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Transcript of Clubroot management strategies for brassica production Aaron Heinrich and Alex Stone Dept. of...
![Page 1: Clubroot management strategies for brassica production Aaron Heinrich and Alex Stone Dept. of Horticulture.](https://reader030.fdocuments.in/reader030/viewer/2022032723/56649d155503460f949ea173/html5/thumbnails/1.jpg)
Clubroot management strategies for brassica production
Aaron Heinrich and Alex StoneDept. of Horticulture
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It’s called clubroot for a reason…
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Hosts
And more…Susceptibility varies by species and cultivar
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Clubroot’s impact“In the past 3 years [2009-12] we have had a 25% loss in our brassica crops due to clubroot, costing us between $60-80K/year. We are running out of clubroot free ground on which to rotate brassica crops.”
“In 2013 we experienced a 30 to 50% loss in 5 of our highest yielding brassica crops this year totaling $20K. Three years ago we played out this scenario knowing that our future looked quite bleak... We need to figure out a way to grow brassicas in fields that have a high clubroot population.”
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Is incidence increasing?
1. Increase in radish and turnip cover crop seed2. More farms with 15+ year history of short
rotations (<4 yrs)3. Increased brassica production to meet
demand4. More overwintering brassica crops
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Disease cycle
Disease severity affected by:1. Moisture2. Temperature3. Low soil pH4. Spore density
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Management strategies
1. Rotation– 5 to 7 years out of brassicas
2. Sanitation3. pH manipulation– lime to pH ≥7.0
4. Boron?5. Biologic controls?6. Resistant cultivars?7. Water management
Control not eradication is the goal
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Management strategies
1. Rotation– 5 to 7 years out of brassicas
2. Sanitation3. pH manipulation– lime to pH ≥7.0
4. Boron?5. Biologic controls?6. Resistant cultivars?7. Water management
Control not eradication is the goal
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Liming success in California
• 1978 clubroot first identified• Started aggressive liming program• Still present but controlled
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2012 clubroot survey
Response from 19 of 37 farmers• 83% had used lime as a control– 21% aimed for pH ≥6.8– 52% verified if target pH reached– 26% said liming helped
Is liming effective in western Oregon?Are farmers liming “correctly”?
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2014 Greenhouse study: Cauliflower
ControlpH= 5.7Infection rate: 100%Avg plant wt: 0.3 g
LimedpH ≥ 7.1Infection rate: <4%Avg plant wt: 0.8 g
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2014 Greenhouse studies: cauliflower
Control Serenade Boron (10 lb/A)
Lime Lime
5.7 5.7 5.7 6.3 7.1
0
20
40
60
80
100
5 rating
4 rating
3 rating
2 rating
1 rating
Infe
ctio
n r
ate
and
sev
er-
ity
(%)
Dead/dying
Minor clubs on laterals
1. Serenade not effective 2. Boron reduced severity but not infection rate3. Increasing pH from 5.7 to 6.3 slightly effective4. pH >7.0 highly effective
pH
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2014 Field studies: broccoli & kale
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2014 Field studiespH 6.7
pH 7.3
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2014 Field studies: Lacinato Kale
No lime Lime6.7 7.3
0
10
20
30
40
50
60
70
80
90
100
Rating 3
Rating 2
Rating 1
Infe
ction
rate
and
se
verit
y (%
)
No lime lime0
50
100
150
200
250
300
350
400
450
Plan
t wt (
g)
In 3 field trials:• 44-77% reduction in infection rate• 74-90% reduction in disease severity• Serenade and B (4 and 8 lb/A) not effective in these studies
>50% clubbed<50% clubbedclubs on laterals
pH
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Why is there a difference between greenhouse and field studies?
Treatment pHInfected
plants (%)Control 6.0 91Limed (field mixed) 7.0 34Limed (sieved/mixed) 7.0 6
(Adapted from Dobson et al., 1983)
Clubroot field trial: western WA
Same pH, different infection rate
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Importance of uniform soil mixing
Treatment pHInfected
plants (%)
Microscale pH variability
(pH unit)Control 5.9 100 0.7Limed (field mixed) 6.4 86 1.1Limed (sieved/mixed) 6.5 25 0.3
(Adapted from Dobson et al, 1983)
Clubroot greenhouse trial
Under field conditions, 100% clubroot control highly unlikely with liming.
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Implementing a successful clubroot liming program
Steps:1. Estimate lime requirement2. Choose lime material3. Apply at correct time4. Incorporate thoroughly 5. Measure soil pH
Target pH ≥ 7.0
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Step 1: Estimate lime requirement1. Use SMP buffer test and OSU pub. EM 9057 to
raise pH to ~6.7 (6” incorporation depth)2. Multiply SMP buffer rate by 1.5-2.0 to increase pH
>6.7
0 1 2 3 4 5 6 75.96.16.36.56.76.97.17.37.5
ton lime/acre
SMP Buffer
1.5-2.0 x SMP Buffer
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Step 2: Choose lime material
Product Form Cost material only ($/ton)
Microna Ag-H2O Powder 210
Microna Access Powder 105
Ash Grove Ag lime Powder 60
CalPril Prilled 260
Microna Garden Pearls Prilled 392
Most reactive
Least reactive
Most economical, similar performance
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Using pelleted limeAdvantages– Easy to handle
Disadvantages– Expensive – Less reactive (i.e.
requires higher rates)– Requires additional steps
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Using pelleted lime efficiently If incorporated too soon, the pellets will not disperse!
Option 1:– Broadcast – Apply irrigation (or wait for rain)– Till
Option 2:– Broadcast – 1st tillage – If sufficient moisture, no irrigation needed– 2nd tillage
1.5 minutes
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Step 3: Apply at correct timeApply 1 wk minimum before planting
0 1 2 3 45.6
5.8
6.0
6.2
6.4
6.6
6.8
7.0
7.2
Ash Grove (3 t/a)Microna Ag H2O (3.1 t/a)Microna Access (3.0 t/a)Cal Pril (3.3 t/a)Garden Pearls (3.6 t/a)
Weeks after application
pH
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Step 4: Incorporate thoroughly
Treatment pHInfected
plants (%)
Microscale pH variability
(pH unit)Control 5.9 100 0.7Limed (field mixed) 6.4 86 1.1Limed (sieved/mixed) 6.5 25 0.3
Clubroot greenhouse trial
(Adapted from Dobson et al., 1983)
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Step 5: Measure soil pH
Soil sample!• Verify if target pH
reached
Caution: if you can see unreacted lime, the soil test pH may be higher than what the plants are experiencing!
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Integrated Clubroot Management
• Scouting• Rotation (4-5+ yrs)• Maintain soil pH ≥6.8• Plant resistant varieties• Irrigation management
No one strategy is enough!
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Acknowledgements
We thank our farmer partners for their collaboration as well as the following organizations for funding this project:
The Agriculture Research FoundationOregon Processed Vegetable Commission