Ergot in Wheat: A Brief Summary

Wheat infected with Ergot.

Wheat infected with Ergot.

Introduction

We have seen a lot of ergot in the panhandle of Nebraska this year and we have been getting a lot of questions about it.  I wanted to write a some-what brief article about what ergot is, why it is important, and what can be done to manage for it.

Ergot is a plant disease in cereal crops and grasses caused by the fungus Claviceps purpurea.  The disease manifests itself as dark colored sclerotia (ergot bodies), replacing the seed or kernel of the infected plant.  The sclerotia are often black or dark purple with a white interior, vary in size, and are sometimes similar in shape to the infected plant’s kernel or seed.

ergot comparison

Ergot as it appears on a head of wheat and in harvested wheat.

Consumption of infected grain causes a condition called ergotism in animals and humans and can cause a variety of symptoms that range from convulsions to gangrene.  Wheat is considered ergoty when it contains more than 0.05% ergot bodies by weight.  Most sclerotia can be removed by modern cleaning equipment however, if they are the same size as wheat kernels, it is more difficult and costly to clean wheat within acceptable levels using screening.

ergot grading

The images above contain a 500 gram sample of wheat. The one on the left has 0.088% ergot by weight and is illegal by USDA grading standards. The one on the left is the same wheat but has been cleaned with a screener and now has 0.04% ergot which is an acceptable level.

Host Crops and Grasses

Rye and some grasses are more susceptible to ergot infection due to the open pollination process of reproduction that allows easy access of the fungus to reproductive units within the plant.  Crops such as wheat and barley are less susceptible because they are self-pollinated but can be more prone to the disease if weather conditions are cool and wet during flowering.

Life Cycle

Sclerotia fall to the ground in the fall and survive on the surface until the following spring.  The sclerotia germinate and produce tiny mushroom-like bodies about the size of a pin which then burst to shoot spores into the air.  These spores are carried by the wind to grain heads where they infect the plant.

An ergot sclerotia produces tiny mushroom-like bodies from which it produces spores.

When an ergot sclerotia germinates it produces tiny mushroom-like bodies from which it releases spores.

When the ergot spores infect the plant they infect the flower and cause it to produce an ergot body (sclerotia) instead of a seed or wheat kernel.  About 5 days after infection, the floret excretes a sticky sap-like substance called “honey dew”.  This substance contains spores that can be spread to other florets by rain splash and insects.  The floret can excrete spores for as long as flowering occurs.

Infection by ergot can occur when sclerotia germinate or when a flower is infected.

Infection by ergot can occur when sclerotia germinate or when a flower is infected.

Conditions

Ideal conditions required for sclerotia germination are a cold winter followed by wet soils in the spring.  Wet, cloudy and cool weather conditions during the period of flowering increase the window of infection for spores to enter florets.  Wet and cool weather conditions may also favor higher insect populations which help spread the spores.  Ergot has also been linked to copper deficiency in the soil which often occurs in sandy soils.

Control

Many factors have to occur in order for there to be widespread occurrences of ergot.  Unfortunately there is not much that can be done to control ergot in the field.  There has been limited to no success in spraying fungicide during flowering in order to prevent spore infection.  There has also been limited success in spraying fungicide in the spring in order to prevent sclerotia germination.  Prevention before an ergot infection occurs is the best management policy.

Management Strategies Include:

  • Scout the field and harvest in parcels.  Ergot infection can be greater near the edges of the field due to infection from roadside grasses or neighboring fields.
  • Rotate cereal crops with non-susceptible crops for one year or longer. Sclerotia usually cannot survive in the soil for more than 1 year.
  • Deep plow fields to bury crop residue.  Sclerotia will not germinate if buried in 1″ or more of soil.  Sclerotia can over winter if they fall onto the ground so if you have ergot one year there is a good chance that there will be some the next year.
  • Plant clean seed that is ergot free in order to avoid reintroducing fungus into the field.
  • Eliminate wild grasses and rye that are susceptible to ergot infection before they flower.  This will reduce the amount of carriers and thus reduce the chance of crop infection.

If you want to read more about ergot here are a couple links to other articles.

http://www.agriculture.gov.sk.ca/ergot-of-cereal-grasses

Ergot

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One thought on “Ergot in Wheat: A Brief Summary

  1. Pingback: Tucker Talk: February 19, 2016 | farmer scoop

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