Ten key components for higher sugarbeet quality – Tip #8

Controlling Cercospora leaf spot and maintaining healthy sugarbeet foliage is one of the ten keys to improve sugarbeet quality.

Maintaining healthy, disease-free foliage until sugarbeets are harvested is critical to maximizing sugar content and yield. More than half of Michigan’s sugarbeet acreage is planted to susceptible Cercospora leaf spot varieties. Controlling this disease is further complicated by the development of resistance to strobilurin fungicides (Headline and Gem) found in all Michigan sugarbeet growing areas in 2012. Left uncontrolled, this disease can reduce sugar content between one-half and 2 percentage points, depending on how early the disease is established. An aggressive fungicide spray program must be implemented season-long to prevent sugar loss.

The first spray is critical in setting the foundation for a successful leaf spot program. Research has shown that the best program will start applications before the first spot is seen in your field. Spraying after the first spot is considered late. The timing of the first spray each year can vary. Growers should utilize advice from Michigan Sugar Agriculturists and the BEETcast website www.MichiganBeets.com for best timing. All fungicide applications should be applied according to the Cercospora leaf spot resistance management program developed by the Michigan Sugarbeet Research Education Advisory Council (REACh).

All leaf spot fungicides should be tank-mixed with alternative modes of action. Follow recommended spray intervals on the label or shorten according to BEETcast/REACh recommendations. These may vary depending on the management zone you are in and the resistance of the variety. Make sure fungicide classes are alternated and never use a triazole fungicide back-to-back, even if the applications are tank-mixed. Also, do not use triazoles more than twice per season. Common tank-mix partners are EBDC’s and coppers. The chance for resistance to EBDC’s and coppers is low and they can be used back-to-back and for multiple applications in a season. Use 20 to 25 gallons of water with a minimum of 90 PSI for complete coverage. Spray coverage is absolutely critical when using contact or protectant type fungicides.

Another fungicide product that has shown to be very effective in Michigan Sugar trials is Super Tin. It is classified as an organometallic fungicide and is a protectant type. This means it is not absorbed in the leaf and will stay on the leaf surface. This product is used extensively in the Red River Valley. According to a recent survey conducted by Michigan State University Extension, this product is gaining in popularity and about 17 percent of Michigan growers used it in 2012. It is projected that about 35 percent will be using it in 2013. This product can be mixed and applied safely by following the product label. Growers that feel strobilurins are no longer effective should consider this as a good replacement.

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