Management of Rhizoctonia Root and Crown Rot of Sugarbeet
(PP1495, 11月11日修订. 2021)Rhizoctonia root and crown rot is one of the most severe soil-borne diseases of sugarbeet and it’s a major problem for growers in Minnesota and North Dakota.
The local sugarbeet-growing areas have been in a wet cycle during the past 20 years. Fields with high disease severity probably have resulted from a combination of wet conditions and a prevalence of other susceptible host crops in the rotation. 例如, nonsusceptible crops such as wheat and barley formerly used in rotation with sugarbeet have decreased in acreage and have been replaced with susceptible crops such as soybeans, 食用豆类和玉米.
Rhizoctonia root and crown rot may reduce yield significantly and diseased roots may cause problems in storage piles. Growers at some sugar cooperatives are required to destroy fields with more than a 50 percent incidence of root rot because infected roots cannot be placed in piles for-long term storage.
疾病的症状
The most common symptom is wilting of the leaves, 从最老的叶子开始, and is likely a consequence of damage to the vascular system
(图1及3). 叶子可能变黄，也可能不变黄. 在某些情况下, the petioles may develop some blackening where they are attached to the crown (图2).
根在土线以下
Crown rot infection probably is initiated when infected soil is thrown into crowns during cultivation, by rain splash of infected soil into the crowns or where the petiole attachment to the crown is covered with infected soil (图2). Root rot infection typically starts at or just below the soil line (图3), and sometimes lower on the tap root (图4).
Root rot symptoms may range from scattered brown to black lesions on the root surface to complete rotting of the root. Initially, the disease may occur in a few patches in a field. 如果有明显的接种, often as a result of continuous planting of susceptible hosts, entire sugarbeet fields may be lost to the disease when conditions are favorable for disease development.
