Karnal Bunt update for December 1997 December 4, 1997 The Karnal bunt issue is at a low ebb but certainly has not gone away. All quarantine regulations remain in place. The 1997 national survey by APHIS should be complete by now, but I have not heard any official word. The only confirmed new identification of Karnal bunt based on a bunted wheat kernel is in San Saba county in central Texas. This is quite a long way from southern Arizona. Checking some agricultural census data, I found that in 1992 San Saba county had about 16,000 acres of wheat and over 600,000 acres of range land. APHIS announced an interim rule November 24 to regulate this area. The comments period continues until December 24. I am in the process of assaying more than 200 ryegrass samples collected from wheat fields in Georgia and neighboring states. So far I have found KB-like teliospores from 11 samples scattered throughout the state and one from Tennessee. The actual spore numbers are very low and I have found only one bunted ryegrass flower. One "hot" spot I have found is in Jasper county, south of Madison. There are only a few wheat fields in this area, but two had teliospores on regress seed. Wheat samples collected by APHIS in 1996 and 1997 had teliospores also, one of them with a very high spore count. The fields I collected from in Jasper county had a lot of ryegrass. We will sample more intensively next spring in the locations where we found teliospores. My preliminary conclusions from the information we have so far is that the ryegrass smut occurs widely but at a very low level. This makes sense because this fungus had not been found before, even from ryegrass seed production fields in Oregon where the spores were found last year. Is the ryegrass smut the same as Karnal bunt? This is still being debated. The ryegrass smut caused Karnal bunt symptoms and spores identical to KB in greenhouse inoculations conducted by USDA earlier this year. However, the teliospores on ryegrass look different from KB spores from wheat. Results of molecular DNA studies on KB and the ryegrass smut have not yet given a definitive answer. I have sent some of the spores from my samples to a USDA mycologist for further identification. I will present a seminar titled "The Science and Politics of Karnal Bunt" on January 12 at 12 noon in the Miller Plant Sciences Building in Athens as part of the Department of Plant Pathology seminar series. I will summarize information on Karnal bunt and the political realities that have affected our perception of it. I will also present an update at the Wheat-Soybean Expo on January 27 in Macon. Barry Cunfer
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Georgia Invasive Species Task Force |
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