Researchers from Clemson University evaluate fungicides that reduce spring dead spot in fairway bermudagrass

Researchers at Clemson University evaluated fungicides for preventive control of spring dead spot disease caused by Ophiosphaerella spp. In the fall of 2019, they initiated the study at Florence Country Club in Florence, S.C., on a bermudagrass fairway constructed on sandy loam soil.

Fungicide control of spring dead spot in bermudagrass fairways. Researchers applied fungicides on Oct. 29 and Nov. 25, 2019, and collected disease ratings the following spring, 2020. Bar values are the means of four replicates, and means followed by the same letter are not significantly different.

The researchers arranged treatments in 6-by-10-foot plots in a randomized complete block design with four replications. They applied treatments as a foliar spray in water equivalent to 2.1 gallons per 1000 square feet using a CO2-powered walk-behind sprayer equipped with dual TeeJet 8002 nozzles.

The treatment applications on Oct. 29 and Nov. 25, 2019, received 0.125 post-application irrigation. The trial area was rated the following spring for spring dead spot development as a percent turf area affected. They also used these ratings to calculate each treatment’s area under disease progress curve (AUDPC) values.

They chose an area of the golf course based on previous spring dead spot outbreaks, and symptoms were readily observed by late March, 2020. Disease pressure was moderate, with roughly 20 percent severity observed in the non-treated control on May 5, 2020.

The results of all rating dates show fungicides significantly reduced spring dead spot symptoms compared to the non-treated group (Figure 1). The bar values are the means of four replicates, and means followed by the same letter are not significantly different.

When comparing AUDPC values with the non-treated control (709.7), Maxtima (mefentrifluconazole) applied at 0.8 fl. oz. per 1000 square feet showed the best overall control (103.2) but was not different than Maxtima at 0.6 fl. oz. per 1000 square feet (138.3) or Posterity (pydiflumetofen) at 0.16 fl. oz. per 1000 ft2 (153.2). By May, both Maxtima rates performed better than Torque (tebuconazole).

Reference

The article is adapted from Roberts, J.A., McBride, L., and Lynn, A. 2020. Evaluation of fungicides for prevention of spring dead spot disease in bermudagrass fairway turf. Plant Disease Management Reports 15:T034.