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UNL research helps understand how to manage wheat diseaseNebraska Wheat streak mosaic can cause major losses in western Nebraska's winter wheat crop if it's not managed. Sharpening wheat growers' ability to manage the disease is the aim of ongoing research at the University of Nebraska Panhandle Research and Extension Center. There's also an updated UNL Extension publication to improve growers' understanding of the disease and what they can do to prevent its spread. Wheat streak mosaic is caused by a virus carried from plant to plant by the tiny wheat curl mite. The only way to successfully manage the disease is to prevent the spread of the mites. Wheat streak mosaic cannot be treated once the plant has been infected. A key method of preventing the virus' spread is to deny wheat curl mites a place to spend the summer, according to Dr. Gary Hein, entomologist at the Panhandle Center. Wheat curl mites need to spend the period between wheat crops (July, August and September) living on green plants if they are to carry the virus from a previous crop, build up their numbers, and transmit the virus to the newly emerging crop in the fall. They cannot survive for more than a few days without this "green bridge." Most frequently, the green bridge is volunteer winter wheat that emerges before harvest, as a result of hail storms, according to Hein. Other plants can also serve as summer hosts for mites, but volunteer wheat is considered the most important green bridge. For several years, Hein has been encouraging wheat growers to control volunteer wheat, either by mechanical or chemical means, as a way of destroying the green bridge and breaking the wheat curl mite life cycle. Hein and graduate student Abby Stilwell continue to look for new information about the spread of wheat streak mosaic. Under Hein's supervision, Stilwell has been conducting research into wheat curl mite movement. Stilwell and Hein presented some of the results at High Plains Ag Lab field days in June and August near Sidney. The question of how far mites can move is difficult to answer, but research is starting to provide some answers, Hein said. Small areas of volunteer wheat are planted in fallow fields, the mite population allowed to build up, and surrounding fields planted to wheat in the fall. The researchers tracked wheat curl mite movement by field surveys, and tracked the spread of wheat streak mosaic by remote sensing. Over the last three years, they observed significant variations in the movement and spread of the wheat streak mosaic virus. Like smoke from a fire, mites move with the wind. They usually spread southeasterly from a source, following the direction of predominant winds in the fall. But what affects the variation in mite spread from one year to another? Stilwell said the data so far suggests three factors: --The area of the original source of mites. The larger the area, the further the mite spread. --The density of mites at the mite source plot. The higher the density, the more the mites will spread. --Fall temperatures. The warmer the fall, the longer the time for mites to spread to and build up in surrounding fields. Eventually, Stilwell said, the UNL researchers hope to develop a model to predict how far the wheat curl mite population will spread in the fall. Hein and Stilwell hope the research will sharpen wheat producers' ability to manage the potentially costly plant disease. Another tool already available to the public is an Extension publication, "Managing Wheat Streak Mosaic," that has been updated and reissued this year. This circular, EC1871, is available on-line at www.ianrpubs.unl.edu. The publication can be found by using the search function and typing in the words wheat streak mosaic. The publication contains information about risk factors, symptoms, mite life cycle and management of wheat streak mosaic virus and its vector, the wheat curl mite, in winter wheat. The Panhandle Research and Extension Center is on the World Wide Web at www.panhandle.unl.edu. ====Photo captions:==== WC1.jpg and WC2.jpg: Microscopic views of wheat curl mites, which carry the virus for wheat streak mosaic. Wheat_curlmite_demonstration.jpg: Graduate Student Abby Stilwell demonstrates how wheat curl mites can spread from a stand of volunteer wheat like smoke dispersing with the wind. Wheat curl mites will survive during the summer on volunteer wheat in hailed out fields, then spread to newly planted winter wheat fields in the fall. They carry the virus for wheat streak mosaic, a disease that can cause serious damage and economic loss. 9/15/08 Date: 9/9/08 Advertisement
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