Clubroot

Question 1

What crops does club root effect

Answer 1

Oilseed rape and all brassica species are affected e.g turnip and swede

Question 2

What weeds can also host club root

Answer 2

Charlock and shepards purse

Question 3

What is shepherds purse

Answer 3

Cruciferous weed

Question 4

What causes club root

Answer 4

Soul born pathogen called plasmodiophora brassicas

Question 5

How long can the pathogen survive in the soil

Answer 5

15 years

Question 6

What are the symptoms

Answer 6

Infected roots form clumsy falls which reduces nutrient/water uptake and lowers yield

Question 7

What’s happened recently in the uk to favour the pathogen

Answer 7

Recent warm wet weather favours the pathogen movement

Question 8

Yield losses ?

Answer 8

Yield losses are not significant at national level, 10% losses are common in OSR, can cause tota crop failure

Question 9

What used to control clubroot

Answer 9

Mercury chloride no longer in use

Question 10

What is available now to control it, how much ?

Answer 10

Spreading lime 8 t/ha reduces clubroot by 25%

Question 11

What micronutrient also helps to lower clubroot activity

Answer 11

Boron

Question 12

Name 3 clubroot resistant varieties (OSR)

Answer 12

Crome, crocodile and CrossFit

Question 13

How do you test for clubroot

Answer 13

Soil test prior to planting
Prioritise high risk areas- gates, field entrances, recently flooded areas
Test by growing bait plants in suspected areas

Question 14

How to sample

Answer 14

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

Question 15

Thresholds ?

Answer 15

Suggested thresholds have been set for veg brassicas but no validated thresholds for OSR

Question 16

Present controls ?

Answer 16

No present fungicides or bio- controls but the key is to understand pressures- restrict its spread, make informed rotational or varietial choices

Question 17

Early symptoms

Answer 17

The first symptoms occur 6-8 weeks after planting if soil is most and temp 15oC+
Roots swollen
distorted
irregular white galls which enlarge

Question 18

Later symptoms

Answer 18

Above ground symptoms appear much later on, causing stunting and yellowing.
Dry conditions- wilting especially if galling is severe

Question 19

What can you do if symptoms reach above ground

Answer 19

Use NDVI’s to detect and map infected areas to help guide management options and understand field factors which favour the pathogen

Question 20

What does NDVI stand for

Answer 20

Normalised difference vegetation index

Question 21

What’s the problem with persistently using resistant varieties

Answer 21

Likely increases the selection pressure on the pathogen population and may lead to new virulent strains which are able to infect previously resistant crops

Question 22

Rotations ?

Answer 22

Shorter rotations increase the soils clubroot inoculum burden

Question 23

Managing clubroot 4 factors

Answer 23

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