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Ergot in Small Grains
Ergot may be present in durum and hard red spring wheat. What causes ergot and how do we manage it in mature grain fields?
Ergot is usually considered a disease of rye, but it also occurs on wheat, triticale, barley, oats, millet and many grasses. The fungus attacks only the seed-producing organs and usually the yield losses caused by the disease are less serious than the losses from discounted grain quality. The ergot bodies that replace the kernels are toxic to humans and animals and they are difficult to remove from harvested grain without special equipment.
Ergot infections first appear during flowering as yellowish droplets of sticky exudate on the infected florets (the honeydew stage). As plants mature, some of the kernels are replaced by purplish black sclerotia that protrude from the spikelets. The dark ergot sclerotia can be detected in the threshed grain as well.
The fungus over-winters on the soil surface or as sclerotia in plant debris. In the spring and early summer, small stalk-like stromata grow out of the sclerotia. Ascospores are released that may infect the stigmas and ovaries (parts of the flower) of small grains and grasses. Within a few days, honeydew that contains conidia is exuded from infected ovaries. The honeydew is disseminated among the flower by insects. As the flowering stage passes, the production of honeydew ceases and infected ovaries form fungal sclerotia instead of grain. By the time the plant has matured, the sclerotia have developed into conspicuous dark, hornlike structures, two or three times as large as normal kernels.
Ergot is more prevalent in cool, temperate climates. The prevalence of the disease may be related to the susceptibility of native grasses in these areas. The level of ergot among varieties usually depends more on flowering habits and floral structures than on genetic resistance to the fungus. Crops in which the florets remain open for extended periods during the flowering stage are more likely to become infected. Ergot levels may be reduced by cutting grasses along roadways and borders of the fields before heading.
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MANAGEMENT TIPS FOR HARVESTING ERGOT INFESTED GRAIN
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1) Survey grain field edges that border grassy areas (roadsides, rock piles, etc.) since ergot over-winters in grassy areas.
2) If ergot is present and confined to field borders, thresh those areas separately.
3) Store ergoty grain separately from non-infested grain. Flour millers do not want any ergot. In the commercial grain trade, wheat or durum is graded as "ergoty" when it contains more than 0.05 percent by weight of the ergot sclerotia. Rye is graded "ergoty" when it contains more than 0.3 percent by weight of ergot sclerotia. Triticale, oat, or barley are "ergoty" when they contain more than 0.1 percent ergot.
4) Attempt to clean separately stored ergoty grain before marketing or contact elevator after harvest for cleaning arrangements.
5) Do not contaminate "clean grain."
For more information see http://www.ext.nodak.edu/extpubs/plantsci/crops/pp551w.htm
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