No abstract

Azoxystrobin is applied early in the sugar beet growing season in north-central United States for control of Rhizoctonia damping-off and Rhizoctonia crown and root rot caused by Rhizoctonia solani anastomoses groups (AGs) 4 and 2-2, respectively. Fungicide application timings based on crop growth stage and soil temperature thresholds were evaluated in inoculated small-scale trials and in commercial fields with a history of Rhizoctonia crown and root rot. Soil temperature thresholds of 10, 15, and 20°C were selected for fungicide application timings and used to test whether soil temperature could be used to better time applications of azoxystrobin. In both small- and large-plot trials, timing applications after attainment of specific soil temperature thresholds did not improve efficacy of azoxystrobin in controlling damping-off or Rhizoctonia crown and root rot compared with application timings based on either planting date, seedling development, or leaf stage in a susceptible (E-17) and a resistant (RH-5) cultivar. Application rate and split application timings of azoxystrobin had no significant effect on severity of crown and root rot. Other environmental factors such as soil moisture may interact with soil temperature to influence disease development. Cv. RH-5 had higher sugar yield attributes than the susceptible cultivar (E-17) in seasons conducive and nonconducive to crown and root rot development. All isolates recovered from both small- and large-plot trials in all years were AG 2-2. R. solani AG 4 was not identified in any samples from any year.

No abstract

Respiratory losses in sugar beets as a function of storage temperature, field nitrogen application, sprouting incidence and handling severity. The trend toward warmer temperatures in Michigan has lead to an increased risk of excessive temperatures in field piles of sugarbeets. In the 2004-2005 season, the Michigan industry is estimated to have lost approximately $25,000,000 to pile breakdown following an unusually warm winter and spring. Determination of optimal storage strategies requires knowing the effects of the major factors influencing respiratory activity. From 2005 to 2009, we evaluated the impact of storage temperature, nitrogen applied during the growing season, and handling severity on respiration after one and four months holding. In addition, the contribution of sprouts formed during storage to respiratory activity was estimated by harvesting sprouts and measuring their respiratory activity relative to the root. Field nitrogen application between 0 and 160 lb/acre did not influence respiratory activity. Commercial machine harvesting increased respiratory activity between 10 and 25% relative to handharvested controls and the impact of machine harvesting increased with storage duration. Beets collected after dropping into full, half-full and empty trailers all experienced enhanced respiration, with the greater respiratory activity induced by the most damaging treatment. The data collected will be used to model respiratory activity and pile temperature profiles for fieldstored sugarbeets in Michigan.

Headline is an effective fungicide for controlling Cercospora leafspot. It has also been promoted as a yield enhancer beyond its effect as a fungicide. Some farmers use Headline for this yield improvement on other crops, and a benefit has been found to Headline on sugarbeets in some research in other areas. Michigan Sugar Company has tested this claim for four years and Sugarbeet Advancement tested two locations for one year. Methods:Michigan Sugar Company research compared Headline to Eminent, and other Strobilurin fungicides, for four years and to an untreated check two of the years. Cercospora was controlled with Super Tin and Topsin plus Penncozeb applications as needed. The treatments were applied as an extra application not needed to control Cercospora. Fungicides used the first three years