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Cool weather brings threat of sorghum ergotKansas Honeydew could begin dripping from grain sorghum and forage sorghum heads in Kansas this year, according to a Kansas State University scientist. The cause: sorghum ergot. This disease occasionally causes problems in very late-maturing grain sorghum and on male-sterile forage sorghum in the Central Plains, said K-State Research and Extension plant pathologist Doug Jardine. Why the concern this year? "The combination of cool nighttime temperatures and late-flowering sorghum in late August and early September is the reason," Jardine said. "Cool nighttime temperatures inhibit pollination and create an avenue of infection for the organism." Sorghum ergot infects the ovaries of sorghum flowers and often converts them into a white, fungal mass. The most obvious external symptom of infection is the sticky honeydew that often drips onto the leaves and soil, he said. "Sorghum ergot infects only unfertilized ovaries. Once fertilized, an ovary becomes resistant to infection. Any condition that prevents or delays fertilization increases the risk of ergot," he added. Sorghum plants with inherent male sterility or with pollination difficulties caused by cool temperatures are most severely affected by ergot. Once an infection has occurred, there is nothing producers can do to cure the disease, Jardine said. The only thing producers can do at that point is devise a management plan for trying to avoid the problem next season. "To minimize the development of ergot and limit its impact, producers should try to avoid late planting next year," he said. The goal is to avoid low evening temperatures (below 55 degrees F) during the period three to four weeks prior to flowering and from flowering to five days thereafter. Fields that bloom in July and August seldom, if ever, have problems with ergot, the plant pathologist said. Photos of sorghum ergot are available in the publication, "Diagnosing Sorghum Production Problems" S-125 at: http://www.oznet.ksu.edu/library/crpsl2/sections/s125_C.pdfor at county and district K-State Research and Extension offices. ===Sidebar:==== Sorghum ergot can affect quality and utilization Sorghum ergot can lower grain and seed quality, makes threshing difficult, reduces germination and seedling emergence, and predisposes seedlings to other disease, said Kansas State University scientist Doug Jardine. It also reduces grain yield because infected flowers do not produce grain. The honeydew can coat the surfaces of harvest and handling equipment, making them unusable, or causing mechanical damage in the worst case scenarios, said Jardine, who is a plant pathologist with K-State Research and Extension. As examples, he cited reports of auger motors burning up from trying to push infected grain through. "Infected grain left in a truck or grain cart overnight can often end up looking like a Rice Krispie treat," he said. Evidence to date suggests that sorghum grain contaminated with sorghum ergot sclerotia has little, if any, implication for animal health, Jardine said. Otherwise, there are a few other possible options for handling and marketing sorghum infected with sorghum ergot. "In the past, growers have been successful in harvesting a field almost immediately after a hard rain that washes away most of the sticky residue. Unfortunately, that residue will reappear again within a few days of the rainfall. Others have tried to swath and bale it. Some producers have turned cattle out to graze it off, and still others have tried to harvest the grain while it is frozen," he said. If the option is available, ethanol plants may take the grain, Jardine added. "Where sorghum ergot occurs, the panicles left in the field after harvest may still have some of the honeydew and fungal spores on them, but it's very unlikely that this infected residue would cause a re-infection problem next fall," he said. 10/20/08 Date: 10/16/08 Advertisement
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