Dollar spot (DS), caused by Sclerotinia homoeocarpa F. T. Bennett, can be a difficult disease to control in creeping bentgrass (Agrostis stolonifera L.). The objectives of this three‐year field study were to: (i) assess the influence of two spray volumes (468 and 1020 liters of water per ha); and (ii) evaluate the impact of the presence or absence of dew at the time of application on the ability of chlorothalonil, propiconazole, and a tank mix of chlorothalonil and propiconazole to control DS in fairway‐height creeping bentgrass. Chlorothalonil provided better DS control when applied to a dry canopy after 12:00 h, when compared to AM applications. Chlorothalonil generally provided better DS control when applied in 468 versus 1020 liters of water per ha; however, there were no rating dates when chlorothalonil provided more effective DS control when applied in 1020 liter/ha. On several 2004 rating dates, chlorothalonil applied in the AM with dew displaced provided better DS control than the AM application with dew present. The presence or absence of dew and the two spray volumes assessed did not affect the level of DS control provided by propiconazole or a tank mix of propiconazole and chlorothalonil. The amount of AM dew present in the canopy ranged between 982 and 2,548 liter/ha. Chlorothalonil performance likely was reduced as a result of being diluted or washed from foliar surfaces in the high spray volume or diluted by dew. Since both fungicides performed well when applied in 468 liters of water per ha, golf course managers can use the lower spray volume to save time, labor, and fuel.

Annual bluegrass (Poa annua L.) (ABG) is considered by many turfgrass managers to be an intractable weed problem, particularly in creeping bentgrass (Agrostis stolonifera L.) (CBG) fairways. Bispyribac‐sodium (BPS) is labeled for the control of ABG, but it can elicit objectionable levels of chlorosis in CBG. Little information exists regarding the longevity of chlorosis, other potential phytotoxic effects or the ability of BPS to control ABG in CBG. The primary objectives of this field study were to determine if the chlorosis elicited by BPS could be masked by tank‐mixing the herbicide with a chelated iron plus nitrogen product and to determine an effective BPS rate for controlling ABG. Bispyribac‐sodium was applied to mature fairway height CBG three times at 49 and 111 g ai/ha and two or three times at 74 g ai/ha on a two‐week interval. Chlorosis appeared within one week and generally persisted for 14 to 21 days, but there was no BPS rate effect on the level or longevity of the CBG chlorosis. Tank‐mixing BPS with Fe + N effectively masked the chlorosis, regardless of herbicide rate. All BPS rates and timing provided similar levels (≥ 82%) of ABG control.

Establishing creeping bentgrass [Agrostis stolonifera L. (CBG)] and perennial ryegrass [Lolium perenne L. (PRG)] from seed can be hampered by competition from annual bluegrass (Poa annua L.). Bispyribac-sodium (BPS) is a postemergence annual bluegrass herbicide that may have applications for use when establishing these grasses. This field study was undertaken to determine if BPS could be applied safely to CBG and PRG seedlings. Ethofumesate (ETHO) was applied sequentially (840 + 840 g·ha−1 a.i.) and served as a standard. In 2004, BPS was applied once (49, 74, 111, and 148 g·ha−1 a.i.) or sequentially (49 + 49 and 74 + 74 g·ha−1 a.i.) to CBG and PRG seedlings 4 weeks after emergence in Maryland. In 2004, BPS discolored CBG and PRG and reduced PRG cover, whereas ETHO reduced CBG cover but was not injurious to PRG. In 2005, a single (148 g·ha−1 a.i.) and sequential (25 + 25, 49 + 49 and 74 + 74 g·ha−1 a.i.) applications of BPS were made to CBG and PRG 2 and 4 weeks after seedling emergence (WASE) in Maryland and Connecticut. Treatments applied 2 WASE generally resulted in more injury when compared with applications made 4 WASE. In Maryland in 2005, CBG only sustained long-term loss of cover when treated 2 WASE with 148 g·ha−1 a.i. of BPS. The PRG was more sensitive to BPS and 148 g·ha−1 a.i. applied once and sequential treatments 49 g·ha−1 a.i. or greater applied 2 and 4 WASE generally caused the greatest loss in PRG cover. Conversely, CBG was severely injured by all BPS treatments and ETHO in Connecticut. In PRG, only 25 + 25 g·ha−1 a.i. of BPS and ETHO in both timings did not cause a loss in cover in Connecticut or Maryland. High levels of precipitation and probably other unknown factors may have enhanced the phytotoxicity observed in Connecticut. Ethofumesate generally was safer than BPS for use on PRG seedlings.

Creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw.] and perennial ryegrass (Lolium perenne L.) are commonly grown fairway grasses that are susceptible to dollar spot (Sclerotinia homoeocarpa F. T. Bennett; DS) and gray leaf spot [Pyricularia grisea (Cooke) Sacc; GLS.] diseases, respectively. This field study assessed the influence of two irrigation regimes (light and frequent nighttime versus deep and infrequent morning irrigation) and six chemical treatments including: chlorothalonil (tetrachloroisophthalonitrile), paclobutrazol [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol; PB], wetting agent (polymeric polyoxyalkylene 95% oxoalkonyl hydroxyl polyoxlalkane diyl 5%; WA), chlorothalonil 1 PB, chlorothalonil 1 WA and chlorothalonil 1 PB 1 WA on DS and GLS severity over a 3-yr period. Dollar spot was more severe in late summer in creeping bentgrass that received deep and infrequent versus light and frequent irrigation in 2002 and 2004 and disease severity was negatively correlated with volumetric soil moisture (r 5 20.77 to 20.96). Soil moisture levels above 0.25 cm 3 cm 23were associated with an improved ability of chlorothalonil, PB, and WA to suppress DS, but they had no effect on GLS. In 2002, GLS rapidly and severely damaged even fungicide-treated plots, and there was no irrigation effect. In 2004, gray leaf spot was more severe in light and frequent nighttime irrigated blocks versus deep and infrequent morning irrigated blocks. Chlorothalonil (8.0 kg a.i. ha 21) provided effective GLS control when applied on an 8-d interval in 2004 but only in infrequently irrigated blocks where disease pressure was less.

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