Nutrient Interactions with Plant Diseases

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Nutrient Interactions with Plant Diseases

• Kent L. Martin
• Southwest Research Extension Center
• Kansas State University

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Overview

• Background
• Discuss each nutrient
• Role of the nutrient in plants
• Relation or interactions with plant disease

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Background

• 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 Uptake Form
Nitrogen, N NH3, NO3-
Phosphorus, P HPO4-2, H2PO4-
Potassium, K K
Ca, Mg, Zn, Mn, Cu, Fe, Ni XX-2
Sulfur, S SO4-2
Chlorine, Cl Cl-
Boron, B H3BO3
Molybdenum, MO MoO4-2
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Nitrogen

• Applied in highest quantity in crop production
• Most N in soil is not available
• Most extensively affects plant disease
• May increase or decrease or depend on form of N

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Plant Diseases Affected by N
Disease Host N NH4 NO3
Root Rot Canola D - -
Aflatoxin Corn D D -
Grey Leaf Spot Corn I - -
Leaf Spot Cotton - D -
Root Rot Cotton D - -
Stem Canker Soybean D - -
Stem Rot Sunflower D - -
Eyespot Wheat - I D
Mildew Wheat I - -
Take-all Wheat D D I
Tan Spot Wheat D D -
Seed Infection Cereals I - -
Adapted from Huber and Thompson
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Rate, Timing, and Form of N Applicaiton
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Reducing Disease With N

• Maintain a balanced fertilizer program
• 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

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Phosphorus

• Taken up by plants as HPO42- or H2PO4-
• Important for energy transfer in plants
• Cell division and proper growth
• Increases tiller number, head number and yield
• Creates a stay-green effect in plants
• Relationships with disease is inconsistent
• Balanced soil fertility is important
• Reduce plant stress, improves resistance and
  decreases disease risk

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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
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Why P Affects Disease

• 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

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P Management for Disease Control

• Rate
• Source
• Water soluble
• Method of Application
• Low soil P band high P band or broadcast
• Soil pH
• Moisture
• Foliar spray has decreased some foliar pathogens
  such as powdery mildews

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Potassium

• 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

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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
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K Management for Disease Control

• Rate
• Application Timing
• Preplant
• Method of Application
• Band if low testing Broadcast if medium or low
• Moisture supply
• Allow for uptake
• Appropriate pH

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Calcium

• Highly weathered soils lt 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

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Magnesium

• 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

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Mg and Disease Interactions
Effect of Mg on Wheat Diseases
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

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Sulfur

• 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

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S and Disease Interactions

• Increased S decreases the following in wheat
• Powdery mildew
• Sharp eyespot (44 in some studies)
• Stem rust
• 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

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Iron

• 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

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Manganese

• Exists in plants as Mn2
• Central element in photosynthesis
• Mn decreases the following in wheat
• Mildew
• Rust
• Take-all

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Manganese

• In general
• Fungal and bacterial diseases decrease with Mn
• Viral diseases increase with increasing Mn
• Direct application may not ward off disease, but
  inadequate levels may increase incidence of
  disease

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Zinc

• Very important for cell division
• Important for water and other nutrient uptake
• Commonly deficient in corn
• Deficient in low organic matter high pH soils
• Restricted oxygen (water logged) increases
  deficiency
• Can bind with P in roots and limit uptake
• P induced deficiency
• Banding is most effective unless you want to
  increase soil test level

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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
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Copper

• Component of three forms of proteins
• Important in cell wall and lodging reduction
• Deficiency occurs in high organic matter, highly
  weathered soil
• Cu increases
• Leaf rust
• Cu decreases
• Ergot, Stripe rust, Take-all, Smut

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Copper

• Acts as a direct toxic element
• Some of the first fungicide and bactericides
• Regulates enzymes that defend the plant against
  disease infection

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Chlorine

• 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
• Inhibits nitrification, manganese increase,
  regulate osmosis, host resistance, biological
  control, direct toxic effects, reduces drought
  stress

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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
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Molybdenum

• Essential in small amounts
• Used in nitrogen reduction
• Enhances sprouting resistance
• Effect on plant diseases
• Deactivates viruses
• Direct toxicity
• Inhibition of nematodes
• Often considered to have no direct effect on
  disease, but is in question

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Boron

• 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
• Decreases rust in wheat
• Do not apply in a band

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Nickel

• 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
• Especially in rust fungi

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Silicon

• Very abundant in the earth crust (28)
• Most plants have adapted to take up sufficient Si
• Most research conducted with rice
• 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

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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
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Aluminum

• Although essential, it is commonly toxic to
  plants due to quantity (low pH)
• 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

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Summary

• 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