,” says Miller. If grass is green the moisture that’s fuelling it is also likely supporting mould growth. If that’s the case it’s time to “decide which product might be the best fungicide to use and what might be your proper application timing.”

Miller notes that BASF will be launching a new fungicide product to control white mould for 2018. Cotegra was available last year in Western Canada for use on canola. In this interview, Miller explains that the fungicide will now be available in Eastern Canada for use on soybeans, canola, and dry beans. Cotegra combines two active ingredients and two modes of action – boscalid (Group 7) and prothioconazole (Group 3) – to target white mould in a convenient liquid premix.

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