Transcript Nutrient Interactions with Plant Diseases

Nutrient Interactions
with Plant Diseases
Kent L. Martin
Southwest Research Extension Center
Kansas State University
Overview
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Background
Discuss each nutrient
Role of the nutrient in plants
Relation or interactions with plant disease
Background
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Many interactions of plant nutrients and plant
responses to stimuli
Maintaining appropriate nutrient levels allows
for proper growth and development
16-17 essential plant nutrients
C, H, O
 N, P, K
 Ca, Mg, S
 Fe, Mn, Zn, Cu, B, Mo, Cl, Co, Ni?
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Background
Nutrient
Nitrogen, N
Phosphorus, P
Potassium, K
Ca, Mg, Zn, Mn, Cu, Fe, Ni
Sulfur, S
Chlorine, Cl
Boron, B
Molybdenum, MO
Uptake Form
NH3+, NO3HPO4-2, H2PO4K+
XX-2
SO4-2
ClH3BO3
MoO4-2
Nitrogen
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Applied in highest quantity in crop production
Most N in soil is not available
Most extensively affects plant disease
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May increase or decrease or depend on form of N
Plant Diseases Affected by N
Disease
Host
N
NH4
NO3
Root Rot
Canola
D
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Aflatoxin
Corn
D
D
-
Grey Leaf Spot
Corn
I
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-
Leaf Spot
Cotton
-
D
-
Root Rot
Cotton
D
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-
Stem Canker
Soybean
D
-
-
Stem Rot
Sunflower
D
-
-
Eyespot
Wheat
-
I
D
Mildew
Wheat
I
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-
Take-all
Wheat
D
D
I
Tan Spot
Wheat
D
D
-
Seed Infection
Cereals
I
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Adapted from Huber and Thompson
Rate, Timing, and Form of N
Applicaiton
Reducing Disease With N
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Maintain a balanced fertilizer program
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Prevent tissue cannibalization with enough N
Make timely applications of N to avoid
excessive N or high N loss
Use different forms of N to enhance control
Phosphorus
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Taken up by plants as HPO42- or H2PO4Important for energy transfer in plants
 Cell division and proper growth
 Increases tiller number, head number and yield
 Creates a stay-green effect in plants
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Relationships with disease is inconsistent
Balanced soil fertility is important
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Reduce plant stress, improves resistance and
decreases disease risk
P and Disease Interaction
Effect of P on Wheat Diseases
Disease
Effect of P
Smut
D
Powdery Mildew
I or D
Bunt
I or D
Take-all
D
Scab
I
Root Rot
I or D
Blotch
I
Why P Affects Disease
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Increase in plant maturity that attacks young
plant tissue
Increased plant vigor with adequate P
Highly specialized pathogens may attack
vigorous plants, while less specialized pathogens
attack weak plants
Increases plant defense mechanisms
P Management for Disease
Control
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Rate
Source
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Method of Application
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Water soluble
Low soil P – band; high P – band or broadcast
Soil pH
Moisture
Foliar spray has decreased some foliar pathogens
such as powdery mildews
Potassium
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Taken up in very large quantities
Mobile in the plant
Increases root growth
Improves uptake of water and nutrients
Reduces lodging
Regulates enzymes involved in plant growth
K and Disease Interaction
Effect of K on Wheat Diseases
Disease
Effect of K
Leaf blotch
D
Root Rot
I
Take-all
I or D
Stem Rust
D
Leaf Rust
D
Stripe Rust
D
Bunt
I or D
Smut
I
Powdery Mildew
D
K Management for Disease
Control
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Rate
Application Timing
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Method of Application
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Band if low testing; Broadcast if medium or low
Moisture supply
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Preplant
Allow for uptake
Appropriate pH
Calcium
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Highly weathered soils < 1% Ca
Calcareous soils as much as 50%
Exchangeable Ca and soil solution Ca can reach
plants
Ca stimulates root hair growth and normal leaf
development
Wheat root rot is decreased by Ca application
Most recognized in vegetable crops
Important in post harvest fruit and tuber disease
Magnesium
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Component of structural tissues
Used for rapid growth and cell division
Synthesizes sugars, oils, and fats
Fruit development
Essential for proper microbial growth in soil
Mg and Disease Interactions
Effect of Mg on Wheat Diseases
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Disease
Effect of Mg
Smut
I
Take-all
I or D
Take-all decreased with MgCl2 and increased
with MgCO3
The balance of Mg in relation to N and K can
also influence disease resistance/susceptibility
Sulfur
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Mobile in soil, immobile in plants
Significant amounts come from organic matter
Affect disease directly as biocides and indirectly
by enhancing plant resistance and availability or
other nutrients
Sulfur induced resistance enhances plants
natural resistance mechanisms
S and Disease Interactions
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Increased S decreases the following in wheat
Powdery mildew
 Sharp eyespot (44% in some studies)
 Stem rust
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Elemental S may enter fungal cell wall and
disrupt reactions in metabolism of the pathogen
May also be direct toxic effects to pathogens
Initially found as foliar reactions, later as
increased S levels in soil
Iron
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Essential for proteins, electron transfer, and
redox reactions
Immobile in soil and plants
Affected by crop and genetics or varieties
Iron is nearly always ‘bound’ in some form
Most soluble iron is present as iron siderophores
The siderophores are important as agents of
protection from bacteria
Manganese
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Exists in plants as Mn2+
Central element in photosynthesis
Mn decreases the following in wheat:
Mildew
 Rust
 Take-all
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Manganese
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In general:
Fungal and bacterial diseases decrease with Mn
 Viral diseases increase with increasing Mn
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Direct application may not ward off disease, but
inadequate levels may increase incidence of
disease
Zinc
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Very important for cell division
Important for water and other nutrient uptake
Commonly deficient in corn
Deficient in low organic matter high pH soils
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Can bind with P in roots and limit uptake
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Restricted oxygen (water logged) increases deficiency
P induced deficiency
Banding is most effective unless you want to
increase soil test level
Zn and Disease Interactions
Effect of Zn on Wheat Diseases
Disease
Effect of Zn
Root Rot
D
Take-all
D
Mildew
I
Crown Rot
D
Copper
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Component of three forms of proteins
Important in cell wall and lodging reduction
Deficiency occurs in high organic matter, highly
weathered soil
Cu increases:
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Leaf rust
Cu decreases
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Ergot, Stripe rust, Take-all, Smut
Copper
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Acts as a direct toxic element
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Some of the first fungicide and bactericides
Regulates enzymes that defend the plant against
disease infection
Chlorine
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Required for photosynthesis
Older data showed plant diseases were
suppressed by K, but it was only KCl that
produced the effects
Yield benefits occur where considerable stress or
disease is present
Mechanisms of disease suppression
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Inhibits nitrification, manganese increase, regulate
osmosis, host resistance, biological control, direct
toxic effects, reduces drought stress
Cl and Disease Interactions
Effect of Cl on Wheat Diseases
Disease
Effect of Cl
Root Rot
D
Take-all
D
Mildew
D
Stripe rust
D
Leaf rust
D
Molybdenum
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Essential in small amounts
Used in nitrogen reduction
Enhances sprouting resistance
Effect on plant diseases
Deactivates viruses
 Direct toxicity
 Inhibition of nematodes
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Often considered to have no direct effect on
disease, but is in question
Boron
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Structural component of cell walls
Affects carbohydrate transport
B disease interactions
Direct toxicity
 Restricts fungal hyphae from movement through the
cell walls
 Synthesizes lignin as a pathogen barrier
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Decreases rust in wheat
Do not apply in a band
Nickel
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Most recently defined as essential
Only theoretical for considerable time
Typically corrected as foliar spray
Related to nitrogen metabolism in plants
Noted as having fungicidal activity
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Especially in rust fungi
Silicon
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Very abundant in the earth crust (28%)
Most plants have adapted to take up sufficient Si
Most research conducted with rice
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Control of rice blast with various sources and rates
Can create a physical barrier in the cuticle of
plant leaves and sheaths
In many dicots (garden plants), there is a
negative relationship with Si and disease
Si Disease Interaction
Effect of Si on Wheat Diseases
Disease
Effect of Si
Foot Rot
D
Leaf blotch
D
Mildew
D
Rust
Unknown
Eyespot
D
Aluminum
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Although essential, it is commonly toxic to
plants due to quantity (low pH)
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Free aluminum most dangerous
In our environment, it can appear as a P or N
deficiency
Rarely a concern for deficiency and difficult to
study in reference to plant disease
Effects are confused by relation with pH and
other nutrients
Summary
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Maintaining appropriate levels of nutrients will
maintain productivity and inhibit disease
Many interactions occur that have resulted in the
nutrient recommendations we currently use
True and concerning effects of nutrients on
plant disease are few and far between
Great way to illustrate importance of current
recommendations