Factors to Consider When Choosing a Generic Fungicide for Field Crop Disease Management

Generic fungicides are fungicide products that contain off-patent active ingredients and are produced and marketed by a variety of chemical manufacturers. These products are now widely available for use in field crops. Generic fungicides are typically less expensive than the original patented product, and can be a lower-cost option for managing field crop diseases. However, choosing a generic fungicide involves more than matching a familiar fungicide active ingredient to a lower-priced alternative. This publication discusses considerations for using generic fungicides in field crops.

Compare active ingredients

The first step when evaluating a generic fungicide is to compare the active ingredient(s), not the product name. Before purchasing a product, compare the active ingredient name(s), Fungicide Resistance Action Committee (FRAC group(s), amount and percentage of each active ingredient, labeled application rate for the intended crop, labeled diseases, and approved application methods (e.g., ground or aerial). These comparisons help ensure the product is appropriate for the target disease and can be used legally under the intended application scenario. Readers unfamiliar with fungicide labels, FRAC groups, fungicide resistance or fungicide terminology are encouraged to consult the Crop Protection Network's Fungicide Use in Field Crops web book, particularly Chapters 1 (Fungicide Use in Field Crops) and 2 (Fungicide Chemical Classes), before comparing products.

This comparison is especially important for premix fungicides, or fungicides that contain two or more active ingredients. Two products may belong to the same FRAC groups while containing different active ingredients within those FRAC groups, different concentrations of those active ingredients, or different labeled application rates. For example, Aproach Prima contains picoxystrobin and cyproconazole, whereas RustEase contains azoxystrobin and cyproconazole. Although both products combine a QoI or strobilurin (FRAC 11) fungicide with a DMI or triazole (FRAC 3) fungicide, the specific QoI active ingredient differs. These differences should be considered when comparing products rather than assuming they are interchangeable.

Select the product based on the target disease

Fungicide selection should begin with the target disease. The Crop Protection Network fungicide efficacy tables provide disease-specific efficacy ratings for alfalfa, corn, soybean, wheat, and additional crops. These ratings are developed from replicated field trials across multiple years and locations across the US and are most useful when the product is applied with the recommended range of rates, timings, and with proper application methods. Before choosing a generic product, make sure the target disease is listed on the label, and active ingredients in the product are rated as effective for that disease on fungicide efficacy tables. Double check that you are comparing the exact active ingredient mix to that of the product you are trying to replace. It is important that you are comparing “apples to apples” when considering replacing a fungicide with a generic version.

Compare active ingredient delivered per acre

A lower price per gallon on a generic product does not always mean a lower cost per treated acre. Products with different concentrations may require different use rates to deliver similar amounts of active ingredient. When comparing products, calculate:

Product rate × pounds/grams (lb/g) active ingredient per gallon/liters = pounds/grams (lb/g) active ingredient applied per acre

For premixes, calculate each active ingredient separately. This step helps determine whether the generic and branded products are truly comparable and whether the generic product still provides a cost advantage after adjusting for labeled rate.

Many active ingredients are available both as individual products and as components of premixes. Consequently, farmers may unintentionally exceed the maximum seasonal use rate of an active ingredient by applying multiple fungicide products that contain the same chemistry. For example, an early-season fungicide application may include a premix containing active ingredient ‘A’. Later in the season, another fungicide application may also contain the same ingredient A (standalone or premix) and could potentially exceed the maximum per acre use rate. Tracking cumulative active ingredient use throughout the season helps ensure compliance with label restrictions while reducing the risk of resistance development.

Product formulation is important

The formulated product includes the active ingredient plus other ingredients that influence handling, mixing, stability, spreading, retention, uptake, rainfastness, and crop safety. Although fungicide labels list the percentage of active ingredient and the total percentage of "other ingredients," they generally do not identify the individual formulation components because they are considered proprietary. Pay close attention to formulation type (e.g., EC, SC, F, WG, or SP), tank-mix compatibility, adjuvant requirements, crop growth-stage restrictions, and other label directions. If two products contain the same active ingredient but different formulation types (for example, an EC versus an SC), read the label carefully because mixing order, compatibility, handling characteristics, and crop response may differ.

Finally, remember that crop injury (phytotoxicity) is generally associated with specific active ingredients rather than whether a fungicide is patented or generic. When switching between products, identify the active ingredient(s) in the formulation, as fungicides containing certain DMI active ingredients may increase the likelihood phytotoxicity under some environmental conditions or tank-mix combinations on certain crops. Additional information on recognizing and minimizing fungicide phytotoxicity in soybeans is available in the article, Fungicide Phytotoxicity on Soybean.

Other label differences

Products with the same active ingredient(s) may have different application intervals, application methods, seasonal maximum use rates, preharvest intervals (PHI), grazing or harvest restrictions, aerial application instructions, adjuvant requirements, tank mixture components, and state-specific registrations. These differences can influence both the legality and effectiveness of an application. Before purchasing or applying any fungicide, carefully read the current product label and ensure it is appropriate for the intended crop, disease, and application method.

Consider resistance management

Fungicide resistance management is an important consideration in product selections. Repeated use of active ingredients from the same FRAC group increases selection pressure on fungal and fungal-like pathogens. Generic and branded products with the same FRAC group place the same selection pressure on pathogens populations, so the same resistance management principles apply. These include rotating FRAC groups, limiting repeated applications of site-specific fungicides, avoiding reduced-rate applications, and using mixtures where each active ingredient contributes effective disease control.

Generic fungicides will manage disease

Generic fungicides are useful tools for managing field crop diseases, especially when they reduce cost without compromising disease control. Generic products should be selected using the same research-based process used for any fungicide, by choosing the right product for the target disease. This may require some additional time to compare labels of products to ensure that applications will have the desired effect for the target disease and production system. Seek out state-specific recommendations about generic product efficacy from your local Extension Specialists.

Acknowledgements

Authors

Tom Allen, Mississippi State University; Kelsey Andersen Onofre, Kansas State University; Carl Bradley, University of Kentucky; Boris Camiletti, University of Illinois Urbana-Champaign; Nicholas Dufault, University of Florida; Travis Faske, University of Arkansas; Daren Mueller, Iowa State University; Camilo Parada-Rojas, Cornell University; Alison Robertson, Iowa State University; Kiersten Wise, University of Kentucky

Reviewers

Andrew Friskop, North Dakota State University; Damon Smith, University of Wisconsin-Madison; Albert Tenuta, Ontario Ministry of Agriculture, Food and Agribusiness

How to cite: Allen, T., Andersen Onofre, K., Bradley, C., Camiletti, B., Dufault, N., Faske, T., Mueller, D., Parada-Rojas, C., Robertson, A., Wise, K. 2026. Factors to Consider When Choosing a Generic Fungicide for Field Crop Disease Management. Crop Protection Network. CPN-4014. doi.org/10.31274/cpn-20260713-0.