Impact of Rainfall and Warm Temperatures on Snow Mold Fungicides

In the northern tier of the country, warm temperatures often extend the growing season and mowing well into November and even December in some parts of the country. Additionally, select areas often experience significant rainfall or snow melt after the final snow mold fungicide application. Below are a few key considerations to ensure adequate protection from snow mold.

• Fungicide persistence - In the linked article from the August 2015 issue of GCM Magazine, Dr. Paul Koch highlights his research conducted on snow mold fungicide persistence. Water from rainfall or snow melt is a primary factor reducing fungicide persistence. Other factors include plant growth (mowing) and above average soil temperatures, which increases microbial activity and subsequent product degradation
• Set-up app - An initial DMI fungicide application at 50-65°F air temperature will help reduce snow mold inoculum (sclerotia start germinating at these temperatures), and can help to ensure better efficacy from your final snow mold application, especially through difficult winters. This application is usually 2-4 weeks prior to the final application and includes a DMI fungicide like Envu’s new Densicor^® which has shown to be highly effective for this application
• Hold off on the final application - Until top growth ceases to minimize fungicide loss in clippings
• Consider reapplying in the most sensitive areas (greens, tees and historically damaged areas) IF:
• The last planned application was made and growth/mowing has continued
• Significant rainfall (~2”) has occurred since your final snow mold application
• Impossible to predict long term effects - The exact amount of warmth, growth, rainfall or snow melt required to significantly reduce efficacy of snow mold fungicides is impossible to predict, so it is best to error on the side of safety to ensure a successful start to the 2022 season
• Need more info? Contact your Envu area sales manager if you need assistance 

Rain and snow melt can reduce persistence of snow mold fungicides, consider reapplication if significant rainfall occurs after final application and permanent snow cover (Envu)