Iron sulfate and lightweight rolling for dollar spot

Effect of FeSO4 and lightweight rolling on dollar spot suppression. (Photo: Travis Roberson)

Dollar spot (Clarireedia spp.) is one of the most damaging turfgrass diseases worldwide. Superintendents routinely apply a wide variety of broad spectrum and site-specific fungicides to suppress dollar spot, but there are increasing alternatives to traditional fungicides employed for dollar spot management.

Iron sulfate (FeSO₄) applications and/or rolling offer potential nonfungicidal treatments for reducing dollar spot. A study was conducted on an L93 creeping bentgrass (Agrostis stolonifera) fairway at Virginia Tech to assess the effect of FeSO₄ applications at 0.5 lb./1,000 ft², lightweight rolling three times per week, lightweight rolling six times per week, FeSO₄ at 0.5 lb./1,000 ft² plus lightweight rolling three times per week and FeSO₄ at 0.5 lb./1,000 ft² plus lightweight rolling six times per week on dollar spot suppression.

Results illustrated that FeSO₄ alone reduced dollar spot counts by more than 64 percent compared with nontreated plots. Furthermore, lightweight rolling three times per week did not reduce dollar spot counts, while lightweight rolling six times per week reduced dollar spot counts 58 percent compared with nonrolled plots. There were no additive or interactive effects of lightweight rolling in conjunction with FeSO₄ applications in this study.

Both frequent lightweight rolling and FeSO₄ applications clearly are effective dollar spot suppression strategies. However, FeSO₄ at 0.5 lbs./1,000 ft² is ~$13/acre is theoretically much more cost effective than the time and labor it takes to lightweight roll fairways six times per week. The implementation of dollar spot management techniques such as these could potentially save money and reduce the number of fungicide applications necessary for dollar spot suppression, thereby reducing the risk of fungicide resistance. Work is currently being done on ways to optimize FeSO₄ applications targeting dollar spot.

Wendell Hutchens and David McCall, Ph.D., are at Virginia Tech University, and Travis Roberson is at Willow Oaks Country Club, Richmond, Va. You may reach Wendell Hutchens at wendelljh@vt.edu for more information.