Pre-packaged fungicide combination products can be great time savers for turf managers. They can also be a prescription for fungicide overuse or under use. Whether or not a pre-packaged product is the right choice for the job depends on if the diseases you need to control match the concentrations of each ingredient in the product. Sadly, doing the calculations needed can take the convenience right out of a combo package, says PACE Turf’s Larry Stowell, Ph.D. To make the job easier, Stowell has posted a “Product Active Ingredient Calculation Spreadsheet” and companion Reference Table available for free download in the “Announcements” section of the PACE Turf website at

Wendy Gelernter, Ph.D., who founded PACE Turf with Stowell, urges turf managers to calculate, calculate, calculate. “It’s that important. If the component fungicides have been packaged in the right concentrations and ratios for the pests you want to control, then you are in luck. But if not, then you run the risk of either poor control (if there isn’t enough of one or more fungicides) or of overuse and unnecessary expense (if one or more of the fungicides is at a higher concentration than you need).”

Some materials, such as chlorothalonil, have restrictions on the amount that can be used per year. In those cases, “it is even more important to know how much active ingredient is being applied in each application,” Gelernter says.

Convenience is the best reason to use a pre-packaged combination product, according to Gelernter and Stowell. In addition to saving time by targeting multiple diseases with a single application, they can also remove some of the guesswork associated with fungicide compatibility, since pre-packaged products should be both physically and chemically compatible. Yet as more combination products reach the marketplace, more and more reasons for justifying their use are being proposed. These include avoidance of the development of fungicide resistance, as well as the potential for synergy – a phenomenon that occurs when products that are combined result in better control than would have been predicted. “These benefits are theoretically possible,” Stowell says. “However, there just isn’t enough data to support either of these claims at this time. For this reason, convenience should be the driving force in a decision to use a combination product.”

PACE Turf is a membership organization that provides research, education and information services to the turf management community. Founded in 1993 by Wendy Gelernter, Ph.D. and Larry Stowell, Ph.D., the PACE Turf mission is to provide expert, science-based advice to turf managers so they may develop management programs that are effective, economical and agronomically sound. For more information, visit


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