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Corn: Stalk Rots

Author: OMAFRA Staff
Creation Date: 01 March 2002
Last Reviewed: 01 March 2002
Agronomy Guide > Pub 811: Corn > Stalk Rots

Excerpt from Agronomy Guide for Field Crops (Chapter 3)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

  1. Incidence
  2. Impact of Stalk Rot
  3. Scouting for Stalk Rots
  4. Stalk Rot Management Strategies
  5. Anthracnose Stalk Rot
  6. Gibberella, Fusarium and Diplodia Stalk Rots
  7. Pythium Stalk Rot
  8. Updates on Corn: Stalk Rots
  9. Related links...

Incidence

Fungi cause corn stalk rots, and the amount of damage they cause increases when the crop is under stress. Stresses that contribute to an increase in stalk rot infection include wet or dry conditions; cool evening and daytime temperatures; cloudy weather; leaf diseases (such as rust and Stewart's wilt); leaf and ear damage from hail, birds and frost; incomplete pollination; unbalanced fertility; insect damage (e.g., from European corn borer), high plant populations; hybrid susceptibility and poor soil conditions. All of these factors can increase a corn hybrid's susceptibility to stalk rots.

The distribution and prevalence of stalk and ear rot diseases vary from year to year, but the diseases are present in most years even though it may be at low levels. The majority of stalk rot damage in Ontario is caused by three fungi: Anthracnose, Gibberella and Fusarium, however, both Diplodia and Pythium have also been observed in Ontario.

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Impact of Stalk Rot

Although these fungi cause different symptoms, their ultimate effect on the corn plant is the same; they reduce grain fill and stalk integrity and accelerate senescence. Stalk rot fungi affect the nutrient movement of the corn plant in three main ways:

  1. Sugars (photosynthates) that would be produced through photosynthesis or carbohydrates in the root and stalk are diverted to the fungus and not to the ear. These nutrients allow stalk rot fungi to grow and flourish.
  2. There is a reduction in stalk integrity. To meet the nutrient needs of both the developing ear and the stalk rot organisms, the corn plant will begin to cannibalize itself by moving soluble carbohydrates from the root and stalk. Problems arise when the plant is unable to meet the nutrient requirements of the developing ear and thus is forced to move more carbohydrates than usual. The result is a weaker stalk (prone to lodging) and less resistance to stalk rot fungi.
  3. Finally, the infection and colonization process inhibits or blocks many of the pathways that the plant would ordinarily use to move nutrients. Yield losses (generally 10%-20%) arise from poorly filled ears and harvest losses from lodging.

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Scouting for Stalk Rots

Two methods or techniques are used to scout for stalk rots.

The Push Test

  1. Randomly select 20 plants from five different areas of the field for a total of 100 plants.
  2. As the name implies, push the top portion of the plant and note whether the plant lodged or not.

The Pinch or Squeeze Test

  1. Randomly select 100 plants in the field (20 plants from five different locations).
  2. Remove lower leaves and pinch or squeeze the stalk above the brace roots.
  3. Record the number of rotted stalks.

If 10-15% of plants lodged, harvest the crop early. The extra drying charges that may result will be covered by increased harvest efficiencies with less corn left in the field.

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Stalk Rot Management Strategies

Management begins by reducing crop stresses through:

  • planting hybrids that have good resistance or tolerance to leaf diseases and stalk rots
  • managing insects such as European corn borer
  • good weed control
  • appropriate plant populations
  • a balanced N and K fertility program
  • crop rotation
  • tillage, etc.

Fields should be scouted to determine the amount of stalk rots present, and those fields that have 10%-15% of the stalks rotted should be harvested as early as possible. Crop rotation reduces the potential for stalk rots.

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Updates on Corn: Stalk Rots

No updates available at this time.

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Related links...

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