Rhizoctonia root rot of sugarbeets is one of the most damaging root diseases in Michigan. Yields can be reduced up to 10 tons per acre and sugarbeet quality can be greatly affected. Corn, soybeans and dry edible beans are all hosts for Rhizoctonia, leaving it difficult to lower inoculum levels. Crop rotations with sugarbeets following wheat or wheat and clover may be helpful. Sugarbeet varieties with good resistance to the disease should be considered on fields with a chronic history of the disease.
Research over the last 10 years from Michigan State University Sugarbeet Advancement program and Michigan Sugar Company has shown that Rhizoctonia can be effectively controlled with proper placement and timing of Quadris fungicide. Growers who are planting very susceptible varieties, including the nematode-resistant variety, should consider either one or two fungicide applications depending on the suspected severity of the disease. Applications can be made either as a foliar or a T-band in-furrow application. Many growers are using a combination of the two with very effective results.
In-furrow T-band applications are very effective, economical, and can offer protection from both the seedling and root rot phase of the disease. The standard T-band width of 7 inches has worked well, but research has shown band widths of 3 to 4 inches have had similar effectiveness. This application is very economical because the Quadris rate is reduced proportionately to the band width. Growers that were using 10.5 ounces of Quadris in a 7-inch band are now using 5 to 7 ounces in a 3- to 4-inch band. In-furrow application takes the guess work out of timing a foliar application.
All foliar applications should be applied in a 7-inch band or less. The best timing of applications can vary depending on environmental factors including soil moisture and temperature. Work conducted by MSU Sugarbeet Advancement in the last three years has shown foliar applications at the 6 to 8 leaf stage have been much more effective than earlier timings. When heavy disease pressure is present, the combination of in-furrow and 6 to 8 leaf stage offers longer and improved efficacy..