In this 2-year field study, four chemically diverse fungicides (i.e., chlorothalonil, boscalid, iprodione, and propiconazole) were evaluated for their ability to control dollar spot (Sclerotinia homoeocarpa) in creeping bentgrass (Agrostis stolonifera) as affected by simulated rain and mowing timing. Simulated rain (25 to 32 mm) was imposed about 30 min after fungicide application and was compared to rain-free plots. One set of plots was mowed in the morning when the canopy was wet with dew and compared to plots that were mowed when the canopy was dry in the afternoon. The percent reduction in dollar spot control associated with simulated-rain versus rain-free treatments in 2007 and 2008, respectively, was as follows: chlorothalonil 67 and 83%; propiconazole 42 and 79%; boscalid 48 and 70%; and iprodione 33 and 66%. When disease pressure was low, all fungicides subjected to simulated rain provided effective dollar spot control for 7 or more days following the initial application in each year. Across all fungicide-treated plots over 2 years, the average percent reduction in dollar spot associated with morning mowing ranged from 54 to 65%. The reduction in dollar spot severity in morning-mowed plots improved the performance of all fungicides.

Ethephon is commonly tank‐mixed with trinexapac‐ethyl (TE) and applied to putting greens in spring to manage annual bluegrass (Poa annua L.) seedheads. Previous research indicated that ethephon can predispose fairway‐height creeping bentgrass (Agrostis stolonifera L.) to scalping. It would be prudent to determine if ethephon has similar effects on creeping bentgrass maintained as a putting green. This study was conducted on a mature stand of ‘Providence’ creeping bentgrass grown on a sand‐based rootzone and maintained as a putting green. In 2007 and 2008, ethephon (3.8 kg ai/ha) and TE (0.045 kg ai/ha) were applied alone or in tank‐mix combination either once or twice beginning in April. Scalping first became evident on a consistent basis in early June about 38 days following the second ethephon application in each year. Two applications of ethephon alone or tank‐mixed with TE resulted in significant scalping that persisted from 35 to 56 days. Plots treated twice with ethephon exhibited reduced quality for 28 to 84 days. Golf course superintendents should be made aware of the potential level and time period that ethephon can predispose putting green height creeping bentgrass to scalping.

The importance of spray volume and application timing of a fungicide targeting dollar spot (Sclerotinia homoeocarpa F. T. Bennett) has been investigated, but with conflicting results. The objectives of this field study were to assess the influence of two spray volumes (468 and 935 liters water/ha) and two application timings (AM to a canopy wet with dew versus PM to a dry canopy) for fungicides targeting dollar spot curatively. Chlorothalonil (8.5 kg a.i./ha), propiconazole (0.5 kg a.i./ha), and a tank‐mix of chlorothalonil + propiconazole were compared on fairway height stands of ‘Crenshaw’ (2007 and 2008), ‘Backspin’ (2008), and ‘Providence’ (2009) creeping bentgrass (Agrostis stolonifera L.). There were no spray volume differences in 2007 or 2009. In 2008 in Crenshaw, there was less dollar spot in chlorothalonil‐treated plots using the low versus high spray volume, but the opposite occurred in Backspin. Less dollar spot developed in propiconazole‐treated plots subjected to the low versus high spray volume in Crenshaw in 2008. Higher levels of dollar spot developed in plots treated with propiconazole in the PM compared to the AM in 2009. The tank‐mix of chlorothalonil + propiconazole was unaffected by spray volume or application timing at all sites. The preponderance of data indicated that the curatively applied fungicides generally provided similar levels of dollar spot control at the two spray volumes and application timings evaluated.