In part of last week's column I touched briefly on the foliar disease problem (leaf rust) in wheat we encountered last year. We will pick up from last week and discuss in more detail the fungicide products available, application timing and efficacy of foliar fungicides on wheat.

There are two basic types of foliar fungicides for wheat on the market: triazoles and strobilurins. Triazoles are referred to as preventative fungicide, the common trade names for these products are Bumper, Proline, PropiMax, and Tilt. The strobilurins are known are curative fungicides, (Headline, Quadris).

Also there is a combination product that is a mix of both a preventative and curative fungicide, (Quilt, Stratego). When deciding which fungicide to use, timing is important, especially with the preventative fungicides. When disease conditions are favorable, the optimum timing for all fungicides is usually between stages 9 (flag leaf fully emerged) to 10 (full boot), says Bob Hunger, OSU Extension wheat disease specialist. All of the fungicides can be applied as late as growth stage 10.5 though, which is when heads are completely emerged. Finding the early symptoms of disease infection is not always easy. Early infections are very difficult to recognize, and it may be 5 to 10 days or more after infection before you'll actually see rust pustules developing on the leaves, states Eric DeWolf, K-State wheat disease specialist.

Obviously weather is a major factor in how foliar diseases progress. Mild weather (50 to 75 degrees) with some humidity is favorable to increasing stripe rust, but hot, windy conditions impede its development. Warmer weather (65 to 80 degrees) with humidity promotes leaf rust development.

Wheat variety also has considerable influence on yield loss. Susceptible varieties easily succumb to rust infections and lose flag leaf area. Resistant varieties may exhibit some rust pustules, but these pustules develop slowly and do not dramatically increase in number. For a complete listing of wheat varieties susceptible to diseases, check with your Extension office.

Last year, fungicide tests were conducted in southwest Kansas. Leaf rust was the main leaf disease at these sites in 2007. Quilt was applied at the flag leaf to boot stages in all cases, and the flag leaf was free, or nearly free, of disease at the time of application in all cases. A summary of the results taken from three counties at five sites consisting of several different wheat varieties in southwest Kansas showed that untreated wheat had an average yield of 33 bushels per acres with a test weight of 54.5 pounds per bushel while the fungicide-treated wheat had an average yield of 41 bushels per acre with an average test weight of 55.9 pounds per bushel.

Oklahoma State University has conducted more than 20 years of fungicide trials, including years with little or no disease and several years with high disease pressure. That research has documented an average yield increase of about 10 percent from using fungicides.

Last year in Kansas there were a few tests where a fungicide was sprayed on wheat that had been freeze-damaged. In some cases it worked in other cases it did not. Where fungicides had some effect on freeze-damaged wheat, it was mostly on wheat that was either late enough to have escaped the worst of the injury or on wheat that had lost its primary tillers quickly and re-grew from secondary tillers. At the North-Central Experiment Field in Belleville a fungicide was applied to freeze-damages Overly. Untreated wheat yielded 65 bushels and the fungicide treated wheat yielded 75 bushels.

Although the wheat hasn't started to green up yet this year, but with good moisture conditions across much of the state there could be some rust problems again this year. Obviously, it is too early to know, but we'll have to monitor the fields for disease infestations and watch how diseases progress from the south.

Further information on leaf rust and fungicide efficacy ratings can be obtained at www.oznet.ksu.edu or stopping by our office at 601 Main.

Stacy Campbell is the Extension Agriculture agent for Ellis County.