A fungus that thrives under cool and wet conditions has invaded the U.S. wheat crop and is marching north into Canada.”Almost every state that grows wheat has reported a stripe rust problem,” said Xianming Chen, stripe rust specialist with the United States Department of Agriculture.Infection levels are similar to 2005 when Kansas and Texas lost seven and 17 percent of their wheat crops respectively to the disease. Nationwide losses amounted to 2.45 million tonnes of grain or three percent of the total wheat crop that year.Chen expects the disease will also be a problem in Canada.Bruce Burnett, director of weather and market analysis with the Canadian Wheat Board, is particularly concerned about the impact the disease may have in Montana, North Dakota, Saskatchewan and Manitoba.Wet weather has created ideal conditions for disease propagation and stripe rust can be particularly devastating when it attacks crops that are in the early stages of development.Rust diseases typically show up in Manitoba and eastern Saskatchewan from spores brought up on southerly winds from the U.S.Manitoba Agriculture has issued an information sheet advising growers to scout their winter and spring wheat crops looking for signs of the disease, which is characterized by small, yellow pustules appearing in linear rows along the length of the leaf blade. A Cargill agronomist based in Elm Creek, Man., posted on a USDA cereal rust website that stripe and leaf rust have been observed in southern Manitoba in four different lines of hard red spring wheat: AC Domain, Harvest, Kane and Glenn.Manitoba Agriculture said varieties grown in the province are generally susceptible but the disease can be managed by timely application of one of the numerous fungicides available to control stem rust.The disease causes yield reduction by destroying leaves, which interferes with photosynthesis and grain fill.Burnett said it’s too early to assess how much damage the disease will cause but there is nothing alarming in early harvest results from Texas and Oklahoma. Harvest is just getting underway in Kansas.Chen said the most severe infections are in Texas, Louisiana, Arkansas, Kansas, Oklahoma and Nebraska. Infection rates are up to 100 percent in some fields.A USDA Cereal Rust Bulletin dated June 10 said yield loss due to stripe rust is likely to be significant in Kansas, the top wheat producing state.Chen said even though 2010 is shaping up to be a repeat of 2005, when there was record damage due to stripe rust, he doesn’t believe the disease will be a market mover.”I don’t expect it to influence price very much,” he said.That’s because losses due to the disease should be partially offset by better than expected yields in fields that are free of infection. Like the fungus, wheat tends to grow well under cool and wet conditions.
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