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Wheat Leaf, Stripe Rust Dangers High This Fall -- Experts

Leaf and strip rust can devastate a wheat crop, but the diseases aren't the most common ones in the world for winter wheat because of normally cool fall and early winter temperatures.

But, this year's been different in much of the Plains. The mercury's hovered at levels higher than normal for this time of the year, and the warmer temperatures are just what rust needs to lay down a footprint in the crop before it enters winter dormancy. That could spell serious trouble in the spring once the crop resumes growth, according to a team of University of Nebraska Extension plant pathologists.

If you think you have leaf or stripe rust -- or tan spot, which thrives in conditions similar to those that promote rust growth -- you are likely better off getting a feel for where those infections are worst and making plans to treat with a fungicide in early spring after dormancy breaks, according to a bulletin from Nebraska plant pathologists Stephen Wegulo, Bob Harveson, Karen DeBoer and Kevin Korus. Putting it down now likely won't do you a lot of good.

"The occurrence of rust in fall-planted wheat can partly be explained by the moisture and extended warm temperatures we have had this fall. These conditions also favor development of leaf spot diseases such as tan spot. The combination of rust, leaf spot diseases, and occasional subfreezing temperatures, which can injure wheat (leaf tip dieback), can result in fields or sections of fields that appear yellow," according to a university report. "Spraying a fungicide to control rust in the fall may not be economically beneficial. Begin scouting wheat fields early in the spring and prepare to apply a fungicide if you find overwintered rust."

The rust spores usually overwinter in fields in the southern Plains where winter temperatures remain warmer than in northern climes. In places like Kansas and Nebraska, rust's winter survival is usually less likely. But thus far this fall, temperatures have stayed warmer than normal. How much rust pressure you potentially face in your fields will depend on the conditions moving through winter.

"Substantial yield loss can result if rust and leaf spot diseases are so severe as to kill the entire aboveground part of the wheat crop. If this happens, the probability that the wheat will not resume growth in the spring is high. However, based on previous experience, it is unlikely that this will happen in the Nebraska Panhandle," according to the Nebraska plant pathologists. "Cold temperatures should slow disease development, allowing the majority of the wheat crop to go into dormancy and regrow in the spring. If we have a normal winter, the rust spores will be killed. If we have a mild winter, some of the rust may overwinter."

When scouting this fall -- something experts say is critical at this point to get a feel for where you may need to treat with a fungicide in the spring -- look for basic plant injury like leaf die tipback, as well as the rust-colored spores on wheat leaves. On a wider level, the damage shows up as patches of yellowing plants.

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