Management critical to preventing ergot outbreak

Crop rotation, mowing field edges, and good agronomic practices can reduce impact of ergot infestation

When it comes to controlling ergot, the best control is prevention.

Ergot fungi, which produce mycotoxins that are extremely toxic to humans and livestock, affects all cereal crops except oats.

“Although not significantly impacting yield, the low tolerance level for affected grain can cause grain rejection or downgrading at the elevator,” said provincial crop specialist Neil Whatley. “Forage grasses and roadside grasses are also susceptible to this fungal disease. Since no seed treatments, pesticides or resistant varieties are available as control measures, prevention is the only way to manage this disease.”

Ergot appears as dark, hardened resting bodies (sclerotia) in harvested grain that either fall to the ground or become harvested with the grain. Prolonged wet soils in spring and early summer promote germination of disease spores from over-wintering sclerotia in the soil. During the early part of the growing season, the disease cycle has two stages.

Primary infection occurs when wind blows spores from germinating sclerotia to the tiny florets of flowering cereal crops or field edge grasses. The ergot fungus then produces another spore type in infected florets that results in a mass of spores and a sugary, sticky substance. Secondary infection happens when these spores stick to insects or are splashed by rain drops and spread to florets of nearby cereal or grass heads.

“The most effective preventive measures are crop rotation and mowing field edges,” said Whatley. “Since ergot bodies only remain viable for one to two years in the soil, rotation out of cereals for two years limits infection (and) especially do not plant a cereal crop on rye or triticale stubble. Since they can be a major infection source, field edge grasses should be mowed prior to their flowering period and nearby forage grasses should be cut or grazed before they flower in the heading stage.”

A uniform crop stand limits the flowering period (when plants are susceptible to ergot infection), so good seeding practices are recommended. That includes:

  • using seed with high germination rates and using a higher rate to prevent tillering
  • seeding shallow and at an even depth into soil that isn’t too cold
  • maintaining a balanced fertilizer program
  • preventing herbicide injury to the crop including avoidance of late herbicide applications

Deficiencies in copper and boron can lead to reduced pollen viability which may also extend the flowering period. Wheat and barley are normally closed flower self-pollinators. However, a reduction in pollen viability causes these normally closed flowers to open to access pollen from adjacent plants, heightening the possibility of infection. Therefore, amendments of copper and boron may help, but only if soil tests indicate a deficiency in these micronutrients.

“If a field does end up having a significant amount of ergot in cereal heads at harvest time, delaying swathing/harvesting can allow the wind to blow ergot bodies from infected crop heads prior to harvesting,” said Whatley. “If the headlands are more infected from field edge grasses, harvest and bin grain from the headlands separately.”

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