2015 Sugarbeet Cercospora leaf spot fungicide applications could start early

Cercospora leaf spot fungicide applications to sugarbeets may need to start earlier than normal because of environmental conditions and growth stage.

Timely planting, excellent emergence and favorable soil moisture conditions have the 2015 Michigan sugarbeet crop off to a great start. Plant growth has been excellent and root diseases have been minimal. A significant portion of the sugarbeet crop will be canopied by June 20, the longest day of the year. Early canopies and higher than normal BEETcast Disease Severity Values (DSVs) may indicate a need for growers to apply crop protection fungicides before July 1.

Michigan State University Extension has shown a well-timed first application is critical for setting the foundation for effective Cercospora control. It should be applied just prior to the first spot being seen in the field. BEETcast is a very effective tool to help grower’s time fungicide application throughout the season. Depending on the BEETcast risk management zone and variety susceptibility, first applications may start as early as 45 DSVs. In some areas, this may occur prior to July 1 this year. Growers in the “Red Zone” with a susceptible variety may want to consider an EBDC application as early as 35 DSVs. Then continue season-long interval sprays starting at 50-55 DSVs and continuing through Sept. 15. Length of spray intervals may vary depending on the label and management zone.

Documented strobilurin and benzimidazole fungicide resistance has been confirmed since 2011. Depending on the level of resistance, these products will not be reliable in controlling disease and should never be applied alone. To help slow down resistance to other classes of fungicides, producers will need to follow these guidelines.

  • Always rotate fungicides classes. Ideally, do not use any chemistry class more than twice.
  • Tank-mix triazoles, strobilurins, Tins and benzimidazole every time with an EBDC or copper. EBDCs or copper can be tanked-mixed every time.
  • Do not reduce fungicides rates, always use at suggested rate.
  • Spray fungicides at recommended spray intervals according to label or recommended BEETcast DSVs.
  • Use 20-25 gallons of water with a minimum of 90 PSI. Use surfactants or additives according to product label.
  • Spray all fungicides as a preventative program, there are no curative fungicides for Cercospora leaf spot.

One fungicide that is widely used in other sugarbeet growing areas and has very good efficacy are Tin-type products including Super Tin, Agritin and Minerva Duo. Minerva Duo is a new premix fungicide combining Tin with tetraconazole (Eminent). The Tin fungicide group is currently underutilized in the Michigan growing region. These fungicides are our most effective contact materials and offer a completely different mode of action for Cercospora leaf spot control. This mode of action will become increasingly important to help prevent resistance to the triazoles. The product can be applied safely if you read and follow labeled directions.

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