Symptoms of Gibberella Stalk Rot

Gibberella stalk rot

• Rotting at roots, crown and lower internodes are symptoms of Gibberella stalk rot
• Perithecia (small black fungal fruiting structures), may develop on the stalk surface near the node (can be scraped off with fingernail)
• Pink to reddish coloration of pith and vascular strands (bundles)
• Pith of the inner stalk may deteriorate leaving only the vascular bundles intact
• Destruction of the nodal plate
• Later stages - plant turns gray-green, internodes turn straw colored or dark brown and are easily pinched between fingers
• Late-season snapping of stalks at the node

Gibberella vs. Fusarium

Fusarium stalk rot

• Gibberella may look similar to Fusarium stalk rot
• Closely related fungi cause these diseases
• Distinguish by inner stalk color
  • Gibberella - red/pink
  • Fusarium - white/pink/salmon

Facts

• Caused by the fungus Gibberella zeae
• Occurs wherever corn is grown throughout the world
• Infects other cereals like wheat, barley, oats and rye
• Overwinters in infected crop residue of corn or other cereals
• Ascospores produced in perithecia are disseminated to corn plants by wind and rain splash
• Insect injury often allows pathogen to enter the plant
• Can infect corn at the leaf sheaths, brace roots or roots. Infection continues from roots into lower stem
• Secondary cycles of disease are by conidia produced within disease lesions
• Infection often occurs after pollination. Disease can progress rapidly with warm, wet weather during corn reproductive stages
• Environmental and physiological stresses may weaken the plant and allow disease development

Disease Cycle

Impact on Crop

• Greatest damage to corn crop is usually caused by stalk breakage or lodging
  • Lodging slows harvest and usually results in some ears left in field
  • If ears contact ground, grain quality may be reduced
• Stalk deterioration disrupts water and nutrient flow, and plants may die prematurely
  • Affected plants have lightweight ears and poorly filled kernels (low test weight)
• Gibberella zeae may also infect ears

Management of Gibberella Stalk Rot

• Select hybrids with good stalk strength and resistance to leaf diseases
• Rotate crops. Corn following soybeans often has less stalk rot and higher yield than continuous corn
• Use a tillage system that chops and incorporates residue to break it down
• Do not use plant populations higher than recommended for the hybrid
• Soil test and follow fertilizer recommendations; maintain proper nitrogen:potassium balance
• Reduce stresses when possible -- stalk rots are favored by plant stress following pollination
• Control leaf diseases with fungicides if necessary
• Control corn rootworm and corn borer. Pioneer brand hybrids with Herculex® Insect Protection traits are available to help manage these pests
• Scout preharvest to determine stalk condition and schedule harvest based on stalk quality as well as grain moisture