Fungicide Use in Alfalfa Production

Fungicide applications are commonplace in corn and soybean management to help protect plant health and reduce stress during grain fill. Fungicide use in alfalfa may not be as common, but research indicates it can offer similar benefits, resulting in better leaf retention, healthier plants and higher yield potential. 

Fungicides and Yield Potential 

If you’re aiming to boost yield potential, fungicides may come in handy for you. Trials conducted at Iowa State University (ISU) and the University of Wisconsin (UW)-Madison both showed promising results. After 6 years of testing fungicide applications on four cuttings per season, ISU researchers found an average of 8.3% increase in yield when a fungicide was applied compared to the control.1
The study at UW-Madison, which was conducted over 4 years, found an average yield gain 0.11 tons of dry matter (220 lbs.) per acre per cutting when applying Headline® fungicide and 0.05 tons of dry matter (100 lbs.) per acre per cutting when applying Quadris® fungicide despite relatively low disease levels across trials. 2 

Fungicides and Leaf Retention 

Fungicides also support plant health with improved leaf retention. As alfalfa matures, ethylene, a plant hormone that promotes ripening and maturity, increases in the older, lower canopy of alfalfa plants, resulting in high levels of leaf loss and increasing instances of leaf spots and disease. Fungicides like Headline® and Priaxor® work to slow down ethylene production and increase retention of the valuable alfalfa leaves producers work hard to retain.

What to Know Before You Spray 

While the yield results may look enticing, it’s important to weigh a few additional factors before heading to the field with a tank of fungicide.
  • Hay Prices: That 8.3% increase in yield doesn’t mean nearly as much when hay is at $80/ton compared to $200/ton.
  • Climate: Trials show the wetter the climate, the better the chance of achieving a profitable response to fungicide application.
  • Cutting Number: Studies show on average the first crop or harvest provides a higher percent yield response rate to fungicide application than for later crops.
  • Disease Resistance: If you’ve already invest in genetics with advanced disease resistance, a fungicide investment is not as likely to result in a beneficial return because your crop already has built-in protection.

Fungicide Timing 

Fungicides are labeled in alfalfa for up to three applications during the growing season. While we may have three allowances per growing season, even a single fungicide application in the spring can benefit and protect an alfalfa stand. A spring application of fungicide is generally the best time to treat alfalfa, as spring is when we face the most disease pressure with cool, wet conditions in the field. Utilizing fungicides throughout the season can also help alfalfa improve its stress tolerance, initiate faster regrowth between cuttings, reduce winter mortality and increase spring stem counts the following year. 
Fungicides can also tank mix with Roundup® herbicide and insecticides. When you do your spring field clean-up to relieve weed and insect pressure, add in a fungicide to help protect your alfalfa crop from disease pressure. 

Be sure to apply fungicide at the right canopy height. It’s ideal to treat first crop alfalfa at 6- to 8-inch canopy height as this will take advantage of its longer regrowth period before harvest.

Making The Fungicide Decision

To summarize the research, the highest probability of an economic response trends toward crops grown earlier in the season and with higher market value but deciding on fungicides is not a simple yes or no. All of the above factors must be taken into consideration. For additional guidance regarding fungicide use in alfalfa or America’s Alfalfa®, contact your local America’s Alfalfa dealer.

1 Smith, D. L., Chapman, S., Jensen, B., Blonde, G., Halfman, B., & Undersander, D. (2015). Using Fungicides on Alfalfa for Dairy Production in Wisconsin. The University of Wisconsin–Madison Extension.
2 Lang, B. (2017). Foliar Fungicides for Alfalfa Production: A Six-Year Summary. Iowa State University, Northeast Research and Demonstration Farm.
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