Tips for Improving Cercospora Leaf Spot Control in Sugarbeets

Improve your Cercopora leaf spot control with timely fungicide applications, increased spray rates or pressure and not applying to wilted sugar beets.

Over half of Michigan’s beet acreage has been planted to susceptible leaf spot varieties. Season long control of leaf spot in these varieties is more difficult, but can be achieved if growers follow specific recommendations.

Systemic fungicides are more effective than contact materials. Start your spray program with the most effective materials. First application and reapplication timings for your area can be made following label guidelines or from the BEETcast website. Be sure to also scout fields starting about canopy closure or July 1. Check places with little or no air movement first (i.e. next to corn fields, woodlots, or creek bottoms). If the first Cercospora spot is visible anywhere in the field it is economically justified to begin the first fungicide application. Research indicates best timing of fungicide for both control and net revenue occurs just prior to the first spot being found. Timing of the first spray should never be delayed beyond the first spot in the field.

Coverage is critical with fungicide applications. Fungicides need to penetrate to the new growth in the plants crown. Recent Michigan Sugar research indicates water rates of 20 gallons per acre coupled with 100 to 120 PSI pump pressures (80-100 PSI at the nozzles) are best for efficacy, especially for protectants. An aerial (airplane) application can provide good protection with at least 5 gallon of water per acre.

Always apply fungicides to dry leaf surfaces; this will reduce the likelihood of run off. Do not spray “FLAT” (dry-wilted) beets. Control measures are normally justified until early-mid September, depending on environment and anticipated harvest date. Always rotate fungicide classes to prevent disease resistance.

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