The ability to successfully apply fungicides will be critical if you are dealing with an outbreak of rust in your wheat crop this year. Some producers are indecisive on what to do. The decision to apply a fungicide should be impelled by the cost of the treatment, susceptibility of the varieties, presence of the disease and the outlook for the weather.
Currently, we are seeing moderate to high levels of leaf rust, low levels of stripe rust and low levels of powdery mildew. The producer needs to be educated on the characteristics of their wheat variety. If you have a resistant variety to these diseases, fungicide application can wait, but scouting your field should be continued on a weekly basis.
According to Kansas State University Plant Pathologist, Erick De Worf, stripe rust is favored by cool, humid weather and disease development is most rapid between 50 and 60 degrees Fahrenheit. The disease is inhibited when night time temperatures get above 68 degrees Fahrenheit or there are several days in a row in the mid-80s. Leaf rust is the most damaging when the upper leaves of infected plants become severely rusted before flowering. Heavy rusting causes early loss of the leaves, which reduces the grain filling period and results in smaller kernel size (Stephen N. Wegula, University of Nebraska-Lincoln Extension Plant Pathologist). The optimum temperature for infection in leaf rust is 59-68 degrees, and 68-77 degrees for disease development.
Foliar fungicides will effectively control rust. Products containing a triazole fungicide are considered the best option when the disease is established in the field (Prosaro, TebuStar, Tilt). Products belonging to the strobilurin class of fungicides (Headline) are most effective when applied before infection. The triazole class of fungicide is generally considered to have stronger curative activity (Wolf).
We are currently running two products for fungicide application, TebuStar and Prosaro. If you are finding rust on a field of seed wheat or wheat that normally yields higher in bushels, it would be wise to go with Prosaro. Prosaro is a curative and preventative giving you approximately 30 days of residual. If you have an average yielding field and you’re focusing on the economics of your crop, TebuStar would be a great option for that. It is a curative giving you a 7-10 day residual. These products need to be applied when there is flecking on the flag leaf and pustules on the lower leaves. Please keep in mind fungicide does not produce yield increases, but helps maintain what the crop has already formed.
While application timing is key, water volume is the most important application parameter when it comes to achieving good coverage. When applying fungicide with a row crop, we run 20 gallons of water. We work closely with NOE Aviation in Watonga, Okla for all of our aerial applications and strongly recommend running 3 gallon of water. You cannot put a price on good coverage. According to spray technology specialist, Tom Wolf, “increasing water volumes has a greater effect on fungicide performance than droplet size or spray pressure.”
Moving forward, now is the time to be planning for cover crops. We have a full line of cover crop options to choose from. Integrating cover crops into your farming practices is an effective way to improve your soil fertility by adding nitrogen back into the soil, reduce soil erosion, reduce run off and countless other benefits. Soil health benefits are often improved when using cover crops in combination with no-till. Please contact your local agronomist for seed or to help you get a plan for this summer.