By Steven Poindexter,
The incidence of Cercospora leaf spot and Rhizoctonia root rot has been relatively low in the Michigan sugarbeet growing region for 2013. A combination of late planting, dry and cool summer conditions and good timing of crop protection materials has minimized disease infections. However, in previous years with prolonged dry periods in the fall, powdery mildew has developed in grower’s fields and Michigan State University Extension Sugarbeet Advancement trials. Heavy infestations of powdery mildew can reduce photosynthesis and make leaves more frost susceptible.
Triazole and strobilurin fungicides are effective at controlling powdery mildew. Growers that used one of these fungicides in September for Cercospora leaf spot control are not likely to have a large issue with powdery mildew.
Growers in Michigan overall have done an excellent job with timely applications of leaf spot fungicides. Tank mixing has also added an additional level of protection along with helping in fungicide resistance management. This summer also included cooler nights and lower than normal precipitation. These conditions are less than ideal for disease establishment. Late spring planting of sugarbeets also was a factor, giving us a shorter growing season and less of the more susceptible older leaves. The combination of all these factors has allowed us up to this point to have good healthy leaves.
Rhizoctonia root rot was also less than previous years. Management of this disease has increased with about half of our producers utilizing an in-furrow application of Quadris followed by a second spray at the 6-8 leaf stage. It is estimated that 90 percent of our beet acres have one or more applications. Producers have also been very strategic in putting Rhizoctonia resistant varieties in high inoculum fields. On an environmental note, a cooler dryer summer season was also helpful in reducing infections. Most of the Rhizoctonia we currently see on beets is from below ground soil infections. A few years ago crown rot infections where more common.