Building upon the information provided by Hollingsworth and Holen on estimated returns observed from actual fungicide trials conducted in 2006, there is a method that has been suggested for estimating potential returns from a wheat fungicide program. The analysis uses a simple cost-benefit formula to estimate the potential profit from applying a fungicide to control wheat diseases. Potential profit will vary with:

• the estimated preventable yield loss from
  applying the fungicide,
• yield potential of the crop, affected by agronomic practices and the environment (e.g., rainfall, temperature).
• wheat price, affected by market forces and crop quality
• and, the cost of buying and applying the fungicide.

The cost-benefit formula is:

(PYL x YP x SP) – FAC = PP

where:
     PYL = Preventable Yield Loss (%)
     YP = Yield Potential (bu/ac)
     SP = Selling Price ($/bu)
     FAC = Fungicide + Application Cost ($/ac)
     PP = Potential Profit ($/ac)

Probably the hardest real world figure to decide on in the process is an estimate for preventable yield loss. It will depend on so many variables including, but not limited to, environmental conditions affecting disease development and the susceptibility of the wheat cultivar to diseases.

To try and keep it simple, yet illustrate a range of outcomes, Table 1 summarizes potential profit (PP) at prevented yield losses (PYL) of 10%, 15%, and 20% over a range of yields (YP) and three selling prices (SP). The table keeps the fungicide cost (FAC) constant at $16.00/acre. This analysis does not account for price premiums or discounts associated with quality factors such as test weight, DON (vomitoxin), damaged kernels, etc. For example, if timing of applications is incorrect, or inappropriate products or rates are used, the yield and quality response may not achieve the PYL expected.

Does it work ?
As stated previously, you are suppose to select values representative of real-life expectations. However the PYL might be difficult to pin down. Table 2 summarizes actual results obtained in on-farm trials conducted by Dr. Hollingsworth in 2005. The PYL’s in this study ranged from –30% to 22% when looking at scab protection with early flowering treatments. The high negative PYL was due to the no fungicide treatment yielding greater than the fungicide treatment for the variety Knudson. Complete results from the trial can be found at:

http://nwroc.umn.edu/Cropping_Issues/NW_Crop_trials/2005/
HRSW_disease_mngmnt.pdf  

* Source: Stephen Wegulo, Extension Plant Pathologist, U of Nebraska-Lincoln. Estimating the Potential Profit from a Fungicide Application to Control Wheat Diseases. Crop Watch News Service. May 18, 2007.