Brian Aynardi, Ph.D., shares the newest fungicide innovation from PBI-Gordon. Aynardi is the Northeast Research Scientist for PBI-Gordon, and leads the fungicide development effort at PBI-Gordon. He can be reached at for more information.

Union™ Fungicide SC and its active ingredients, cyazofamid and azoxystrobin.

Union™ is premix fungicide of cyazofamid and azoxystrobin available as an SC (suspension concentrate) formulation. Cyazofamid, formulated and distributed as Segway® Fungicide SC by PBI-Gordon Corporation, was first discovered in 1987 by ISK (Ishihara Sangyo Kaisha, Ltd.). Cyazofamid belongs to the QiI (quinone inside inhibitor) group of fungicides (FRAC group 21), which disrupt the electron transport chain at the inside binding site of complex III of the cytochrome B. Cyazofamid is the only fungicide from the cyano-imidazole group registered for use in the United States on turf and ornamentals.

The second active ingredient in Union fungicide is azoxystrobin, which was the first of the strobilurin fungicides to be registered for turf in the United States, in 1997. Strobilurins, or QoI (quinone outside inhibitor) fungicides (FRAC group 11) are very similar to QiI fungicides in that they disrupt the electron transport chain at complex III of the cytochrome B, but they do so at the outside binding site.

1What diseases does Union effectively control?

Union fungicide is the ultimate premix product for control of the pathogens inciting Pythium diseases. Cyazofamid (Segway® Fungicide SC, PBI-Gordon Corp.) has been the premier active ingredient of choice for control of the various Pythium species affecting turfgrass, most notably those causing Pythium root rot, Pythium blight, and Pythium root dysfunction. The addition of azoxystrobin to cyazofamid offers a second mode of action for control of the various pathogens causing Pythium diseases commonly found in the turf industry.

Cyazofamid (Segway®) only controls diseases caused by oomycete fungi. Therefore, control of the other pathogens listed on the Union label can be attributed to azoxystrobin. Turfgrass managers can expect excellent control of the following diseases, provided resistant populations of the pathogens causing these diseases are not present: anthracnose, brown patch, fairy ring, large patch, leaf spot (Drechslera and Bipolaris spp.), gray leaf spot, and summer patch.

Union fungicide is labeled for use on golf courses, athletic fields, commercial and residential lawns, sod farms, and parks.

2Where will Union best fit into fungicide programs?

Union has a unique fit to turfgrass managers’ spray programs, particularly as it relates to what diseases are most prevalent on their respective use sites. For example, for those who struggle with Pythium root rot, Union is an excellent preventive application once soil temperatures at the 2" depth are in excess of 65°F. These are the same temperatures other soil-borne fungi become (or are already) active, such as the pathogens causing summer patch and fairy ring.

Among the most problematic diseases on commercial and residential lawns comprised of cool-season turfgrass are leaf spots, Pythium blight and brown patch. Union provides control of the pathogens causing these diseases. Likewise, diseases of warm-season turf such as large patch, Pythium blight, and leaf spots are also controlled with preventive applications of Union.

Union is ideal for superintendents managing ultradwarf bermudagrass greens, where heavy rains associated with cooler weather result in Pythium blight and leaf spot concerns. Union is a premix product that controls both pathogens and the subsequent disease as a single product. An application of Union fungicide gives superintendents peace of mind, knowing control of both diseases is covered in the event of misdiagnosis.

3How do we minimize the risk of developing resistance with Union?

Rotation is very important when using site-specific modes of action. Make sure not to apply more than two consecutive applications of Union, and no more than two consecutive applications of any QoI (FRAC group 11) or QiI (FRAC group 21). For example, Union should not be applied twice and preceded or succeeded with an application of Segway, nor should Union be applied more than once if a strobilurin fungicide is applied in the spray immediately before or after a Union application. Remember to always look at premix products being applied before or after Union to verify if they contain a strobilurin; just because it is part of a premix product does not mean it does not count as a FRAC group 11 application.