Frequency and severity of anthracnose epiphytotics, caused by Colletotrichum cereale Manns Manns sensu lato Crouch, Clarke, and Hillman, on annual bluegrass (ABG) [Poa annua L. f. reptans (Hauskins) T. Koyama] putting greens have increased over the past decade. This 3‐yr field study evaluated the impact of N fertilization (4.9 kg ha−1 every 7 or 28 d), mefluidide (ME; 0 and 0.106 kg a.i. ha−1 yr−1) {N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide}, trinexapac‐ethyl (TE; 0 and 0.050 kg a.i. ha−1 every 14 d) [4‐(cyclopropyl‐α‐hydroxy‐methylene)‐3,5‐dioxocyclohexanecarboxylic acid ethylester], verticutting (VC; 0‐ and 3‐mm depth every 14 d), and interactions of these factors on anthracnose of ABG mowed at 3.2 mm. Nitrogen fertilization frequency had the greatest influence on disease throughout the study; N applied at 4.9 kg ha−1 every 7 d reduced damage 5 to 24% compared to a 28‐d interval. The plant growth regulators, ME and TE, frequently interacted during the last 2 yr of the study; sequential application of ME and TE reduced disease 6 to 14% compared to plots that only received one of these plant growth regulators. At advanced stages of disease, the combination of 7‐d N fertilization and ME and TE application had the greatest disease reduction. Verticutting had little effect on anthracnose severity.

Anthracnose (Colletotrichum cereale Manns sensu lato Crouch, Clarke & Hillman) has been a devastating disease on annual bluegrass (ABG) [Poa annua L. f. reptans (Hausskn.) T. Koyama] putting green turf over the past 15 yr. The objectives of this 2‐yr field trial on ABG were to evaluate the impact of mowing height (2.8, 3.2, and 3.6 mm), mowing frequency (seven and 14 times wk−1), lightweight rolling (none and every other day), and possible interactions of those factors on anthracnose severity and golf ball roll distance (BRD). Mowing height had the greatest effect on anthracnose. Mowing at 2.8 mm increased disease severity 3 to 21% compared with mowing at 3.6 mm, while 3.2 mm was intermediate to higher and lower heights. Mowing frequency had little effect on anthracnose, although mowing 14 times wk−1 occasionally reduced disease severity 1 to 14% compared with seven times wk−1 Rolling every other day also occasionally reduced disease severity 5 to 6% under moderate disease pressure. Mowing at 2.8 mm generally provided the greatest BRD. However, similar or greater BRDs were achieved at 3.2 and 3.6 mm, using combinations of increased mowing frequency and/or rolling compared with mowing at 2.8 mm seven times wk−1 without rolling. Thus, anthracnose severity on ABG greens can be reduced by raising the mowing height as little as 0.4 mm, and BRD (≥2.9–3.2 m) can be maintained by increasing mowing frequency and/or rolling without increasing disease severity.

Sand topdressing has been reputed to increase anthracnose caused by Golletotrichum cereale Manns sensu lato Crouch, Clarke, and Hillman on annual bluegrass (ABG) [Poa annua L. forma reptans (Hausskn.) T. Koyama] putting greens. Field trials were conducted to determine the effects of (i) frequent (7 d) and low-rate (0.3 L m"^) sand topdressing and brushing, (ii) infrequent (21 and 42 d) and increased-rate (1.2 L m"^) sand topdressing, and (iii) sand topdressing application intervals (7,14, and 28 d) and rates (0.3 and 0.6 L m"^) on anthracnose severity of ABG turf mowed at 3.2 mm. Topdressing every 7 d at 0.3 L m"2 initially enhanced disease (8%) during the first year of the trial; however, continued topdressing reduced anthracnose severity 17 to 47% later in 2006 and 3 to 26% in 2007 compared to nontopdressed turf. Topdressing every 21 and 42 d at 1.2 L m"^ reduced disease 4 to 28% over the 2-yr study; however, sand applied every 21 d reduced disease 5 to 13% more than the 42-d interval in 2007. Topdressing rate (0, 0.3, and 0.6 L m-^) and interval (7, 14, and 28 d) interacted to affect anthracnose severity in both years. Disease declined in a curvilinear manner as rate increased at the 7-and 14-d intervals each year. Increased rates applied every 28 d reduced disease linearly in 2006 and curvilinearly at rates exceeding 0.3 L m"2 in 2007. Topdressing every 7 or 14 d at 0.3 or 0.6 L m"2, respectively, provided the most rapid and effective anthracnose reduction and best turf quality.

The impact of plant growth regulators on anthracnose (Colletotrichum cereale) severity in annual bluegrass (Poa annua) putting greens has been a concern for turf managers. Two field studies assessed the influence of mefluidide (ME; applied twice at 0 or 0.69 fl oz/1000 ft2) or ethephon (EP; applied twice at 0 or 5.0 fl oz/1000 ft2) and three application intervals of trinexapac‐ethyl (TE; 14 days, 7 days, or not applied) on anthracnose severity and seedhead production of annual bluegrass mowed to a height of 0.125 inch from 2005 to 2007. Growth regulators did not enhance anthracnose, but occasionally and inconsistently reduced disease severity. Mefluidide had little effect on anthracnose, but ethephon reduced disease 3 to 22% compared to non‐EP‐treated turf. Trinexapac‐ethyl applied every 7 or 14 days reduced anthracnose 4 to 29% and 4 to 16% compared to non‐TE‐treated turf, respectively. Ethephon reduced seedhead cover 12 to 47%, while ME suppressed seedhead cover 12 to 15%. Trinexapac‐ethyl‐treated turf retained seedheads for longer periods than non‐TE‐treated turf, especially when applied every 7 days. Few meaningful interactions occurred in anthracnose or seedhead cover between TE and ME or TE and EP. Thus, TE and EP, or ME can be used on annual bluegrass turf to reduce seedheads without intensifying anthracnose, and may occasionally reduce disease severity.

Dollar spot is one of the most common diseases of golf course turfgrass and numerous fungicide applications are often required to provide adequate control. Weather-based disease warning systems have been developed to more accurately time fungicide applications; however, they tend to be ineffective and are not currently in widespread use. The primary objective of this research was to develop a new weather-based disease warning system to more accurately advise fungicide applications to control dollar spot activity across a broad geographic and climactic range. The new dollar spot warning system was developed from data collected at field sites in Madison, WI and Stillwater, OK in 2008 and warning system validation sites were established in Madison, WI, Stillwater, OK, Knoxville, TN, State College, PA, Starkville, MS, and Storrs, CT between 2011 and 2016. A meta-analysis of all site-years was conducted and the most effective warning system for dollar spot development consisted of a five-day moving average of relative humidity and average daily temperature. Using this model the highest effective probability that provided dollar spot control similar to that of a calendar-based program across the numerous sites and years was 20%. Additional analysis found that the 20% spray threshold provided comparable control to the calendar-based program while reducing fungicide usage by up to 30%, though further refinement may be needed as practitioners implement this warning system in a range of environments not tested here. The weather-based dollar spot warning system presented here will likely become an important tool for implementing precision disease management strategies for future turfgrass managers, especially as financial and regulatory pressures increase the need to reduce pesticide usage on golf course turfgrass.