Fusarium Head Blight (Scab)

Pathogen Facts

  • Several species of fusarium are capable of causing disease, but fusarium head blight (FHB) is caused by the fungus Fusarium graminearum (Gibberella zeae), which also causes Gibberella stalk and ear rot in corn.
  • This pathogen overwinters on the soil and stubble of susceptible host crops (like corn and wheat).
  • Infected grain has reduced quality due to the DON vomitoxin (deoxynivalenol) produced by this pathogen.
    • Grains contaminated with mycotoxins are a threat to humans and livestock that consume them.

Photo - Wheat head showing bleaching symptoms after infection from Fusarium graminearum.

Wheat head showing bleaching symptoms after infection from Fusarium graminearum.

Conditions Favoring Disease

  • Disease either overwinters in infected seed or on crop debris.
  • Spores are carried to wheat via wind during initial infection.
  • Infection occurs during the flowering stage. The anthers and pollen serve as a food source for the germinating fungus.
  • This disease is more severe in no-till fields, particularly in wheat following corn due to larger amounts of primary inoculum.

Photo - Variation in wheat head infection by Fusarium graminearum.

Variation in wheat head infection by Fusarium graminearum. Photo courtesy of Matt Montgomery, Field Agronomist.

Symptoms

  • Wheat heads will bleach prematurely, either partially or fully.
  • Warm weather can stimulate the development of light pink sporodochia on the rachis and glumes of spikelets.
    • Later in the season, blueish-black spherical fruiting bodies will form.
  • Grain will shrink and wrinkle, becoming shriveled and varying in color from pink to brown to soft gray.
    • Reduced grain size also results in a lower test weight.
  • When temperatures range from 77-86 °F, symptoms will show three days after infection.

Photo - Wheat head infected with Fusarium graminearum.

Wheat head infected with Fusarium graminearum. Both pink colored spores and darker fruiting bodies are visible.

Management Considerations

  • Fusarium graminearum overwinters in crop debris so production practices that reduce the amount of crop residue on the surface, such as tillage and crop rotation, will decrease the amount of primary inoculum.
  • Selecting tolerant cultivars and varieties can lessen the severity of infection.
  • Some combines can be adjusted to flush out lightweight  infected grain, reducing seedborne spread of the disease.
  • During the flowering period, foliar fungicides can be applied to mitigate the impacts of fusarium head blight.
    • Farmers must consider the cost of the application and market value of their grain before determining if fungicides will be an economical solution.

References



Author: Madeline Henrickson
May 2020

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary..