Root rot of sugarbeet in the Vojvodina Province

Abstract

Large changes introduced in the sugar beet production technology in the Vojvodina Province over last 40 years resulted in changes in the etiology and harmfulness of different agents of sugar beet root diseases. Improvements in cultivation practices reduced the harmfulness of some diseases while increased the harmfulness of others. Some disease agents became obsolete, but others gained importance. New agents of root diseases were found. The most frequent damages, persisting over long periods of time were caused by seedling damping-off, Fusarium root rot, charcoal root rot, parasitic (Rhizomania) and non-parasitic root bearding. The parasitic damping-off caused by several fungal species but most frequently by Phoma betae occurred at the time when multigerm seeds were used in combination with extensive cultural practices. The agents of seedling diseases completely lost their significance as the consequence of switching to fungicide - treated monogerm seeds, earlier planting and improved soil tillage. In the period of intensive use of agricultural chemicals, seedling damping-off occurred frequently due to the phytotoxic action of chemicals (insecticides, herbicides and mineral fertilizers). In some years, frosts caused damping- off of sugar beet seedlings on a large scale in the Vojvodina Province. Poor sugar beet germination and emergence were frequently due to spring droughts. Sometimes they were due to strong winds. The occurrence of Fusarium root rot and charcoal root rot intensified on poor soils. Fusariosis symptoms were exhibited as plant wilting and different forms of root rot. In recent years root tip rot has occurred frequently in the first part of the growing season causing necrosis and dying of plants. Lateral roots tended to proliferate from the healthy tissue, giving the root a bearded appearance similar to Rhizomania. Fusarium oxysporum was the most frequent agent of this fusariosis. F. graminearum, F. equiseti, F. solani have also been identified in recent years as the agent of root rot, but its importance was much lower. Charcoal root rot and plant wilting (Macrophomina phaseolina) have caused extensive damages in sugar beets, especially under the conditions of severe drought and high temperatures in summer. In some years, it was the dominant agent of root rot. Mixed infections caused by fungi from the genera Fusarium and M. phaseolina were encountered frequently. The extent of damage caused by these diseases was reduced by improved pro- duction technology. Rhizomania of sugar beet (caused by beet necrotic yellow vein virus) was identified in Serbia in the 1970s. Results of recent investigations have shown that BNYVV is widespread in Vojvodina, since the virus was found on 36,7% (24,674 ha) of acreages from 67,213 ha of total sugar beet acreages inspected on incidence of BNYVV in the period from 1997 to 2004 year. In the last few years, the occurrence of Rhizoctonia root rot (Rhizoctonia solani) was registered in some localities in Vojvodina.