THE INCIDENCE OF POLYMYXA-BETAE AND OTHER FUNGAL ROOT PARASITES OF SUGAR-BEET IN BRITAIN

A 2‐year survey of soils from a total of 208 fields, using sugar‐beet seedlings as bait plants, showed Polymyxa betae to be ubiquitous in the sugar‐beet‐growing areas of Britain. It was detected in some soils which had not grown a host crop for up to 17 years. However, infection of roots was relatively infrequent in plant samples taken from 134 survey fields in early summer and the density of colonization always low. Three other non‐mycelial fungi, Olpidium brassicae, Lagena radicicola and Rhizophydium graminis were also common parasites of sugar‐beet roots detected in soil bioassays. Infection of plant samples by O. brassicae was particularly severe. Copyright © 1990, Wiley Blackwell. All rights reserved