Differentiation of the Disease Caused by Aphanomyces cochlioides and Girth Scab on Sugar Beet Roots - a Review

Severe symptoms of root rot on sugar beet have been observed in Poland and Germany since 2001. The symptom classification suggested girth scab as it was mistakenly classified on the basis of current classification, e.g. in LIZ. However, the cause of the disease was Aphanomyces cochlioides infection, not Streptomyces spp. According to these findings we cannot call the symptoms caused by A. cochlioides as 'girth scab'. The typical scab (girth scab) symptoms can be promoted by A. cochlioides infections. In many cases, A. cochlioides developed at the beginning of the season, during the seedling stage. Its further development was due to rainfall and was not routinely recognised in disease-changed tissues if in the middle of the summer the rainfall level was reduced. According to the described findings, renewed description and differentiation of the girth scab symptoms caused by Streptomyces spp. and root rot caused by A. cochlioides on sugar beet roots are suggested. Typical symptoms of the disease caused by A. cochlioides occur mainly on the upper part of the root but can also occur on its lower part, if weather conditions are favourable for the pathogen. The coexistence of A. cochlioides and Pythium spp. in the same niches is also possible. Currently the illustrations showing these symptoms are included in the 'girth scab' descriptions.