Controlling Cercospora leafspot in sugarbeets

Utilize BEETcast and management guidelines for controlling Cercospora leafspot for Michigan sugarbeets.

Cercospora leafspot is the most serious foliar disease in sugarbeets in the Michigan growing region. If not managed properly, leafspot will reduce both tonnage and sugar content. Research trials conducted by Michigan Sugar Company has shown reductions of net revenue up to $120 per acre if left uncontrolled. Significant progress has been made in controlling Cercospora in Michigan with the introduction of new fungicides and utilizing the BEETcast prediction model.

The single most important Cercospora leafspot fungicide spray is the first application. Research indicates best timing of fungicide for control and net revenue occurs just prior to the first spot being found. Timing of the first and subsequent fungicide applications should be applied according to BEETcast disease severity values (DSV) for your management zone andvariety tolerance. Growers can access the BEETcast model and spray recommendations on the website www.MichiganBeets.com. Timing of first spray should never be delayed beyond the first spot being found in the field.

Even though spring planting and row closure of sugarbeets is significantly delayed, growers are encourage to stay the course according to BEETcast spray recommendations. There are several reasons for this recommendation. Favorable environmental conditions and infection can occur even though plants are small. In 2010, the Michigan growing region experienced its worst leafspot outbreak in several years. We would expect the potential inoculum levels to be high in 2011. Michigan has planted a high percentage of its crop to very susceptible leafspot varieties. Sugar price is high and economics of fungicide applications is positive. Many producers who tried to second guess the BEETcast model in 2010 suffered a large economic loss.

Remember, fungicides classes should always be rotated. Ideally, do not use any chemistry more than once in a leafspot spray program. If Quadris is used at the 4 leaves or later stage for Rhizoctonia control, apply a triazol fungicide for the first leafspot spray. To reduce the chance of Cercospora developing further fungicide resistance, fungicides can be tank-mixed with unrelated types of compounds such as EDBC, Tins or copper. Always scout fields in conjunction with the BEETcast spray model. Follow labeled directions for pre-harvest intervals.

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