Date of this Version
36th Biennial Meeting of the American Society of Sugar Beet Technologists 2011 Albuquerque, New Mexico, USA, 2-5 March 2011
Rhizoctonia root and crown rot, caused by Rhizoctonia solani, is the most widespread, consistently found, and damaging sugar beet disease in Nebraska. It is capable of causing both a seedling disease and two different phases of root rot later in season. These two phases include a crown rot, and a tip rot of the tap root originating beneath the soil surface. Since there are several diverse forms (root rot phases) of the disease observed in Nebraska, it has been difficult to make fungicide recommendations based only on plant growth stage or chronological time of the season. In the attempt to determine more efficient application timings, a study was begun in 2009 with the purpose of making fungicide applications based on measurement of soil temperature. Spray treatments were applied when 10 cm soil temperatures averaged 15°, 18°, 21°, and 24°C for 3 sequential days, with two additional treatments consisting of untreated checks and spraying at symptom expression. Data collected included root disease incidence counts, sucrose and root yield, and sugar loss to molasses determinations. Sugar yields and numbers of diseased plants were significantly improved with the use of azoxystrobin when soil temperature reached 15°, 18° and 21°C, compared to controls and spraying after.