Clubroot Flashcards
What crops does club root effect
Oilseed rape and all brassica species are affected e.g turnip and swede
What weeds can also host club root
Charlock and shepards purse
What is shepherds purse
Cruciferous weed
What causes club root
Soul born pathogen called plasmodiophora brassicas
How long can the pathogen survive in the soil
15 years
What are the symptoms
Infected roots form clumsy falls which reduces nutrient/water uptake and lowers yield
What’s happened recently in the uk to favour the pathogen
Recent warm wet weather favours the pathogen movement
Yield losses ?
Yield losses are not significant at national level, 10% losses are common in OSR, can cause tota crop failure
What used to control clubroot
Mercury chloride no longer in use
What is available now to control it, how much ?
Spreading lime 8 t/ha reduces clubroot by 25%
What micronutrient also helps to lower clubroot activity
Boron
Name 3 clubroot resistant varieties (OSR)
Crome, crocodile and CrossFit
How do you test for clubroot
Soil test prior to planting
Prioritise high risk areas- gates, field entrances, recently flooded areas
Test by growing bait plants in suspected areas
How to sample
Samples- monitor roots over winter, when the field is easier walked, use tramlines to create sample grid, samples should be no more than 50m apart and pull up 10 plants at a time to inspect
Thresholds ?
Suggested thresholds have been set for veg brassicas but no validated thresholds for OSR
Present controls ?
No present fungicides or bio- controls but the key is to understand pressures- restrict its spread, make informed rotational or varietial choices
Early symptoms
The first symptoms occur 6-8 weeks after planting if soil is most and temp 15oC+
Roots swollen
distorted
irregular white galls which enlarge
Later symptoms
Above ground symptoms appear much later on, causing stunting and yellowing.
Dry conditions- wilting especially if galling is severe
What can you do if symptoms reach above ground
Use NDVI’s to detect and map infected areas to help guide management options and understand field factors which favour the pathogen
What does NDVI stand for
Normalised difference vegetation index
What’s the problem with persistently using resistant varieties
Likely increases the selection pressure on the pathogen population and may lead to new virulent strains which are able to infect previously resistant crops
Rotations ?
Shorter rotations increase the soils clubroot inoculum burden
Managing clubroot 4 factors
clubroot zoospores spread through wet compact soils - Keep field well drained- increases workability.
Good machinery hygiene between fields- spreads through OM.
Keep soil above pH 7- calcium at drilling
Control weeds
