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Management of clubroot (Plasmodiophora brassicae) in winter oilseed rape

HGCA PROJECT REPORT 487 

Management of clubroot (Plasmodiophora brassicae) in winter oilseed rape


by
Fiona Burnett1, Peter Gladders2, Julie A Smith3 and Chris Theobald4

1SRUC, West Mains Road, Edinburgh EH9 3JG
2ADAS Boxworth, Battlegate Road, Cambridge CB23 4NN
3ADAS Rosemaund, Preston Wynne, Hereford HR1 3PG
4Biomathemativs & Statistics Scotland (BioSS) and School of Mathematics, University of Edinburgh, James Clerk Maxwell Building, Mayfield Road, Edinburgh EH9 3JZ

Abstract

Clubroot is an increasing problem in oilseed rape crops throughout the UK and has been exacerbated by close rotations, as the disease can persist for upwards of 15 years in soils. The galls on roots formed by the clubroot pathogen, Plasmodiophora brassicae, affect normal root function and reduce the uptake of water and nutrients such that even low levels can reduce yield. Root galls will commonly breakdown with secondary rots such that root function is seriously impaired.

Yield losses to clubroot in this project were 0.3 t/ha for every 10% clubroot severity. Losses in affected crops can therefore equate to over 50% of potential yield in the most severely infected crops. Survey work in this project, for the years 2007-2009 showed that the disease was present in all areas of the UK where oilseed rape was grown. Of the sites surveyed, 52% tested positive. The sites sampled were not randomly selected and growers and agronomists who participated tended to select fields of concern. These positive test results were often at sub clinical levels in the crop.

An aim of the project was to investigate the use of varietal resistance and /or soil amendments, Calcium carbonate (LimeX70), Calcium cyanamide (Perlka) and boron (Solubor) to manage clubroot in affected fields. Soil amendments gave variable control but showed some potential as part of a clubroot management strategy. Varietal resistance remained the more effective management tool for growers, but varietal resistance is under pressure at sites where it has been heavily used in back rotations and varietal control was not effective at sites in Aberdeenshire. The varieties Mendel and Cracker, gave 50 - 95% disease control at three sites in the West Midlands. Control with soil amendments ranged from 0 - 90% but analysed over the trial series control meaned at 25% for the best solo treatment (Calcium carbonate at 8 t/ha). The Calcium cyanamide product is no longer supported for use on oilseed rape crops in the autumn in the UK. Soil testing for clubroot and soil pH, and lengthening rotations are important to the long term management of clubroot on farms, as varietal resistance and soil amendments give inconsistent results

Project Number : 3373

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