Distribution of violet root rot (Helicobasidium purpureum Pat.) of sugar beet and preliminary experiments on factors affecting the disease

Abstract

Examination of sugar beet grown in eastern England over the period 1936‐43 has shown that up to 5% of factory tarehouse samples contain roots infected with violet root rot. The results of the survey suggest that there are considerable areas where light attacks of the disease occur, as well as fields in which severe attacks develop when susceptible crops are grown. The disease occurred on roots grown in many types of soil but most frequently on those from light alkaline soils. It was found to reduce the sugar content and increase the dirt tare of sugar beet.The causal fungus, Helicobasidium purpureum, has a wide host range and observations suggest that it persists in the field on weeds, as severe attacks on cultivated crops often occur in weed‐infested fields. It also survives as sclerotia, which develop freely on the roots of susceptible crops. While the undisturbed soil conditions of leys and uncultivated land favour increase in infectivity, good cultural practices, trap cropping and application of nitrogenous fertilizers act as a check. These control measures will reduce infectivity even when applied to soil in which consecutive, susceptible crops are grown. Wet soil conditions did not favour the development of infection, and the frequent occurrence of the disease in wet places may be due to such soil conditions favouring survival of sclerotia.Experiments with compost made from factory waste showed that although the fungus can survive the process, its virulence was so reduced that there is no likelihood that use of such compost would lead to severe violet root rot infection.