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DMI Fungicide Use on Creeping Bentgrass during Heat Stress

August 15, 2007
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Golf course superintendents must use extreme caution when applying DMI fungicides (Banner, Bayleton, Eagle, Rubigan, Trinity) to creeping bentgrass putting greens.  These products can cause severe phytotoxicity, thinning, and even death of creeping bentgrass if the turf is severely stressed from heat, drought, or other factors. The potential for injury is much greater when high label rates are used and when high temperatures are consistently above 90F. 

There are differences among the DMIs in their potential to cause injury - some are safer than others - but none of the currently available DMIs can be classified as "safe" on bentgrass during 90+ degree weather.

In addition, there are few situations where DMI applications are necessary or beneficial during the summer, as safer chemistries are available for control of most summer diseases. The DMIs are most useful during the fall and spring to prevent diseases like dollar spot, summer patch, take-all patch, fairy ring, snow mold, yellow patch, etc.

Anthracnose is the only disease that warrants DMI applications during the summer, but this is only a concern for superintendents managing older bentgrass varieties like Penncross, Pennlinks, Dominant, Dominant Plus, L-93, and Crenshaw. If a DMI application is necessary to control anthracnose during the summer, use low label rates and tank-mix with chlorothalonil to prevent algae infestations. The Penn A and G series bentgrasses are essentially immune to anthracnose in North Carolina so this disease is not a concern for superintendents managing these grasses.