Integrated Management of Vegetable Diseases and Soil Health

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Integrated Management of Vegetable Diseases and
Soil Health
Frank J. Louws Professor and Extension Plant
Pathologist Department of Plant Pathology North
Carolina State University Raleigh
NC frank_louws_at_ncsu.edu
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Soil Health
Chemical Physical Biological
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Ecosystem Services

• PRODUCTION FUNCTION
• - supply and retention of nutrients
• - disease and pest suppression
• RESISTANCE TO STRESS/CAPACITY TO CHANGE
• - resist and recover from disasters
• - flexibility to adapt to different land uses
• BUFFER AND REACTOR FUNCTION
• - decomposition, mineralization, C-cycling
• - attenuation (e.g. of harmful pollutants)
• - absorb, retain, release, transport water
• HABITAT FUNCTION
• - structural, genetic and functional biodiversity

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Less reliance on external inputs More reliance
on Biology Processes and Cycles Knowledge and
Information
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DISEASE CONTROL What is the core component of
your program?
PESTICIDES
MANAGEMENT
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PRACTICE Crop Rotation practiced for
thousands of years Spatial, temporal, genetic
deployment of crops SCIENCE Understanding the
mechanisms - e.g. mechanisms associated with
fertility and decreased inoculum load The
Practice can direct the Science and the Science
can inform the Practice
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Science Common Sources of Inoculum
Soil Invader
Soil Inhabitant
Napoleon Know Your Enemy .Know Your
Friends
From G.N. Agrios. 2005. Plant Pathology. 5th
edition. Elsevier AP.
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Phytophthora capsici (crown and root rot)
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Crown and root rot management Water management
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Challenges with Managing Soilborne Diseases

• Microscopic difficult to sample and monitor
  (scouting)
• Patchy distribution
• Persistent and responsive inoculum (thresholds)
• Complex of pathogens that act together
• Generally requires prophylactic control not
  reactive

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COMPLEXITY OF FARMING SYSTEMS
Disease suppression Plant health
Rotation
Ecosystem Services
Farming system
RESEARCH EXTENSION TEACHING PRODUCTION
Biodiversity
Crop Diversity Genetic diversity Microbial
community analysis
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Plant 15 Sep 15 Oct
Prepare land and fumigate (15 Aug 15 Sep)
Manage Oct - Mar
Harvest Apr Jun And start over.
20,000 30,000 lb/A 22,000 - 32,000 kg/ha
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Plymouth Fernandez and Louws Experimental
Design Camarosa RCBD 4 replications Three-bed
plots Three year study (no rotation) Harvest
center row
Tactic Substitution
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Plymouth 2000-2002 Strawberry Yield Results
d
No Fumigant
cd
30000
cd
cd
cd
Telone II
bc
25000
MS drip
ab
a
20000
MB-C
Marketable Yield lb/A
MS shank
15000
Telone-C35
10000
InLine (1,3-D)
InLine
No Fumigant
Chloropicrin
Telone-C35
MS-shank
Telone-II
MS-drip
MB-C
5000
Chloropicrin
Fernandez Louws
0
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ON-FARM-TRIALS(usually replicated with 2-4
alternatives)Finding the holes making it work
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Bunn NC 2007
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HortTechnology 18705713
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Tomatoes Economic Analysis of Alternatives
(Sydorovych et al. HortTechnology 2008)
Over 9 years of trials
Net return of MeBr 8,758/A 21,641/ha
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T-C35 to maintain yields in plasticulture
tomatoes
Ecosystem Services
Farming system
A B X
Biodiversity
Important short term
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Tomatoes Tactic Diversification
Tube Grafting
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Tomatoes Tactic Diversification

• Ralstonia solanacearum
• Southern Bacterial Wilt
• Colonizes Vascular tissue
• Tropical Environments
• Soil Inhabitant
• Wide host range

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2007 Organic Farm TrialBacterial Wilt Management
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Vegetable and strawberry production systems are
inherently counter productive to soil health
management you have to start somewhere and
WHO better than YOU?... Soil Health is a
directional concept
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Practitioner Approach Can we implement a
compost-based production system and improve soil
health as an alternative to methyl bromide? JUST
DO IT!

• John Vollmer
• on farm research
• organic transition
• Michelle Grabowski
• MS student

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Controlled Microbial Compost

• Management intensive system
• Compost pile monitored and adjusted daily for
  temperature, moisture and CO2 content

Recipe 30 Dairy manure 30 Waste Hay 30
Waste Silage 5 Finished compost 5 Clay
soil
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Legume-Grass Cover Crop
Year 1 30 yd3/acre Year 2 20 yd3/acre Year 3
15-20 yd3/acre
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Rotary Spader
Raising of the Beds
Crop Establishment
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Marketable Yield



Indicates yield is significantly different than
MB
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Microbial Ecology
Strawberries - Tactic development

• Q Can we modulate microbial communities to
  suppress disease and/or enhance strawberry
  yields?
• Leandro, L. F.S., L.M. Ferguson, F.J. Louws, and
  G.E. Fernandez. 2007. Strawberry growth and
  productivity in fumigated compared to
  compost-amended production systems. HortScience
  42 227-231.
• Leandro, L.F.S., T. Guzman, L.M. Ferguson, G.E.
  Fernandez, and F.J. Louws. 2007. Population
  dynamics of Trichoderma in fumigated and
  compost-amended soil and on strawberry roots.
  Applied Soil Ecology 35237-246.

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• Disease suppression
• Plant growth promotion
• Good Yields
• Weed suppression
• Nutrient cycling
• Increased CEC
• Increased aggregate stability

A B X
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GOAL Design Suppressive Soils - Soils that
reduce or completely suppress the development of
soilborne plant diseases
Resource Availability
Competition Antibiosis
Root Pathogens
Beneficial Microbes
Hyper-parasitism
Nutrient cycling SAR ISR PGPR
Disease incidence severity
Plants
Microbially mediated mechanisms are critical
Abiotic causes may be important What drives the
structure of microbial communities?
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• Actinomycetes e.g Streptomyces spp

Linda Kinkel et. al. Green manures pathogen
suppression streptomyces antibiotic production
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Trichoderma
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SCHEMATIC DIAGRAM OF SYSTEMIC ACQUIRED RESISTANCE
(SAR) and INDUCED SYSTEMIC RESISTANCE (ISR)
III. When a pathogen lands on the (e.g.) leaf, it
cannot successfully establish a parasitic
relationship - infection is aborted.
II. A signal moves from the roots to the shoots
or other roots causing the distant tissue to
mount a defense response.
I. Beneficial bacteria colonize root inhabit
rhizosphere
May also get PGPR effects
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What drives the structure of microbial
communities? Soil typeCropping
HistorySeasonal/Yearly (Temporal)
impactsFarming Systems
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Cropping History Effect
Shuijin Hu et al. unpublished
High diversity soil
Low diversity soil

• Microbes dominated the disease suppression
• Potential importance of Microbial Diversity
  (general suppression)
• P Pythium ultimum STM steam sterilized

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Cropping History Effect Diverse Soils with
Organic History
High soil labile C correlated with high pathogen
density
Shuijin Hu et al. unpublished
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Seedling mortality negatively correlated with
microbial diversity
Hu et al. unpublished
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What Drives Microbial Communities Farming
System Impacts
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NRI Transitional Treatments asPercent of
Conventional Three Years
It begins with the soil.
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What Drives Microbial Communities? Seasonal and
Year Effects
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LS Means (log MPN/g soil)
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3
2
0
200
400
600
800
1000
1200
1400
1600
1800
Julian Date
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Cropping history of the sampled soils with CT, NT
and SC at CEFS, North Carolina
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Disease incidence of seed rot and damping-off of
soybean in CT, NT and SC soils
Diseases indices
c
b
a
Different letters indicate values are
significantly different at P lt 0.05 level.
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The populations (CFU/ g dry soil) of Fusarium
spp. in CT, NT and SC soils

• Different letters indicate values are
  significantly different at P lt 0.05 level.
• Based on dilution plating.

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Similarity of Burkholderia community based on the
MPN/g soil and Denaturation Gradient Gel
Electrophoresis sequencing (DGGE) in CT, NT and
SC soils using CCA
Farming System impacted Burkholderia Diversity
(H) Richness (R) Evenness (E)
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Similarity of Fusarium community based on
dilution plating and DGGE in CT, NT and SC soils
using CCA
H Shannon indices R Richness E Evenness
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Ecological Function Damping-off of soybean
impacted by soil physical, chemical and
biological factors
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ADVANCING THE FRONTIER OF SUSTAINABLE AG
A B X
Input based Tactic substitution
Process based Tactic diversification