Corn Stalk Rots An overview of stalk rots

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Corn Stalk Rots An overview of stalk rots
other corn diseases

• Your name here
• County Extension Educator - Agronomy
• Martin A. Draper
• Extension Plant Pathologist

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Corn Disease Concerns

• Seedling blights
• Leaf diseases
• Stalk rots
• Ear rots
• Post harvest diseases (grain molds)

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Corn disease concerns

• Seed and seedling blights
• Leaf diseases
• Root and stalk rots
• Ear rots
• Post harvest diseases

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Corn Disease Problems in No-Till

• Seedling blights
• Stalk and ear rots
• Emerging no-till diseases
• Anthracnose
• Gray leaf spot
• and others...

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Seedling Blights
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Seed and seedling blights

• Pythium blight
• Rhizoctonia blight
• Penicillium blight

• Fusarium blight
• Diplodia blight
• Aspergillus blight

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Seed and seedling blights
Symptoms of Diplodia blight look much like
other seedling blights.
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Managing seed seedling blights

• Plant in a good environment
• Rotation
• Seed treatments
• Captan
• Maxim
• Vitavax
• Apron

Mancozeb Maneb Thiram PCNB
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Leaf Diseases
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Leaf diseases

• Eyespot
• Rusts
• Northern corn leaf blight (NCLB)

• Gray leaf spot
• Anthracnose

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Leaf diseases

• Eyespot
• Residue-borne
• Produces small translucent spots
• Resistant hybrids available

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Leaf diseases

• Anthracnose
• Residue-borne
• Spots start small and coalesce, becoming large
  and irregular in shape

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Leaf diseases

• Northern corn leaf blight (NCLB)
• Residue-borne
• Common in SD
• Causes large lesions
• Favored by moderate temperatures and high
  humidity

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Leaf diseases

• Rusts
• Spores blown northward
• Resistant hybrids available
• Usually not severe

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Leaf diseases

• Gray leaf spot
• Residue-borne
• Emerging disease problem in SD
• Resistant hybrids available

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Managing leaf diseases

• Plant resistant hybrids
• Residue management
• Rotation
• Tillage
• Fungicides
• Tilt, Bravo, and Mancozeb are labeled

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Corn disease concerns

• Seed seedling blights
• Stalk and ear rots
• Diplodia stalk rot
• Fusarium stalk rot
• Gibberella stalk rot
• Gibberella zeae / Fusarium graminiarum
• Also causes Fusarium head blight (scab) in wheat

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Corn diseases to watch

• Anthracnose Gray leaf spot
• others also...
• Diseases of minimum tillage
• Compounded by
• Tight rotation or continuous corn
• High rainfall or irrigation

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Corn diseases to watch

• Anthracnose
• Leaf spot and stalk rot

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Corn diseases to watch

• Gray leaf spot
• Leaf spot
• Often severe in eastern corn belt

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Fungicide suppression of Gray leaf spot
GLS severity on ear leaf ()
No significant differences across treatments,
1998, West Lafayette, IN Shaner Buechley, FN
Tests 53142
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Stalk and Ear Rots
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Stalk rots

• Traditionally the most economically
• important diseases of corn
• Not immediately obvious disease symptoms
• Usually develop on lower 1-2 internodes
• May not be an issue unless there is wind before
  harvest

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Corn Disease Concerns

• Stalk and ear rots
• Diplodia stalk rot
• Fusarium stalk rot
• Gibberella stalk rot
• Gibberella zeae / Fusarium graminiarum
• Also causes Fusarium head blight (scab)
• in wheat

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Stalk rots

• Anthracnose
• Fusarium stalk rot
• Gibberella stalk rot

• Pythium stalk rot
• Diplodia stalk rot

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Stalk rots

• Anthracnose stalk rot often begins as a leaf
  blight that spreads into the stalk
• Favored by
• Wet weather or irrigation
• Heavy residue
• Continuous corn

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Stalk rots

• Pythium stalk rot begins as a leaf blight that
  spreads into the stalk
• Appears soon after tasseling

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Stalk rots

• Pythium stalk rot
• Causes a soft, wet rot
• Less common in SD
• Favored by
• Cool, wet soils
• Heavy residue

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Stalk rots

• Fusarium stalk rot
• Caused by F. moniliforme
• Infects from residue, through roots

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Stalk rots

• Fusarium stalk rot
• Light pink color in pith
• Favored by
• Heavy residue
• Continuous corn
• Wet weather or irrigation

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Stalk rots

• Charcoal rot
• Early maturity
• Black specks (microsclerotia) in pith
• Favored by
• Continuous corn
• Wet weather early season
• Drought stress late in year

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Stalk rots

• Gibberella stalk rot infects through roots from
  infected residue in soil
• Also causes head blight in wheat (scab)

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Stalk rots

• Gibberella stalk rot favored by
• Heavy residue
• Continuous corn

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Managing stalk rots

• Reduce plant populations
• Manage fertility (avoid high N low K)
• Rotation
• Residue management
• Choose hybrids with good stalk strength and
  lodging resistance ( resistant hybrids)

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Ear rots

• Diplodia
• Penicillium

• Fusarium moniliforme
• Gibberella zeae

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Ear rots

• Need to be aware of mycotoxin risk
• Store below 14 moisture, to minimize hazard

Penicillium ear rot
Aspergillus ear rot
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Ear rots

• Diplodia (A), G. zeae (B), and F. moniliforme (C)
  ear rots
• Need to be aware of mycotoxin risk
• Store below 14 moisture

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Post harvest diseases

• Penicillium, and Aspergillus seed rots (L-R)
• Need to be aware of mycotoxin risk
• Store below 14 moisture

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Rotation Disease Management

• Critical factor in No-Till
• Important in managing most diseases
• NOT a new concept!!