Evaluating the need for fungicides in wheat
Reports of low levels of stripe and leaf rust in Kansas are being reported. Reports to date have come from primarily south central and central regions of the state. Counties where stripe rust has been reported include: Harper, Kingman, Sedgwick, Pratt, Reno, McPherson, and Saline. The stripe rust in Kansas has been primarily observed on Everest and Armour. This is important because these varieties were previously thought to be resistant to stripe rust.
Leaf rust was observed at trace levels in Kingman, Ness, and Riley counties. Tan spot and other leaf spotting diseases are also being reported in many parts of Kansas. Tan spot is severe in some fields with considerable wheat residue left on the soil surface.
Wheat streak mosaic and barley yellow dwarf are also being reported in some fields. The reports of wheat streak to date have come primarily from central Kansas and a few from eastern Kansas. This viral disease is historically less common in these portions of the state, but can occur when volunteer wheat is left uncontrolled during the previous summer and fall.
Risk of Fusarium head blight (FHB):
There is a national effort to predict outbreaks of FHB based on weather conditions prior to flowering when wheat is most vulnerable to this disease. The prediction models available on-line are showing that considerable areas of central Kansas have moderate and high risk of disease. This is cause for concern, but is not critical during the boot stage of development. Farmers should be carefully monitoring the risk of FHB as the wheat moves into the heading stages of growth. I mention this now because management of FHB requires some modification to fungicide timing and influences product choice. You can find more information about the risk of FHB at: http://www.wheatscab.psu.edu/riskTool_2012.html
Evaluating the need for fungicides:
Producers should be checking their wheat fields for symptoms of disease and making plans for fungicide applications if disease is present. The activity of stripe rust and other diseases in Kansas is a cause of concern, suggesting at least a moderate risk of severe disease in 2012. Finding even low levels of disease on the top two leaves prior to flowering indicates a high risk of severe yield loss. Recent weather in central and south central Kansas has been favorable for continued disease development, further reinforcing the decision to apply a fungicide. Many fields have excellent yield potential this year and are worth protecting with fungicides. Seed production fields are also a top priority. For more information about fungicide decisions in wheat see our recent K-State publication, Evaluating the Need for Wheat Foliar Fungicides, MF-3057 http://www.ksre.ksu.edu/library/plant2/mf3057.pdf
The best time to apply a fungicide for leaf disease management is between flag leaf emergence and flowering. Most of the wheat in south central or central Kansas is already at flag leaf emergence and boot stages of development. This means that farmers have approximately 10-14 days to make fungicide applications. Applications targeting Fusarium head blight should be made after the wheat has fully headed.
There are many fungicides labeled for use on wheat. Nearly all fungicides provide very good or excellent control of foliar diseases. There is a significant difference in product costs, however, with products containing tebuconazole or propiconazole being the lowest cost options (often less than $4 per acre product costs). The triazole fungicides including Prosaro and Caramba are the best option for suppression of Fusarium head blight. More information about fungicide products can be found in the publication, Foliar Fungicide Efficacy for Wheat Disease Management, 2012, EP130. http://www.ksre.ksu.edu/library/plant2/ep130.pdf
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