Virginia Turfgrass Journal - July / August 2017

Page 22

Feature Story

DOLLAR SPOT SUPPRESSION = Chlorothalonil + Ferrous Sulfate By Camden D. Shelton, MS candidate; David S. McCall, Ph.D., Turfgrass Pathology; Erik Ervin, Ph.D., Turfgass Scientist; and Shawn D. Askew, Ph.D., Weed Scientist, Virginia Tech

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hlorothalonil, applied alone or in combination with other fungicides, is often used for preventive or curative control of dollar spot on creeping bentgrass. Golf course superintendents relying on chlorothalonil may find that restrictions on its use prevent them from achieving desirable levels of dollar spot control throughout the season. Ferrous sulfate applied at 1 lb. product/1,000 ft2 has also been found to control dollar spot. The objective of this research was to determine whether combining ferrous sulfate and lower

rates of chlorotahlonil could result in acceptable dollar spot control. We conducted our research in 2016 on a 007 creeping bentgrass putting green and L-93 creeping bentgrass fairway in Blacksburg, VA. Treatments included Daconil WeatherStik (chlorothalonil) applied at rates of 1, 2, 3 and 4 fl. oz./1,000 ft2 with or without FeSO4 (20% ferrous sulfate-heptahydrate) applied at 1 lb. product/ 1,000 ft2. Using a conservative estimation method, chlorothalonil rates were reduced by 1.4 kg ai/hectare under heavy pressure (putting green) and 3.1 kg

Dollar spot suppression with 2 fl. oz. chlorothalonil.

22 | VIRGINIA TURFGRASS JOURNAL July/August 2017 www.vaturf.org

ai/hectare under mild pressure (fairway). In related studies, ferrous sulfate extended the longevity of chlorothalonil by five days, and ferrous sulfate rates were cut in half (0.5 lb product/1000ft2) without sacrificing control (see page 20). Studies are being continued this year with reduced rates of ferrous sulfate and chlorothalonil. This article previously appeared in the February 2017 issue of Golf Course Management magazine.

Dollar spot suppression with 2 fl. oz. chlorothalonil + 1 lb. FeSO4.