Foliar Fungicides in Alfalfa

With all the talk on fungicide use in corn and soybean, this may be a good time to talk about alfalfa production and fungicide use. We often get asked as Extension field agronomists about studies conducted with fungicides on crops. So, the short answer to fungicide use on alfalfa is “it depends”, but we have good research on helping farmers understand when to put the odds in their favor. 

Iowa State University Extension and Outreach conducted 14 site years on 179 fungicide treatments by harvest comparisons. These studies were conducted at the Northeast Iowa Research Farm near Nashua. I will summarize a few talking points and takeaways about the project and foliar fungicide applications in alfalfa below.

• It is important to know the variety’s susceptibility to disease. Varieties with excellent disease ratings are less likely to respond to fungicide.
•  Weather does play a big role in response to fungicides. Remember the 2012 drought?  Fungicides are less effective in years with drier than normal precipitation. Wet and abnormally high precipitation will increase the odds of a return because the precipitation helps to provide a more favorable environment for diseases to develop.
• First cutting alfalfa tends to respond the most to fungicide applications.  Later applications in the year even with high moisture and or following a hail event do not respond as well. 
• Application timing is important as the fungicide only protects the leaves it touches. In alfalfa, usually 6-8” alfalfa is the target timing due to the harvest interval for fungicides. Always check the label of what you plan to  apply.
• It’s also important to account for the value you place on the price of alfalfa. Dairy producers rely on quality and place more value on alfalfa per ton, so more likely to value the fungicide application. Make sure to use current application and product costs when calculating the value of fungicide application.   You can see from the study when the application cost was included the return was less. Often, after the first cutting it was only a 50 percent chance of a return. 

For all details about the project read the project summary linked here: https://www.extension.iastate.edu/dairyteam/files/documents/Alf%20Fung%204-yr%20sum.pdf