| Abstract/Contents: | "The battle against Fusarium blight, a fungal disease that plagues countless golf courses and turf areas in much of the United States and southern Canada, can be waged more effectively as a result of a discovery attributed to Cornell University scientist Richard W. Smiley. In fact, Fusarium, the fungus which had been blamed for the blight, is not the culprit at all, according to Smiley. Through laboratory work and greenhouse field tests conducted over the past four years, the Cornell scientist successfully tracked down two fungal species that are capable, he says, of causing the blight independently. A specialist in turfgrass disease, Smiley says that the real culprits are Leptosphaeria korrae that has recently been found to cause "spring dead spot" in Bermuda grass in Australia and Phialophora graminicola, a species regarded up to now as innocuous. Fusarium blight afflicts lawns mainly during the periods of high temperatures in July and August, causing large patches of grasses to die. One of the most widespread lawn diseases known, Fusarium blight has plagued 35 states in the nation and southern Canada for more than three decades, according to Smiley. Kentucky bluegrass, used widely in turf areas, is more vulnerable. "We have demonstrated that Fusarium blight is initiated by several fungal species other than Fusarium," Smiley says. "Further infection of the grass by Fusarium may or may not be important, depending upon the environmental conditions in the lawn." Although two of the culprits have been isolated and identified in the Cornell laboratory, Smiley suspects that a few other closely related species that are yet to be found and identified may cause similar ailments. Now that the cause of these diseases had been determined, scientists are able to map out new control strategies to combat the maladies. In greenhouse and field experiments, Smiley found that some of the Kentucky bluegrass varieties, such as Adelphi, Enmundi Sydsport and Touchdown, are more tolerant to the diseases than others. Even more resistant than these are other types of popular turfgrasses such as perennial ryegrasses and tall fescues. "Control of these diseases can be achieved most economically by mixing the disease-tolerant grasses into the turf stand," Smiley points out. Lawn care that will reduce summer stresses on the grass also plays an important role in combating the problem. Among steps being recommended by Smiley are adequate watering and fertilization before the disease attacks the lawn in summer. In addition, the lawn should not be mowed too low. As for chemical controls, Smiley also found that each of the fungal species responsible for the disease is controllable with fungicides containing benomyl (such as Tersan 1991), methyl thiophanate (Fungo), ethyl thiophanate (CL 3336), propiconazole (Banner), or fenarimol (Rubigan). As far as Fusarium blight is concerned, the Fusarium fungus had been proven to be a relatively innocent bystander. Yet this fungus remains one of the most pervasive disease-causing organisms known, as it causes other turf diseases. In this sense, the Fusarium fungus is still an extremely important pathogen of plants." |
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