The Effect of Plant Parasitic Nematodes, Rainfall and Other Factors on Docking Disorder of Sugar Beet

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Abstract
SUMMARY: In the years 1963 to 1972 the area of sugar beet in England reported affected with Docking disorder ranged from 174 to 7,819 ha. The disorder was most widespread after heavy May rainfall. Trichodorus spp. and Longidorus spp., which cause the primary damage to seedling roots, were common in sites prone to the disorder and surveyed between 1968 and 1971. Nematode numbers in soil samples taken from these sites at drilling could not be correlated with subsequent yield or root shape. Of the surveyed sites, 104 showed no symptoms of Docking disorder (average root yield=44·5 tonnes/ha), 44 showed symptoms early in the season but these disappeared later (average root yield=34·5 tonnes/ha) and 40 showed persistent symptoms (average root yield=27·0 tonnes/ha). Root shape was worst in sites with persistent symptoms. Docking disorder was impossible to predict accurately because the damage is influenced by growing conditions but it was more likely to be severe in fields with a previous history of the disorder.