Turf professionals are constantly battling various obstacles in their quest to produce high-quality turf. One of the biggest challenges in highly maintained turf is the battle against turfgrass diseases. To prevent and cure various turfgrass diseases from destroying fine turfgrass systems, professionals apply fungicides regularly. 

With fungicide usage being as important as it is, let’s dive in and look at best practices to prevent fungicide resistance from being your next big headache. Here are a few basic concepts to remember when applying fungicides and developing a fungicide program:

What is the mode of action (MOA) of the fungicide? 

There are two basic MOA’s: contact and systemic. Chemistries such as chlorothalonil and fluazinam are currently the workhorses in the contact fungicide world, providing knockdown control and prevention of many pathogens by simply being present on the leaf blade of the turf. Contact fungicides are not absorbed or taken into the plant tissue. In general, there is very little disease resistance concern with contact fungicides. 

The other MOA grouping is systemic fungicides. Simply put, these chemistries are absorbed into the plant tissue, thus providing plant protectant properties against pathogens. The significant majority of fungicides in the turf market now, both old and newer chemistries, fall into the systemic category. These are the chemistries that are more likely to develop resistance.

What chemical family does the fungicide fall into? 

This is a key question to answer. Chemical families basically group similar chemical compounds with common traits. Some chemical families are prone to more resistance than others. A great way to dive into this more is to use resources published by local universities and extensions. The Families of Fungicides for Turfgrass from Ohio State University is a great one to reference.

What is the FRAC code of the fungicide?

While all fungicides are part of a chemical family, they’re also all assigned a FRAC code. The FRAC code is assigned to a chemistry by the Fungicide Resistance Action Committee. The codes are assigned to chemical families, making it pretty easy to identify products in the same family. The codes are commonly noted on product labels and packaging. By rotating FRAC codes regularly, you can easily avoid overusing a specific chemical family.

What is the chemistry’s common name? 

It’s imperative to understand what the fungicide’s common name is. The common name is the way the chemistry is classified into a family with similar compounds and FRAC code. The common name of the chemistry is listed on the label with the active ingredient percentage. Conversely, the trade name is what a specific manufacturer uses to market its product.

Key Takeaways

The key to rotating chemistries and thus preventing fungicide resistance is paying close attention to the chemistry details. Understanding the MOA, the chemistry’s common name and family, and the FRAC code will help you rotate different fungicides to avoid overuse and potential disease resistance in your fungicide program.