Considerations for foliar control of Rhizoctonia in sugarbeets

Timely foliar applications of Quadris fungicide can control Rhizoctonia root rot in sugarbeets.

Research conducted by Michigan State University Sugarbeet Advancement and Michigan Sugar Company indicates that a well-timed foliar application of Quadris on a susceptible variety can give up to 80 percent control of Rhizoctonia rot root in sugarbeets. Foliar applications should be applied in a 7-inch band targeting the crown of the plant. For rows with a 30 or 22-inch width, 10.5 or 14.3 ounce per acre rate is recommended, respectively.

Timing of application of Quadris can very each year according to the planting date, soil temperature, moisture and variety tolerance. Ideally, applications of fungicide should be applied just before or at disease infection. High infection periods occur as soil temperatures at the 4-inch depth approach 70 degrees and have free moisture. Soil temperatures are posted for each area on the Michigan Beets website.

Currently, in all of our sugarbeet growing areas, soil temperatures are 70 degrees and above. Because of late planting many of our beets are relatively small compared to other years. We would like to see a minimum of a 2-4 leaf stage for the first application. If Quadris was applied T-band in-furrow, a second application can be applied at about the 6-8 leaf stage for added control. Two foliar applications applied at the 2-4 and 6-8 leaf stage are very effective when utilizing a very susceptible variety when no in-furrow is applied.

Fields should be scouted regularly to monitor disease occurrence. If early season die off from Rhizoctonia is seen (approximately 8-16 leaf stage), a rescue treatment may be helpful. Applications should be banded directly in the crown and additional water may be beneficial. These treatments are never as effective as an in-furrow or well-timed foliar application. Quadris should not be broadcast because of reduced effectiveness. Also, no oil based insecticides should be added, as leaf injury will occur. Chelated micronutrients such as manganese are compatible and safely added to Quadris. Always check compatibility and label precautions when tank-mixing with Quadris.

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