As 2024 comes to a close, we’re looking back at the list of outstanding research articles that appeared in Golfdom this year. We want to thank all the authors for working closely with us to bring you the results of their excellent research.
I hope this has been an excellent year for you all, and we wish you all the best in 2025!
By Michelle DaCosta, Eric Watkins and Dominic Petrella
(Photos by: Michell DaCosta)
We evaluated a set of 12 creeping bentgrass cultivars for differences in seedling vigor and establishment in response to low temperatures and variable light intensities.
Exposure of creeping bentgrass seedlings to freezing temperatures temporarily inhibited photosynthesis and growth of some cultivars more than others, with cultivars such as Piranha, Declaration, T1 and Penn A4 showing the highest tolerance to freezing events.
Creeping bentgrass cultivars differ in their overall seedling vigor when grown under lower nutrient availability and at lower temperatures.
Based on replicated field experiments in Minnesota and Norway, using shade cloths to achieve 50 to 90 percent reductions in light intensity increased photochemical efficiency and growth of creeping bentgrass seedlings during low temperatures typical of spring months.
Different creeping bentgrass cultivars did not significantly vary in their overall establishment rate, but synthetic permeable cover decreased the time needed to achieve 50 percent turf coverage during spring establishment.
The green strip on this bermudagrass putting green was treated with fluopyram once in the fall before overseeding. In the untreated areas, there is extensive sting nematode damage. (Photo: John Rowland)
Not all nematodes found in the soil are detrimental. Some feed on soil pests, mineralize nutrients and decompose organic matter.
If you think nematodes are responsible for turf damage, proper sampling is essential to determine the species present and the population sizes.
Tolerance thresholds for plant-parasitic nematodes can vary greatly depending on the species of nematode, turf species and variety, soil type and condition, location and climate.
Cultural practices — particularly adequate irrigation and fertilization — may allow you to manage nematode issues under light to moderate pressure without chemical applications.
Test control products on a small scale first to determine their effectiveness to avoid wasting time and money on larger applications that may not work.
Following final applications in late August, Maxtima and Xzemplar had lower dollar spot severity than Traction on the ‘Crenshaw’ green in September, but all fungicide treatments performed better than the untreated control throughout the course of the study.
On the ‘Pennlinks’ green, Lexicon, Maxtima and Navicon treatments provided excellent dollar spot control throughout the season.
(Fig. 2) Fungicide treatments on a ‘Crenshaw’ creeping bentgrass putting green. Maxtima and Traction’s final applications were made on Aug. 30, and Xzemplar’s final application was made on Aug. 23. Arrows indicate application dates for each fungicide on 14 d (Xzemplar) and 21 d (Maxtima and Traction), respectively.
Fairway Trial
Plots treated with Encartis (3 fl. oz./1000 sq. ft. – 14 days), Encartis (3.5 fl. oz./1000 sq. ft. – 21 days), both Xzemplar rates and program-treated plots had the fewest dollar spot infection centers several weeks after the final application.
Encartis rates and application timing did not significantly affect dollar spot control. However, plots treated more frequently (14 and 21 days) with Encartis at lower rates had fewer dollar spot infection centers than Encartis applied at a higher rate and 28-day intervals.
Different application rates and timing within Xzemplar and Maxtima treatments did not significantly affect dollar spot control during the study.
Daconil Ultrex and Secure, both individually and combined, provided less residual dollar spot control than other treatments. This is not surprising for contact-protectant fungicides, which are more prone to removal through mowing or environmental degradation than systemic fungicides that get into the plant. Contact fungicides are less prone to resistance development and are important tools for fungicide resistance management.
Irrigating with a green-coverage-based approach reduced irrigation needs compared to an 80 percent ETo replacement approach.
A Mid-Atlantic type Kentucky bluegrass and tall fescue required the least supplemental irrigation.
Turf-type tall fescue maintained acceptable quality with less irrigation than creeping bentgrass.
Researchers at Purdue University evaluated the irrigation requirements of six cool-season turfgrass species and ten cultivars utilizing two distinct irrigation methods: 80 percent evapotranspiration (ETo) replacement and a green cover threshold (GCT) strategy. (Photo: Jada Powlen)
All treatments at North Carolina State University significantly suppressed Pythium root rot based on AUDPC values except for Subdue MAXX. The rotation of Segway with Serata almost completely suppressed the development of Pythium root rot.
In July at Clemson, Serata had comparable control of Pythium root rot disease to Segway. Tank mixing a lower rate of Serata (0.4 fluid ounces) with Fame SC 0.36 fl. oz. provided comparable control to higher rates of Serata or Segway alone.
At Rutgers, AUDPC values on ryegrass rough for all treated plots were significantly lower than those for the untreated check. Plots treated with Banol had lower values than Segway at both rates but were not different from plots treated with Union and Subdue Maxx.
For peak disease on perennial ryegrass in July at Rutgers, Banol (severity of 5.6 percent) was not statistically different from Subdue Maxx with 17.1 percent disease severity.
By Benjamin Pritchard, Devon E. Carroll, Tyler Carr, Gregory Breeden and James T. Brosnan
Table 3
In 2020 and 2021, researchers at the University of Tennessee evaluated imazapic, a herbicide labeled for weed control in pastures, rangeland and non-crop areas, for growth suppression of four hybrid bermudagrasses.
Separate experiments on ‘TifTuf,’ ‘Tifway,’ ‘Tahoma 31’ and ‘Latitude 36’ hybrid bermudagrass.
Normalized differential vegetation index (NDVI) data were collected, and growth suppression was quantified via reductions in dry clipping weight.
Hybrid bermudagrass injury increased with imazapic rate for all cultivars, and peak injury (> 30 percent) following all imazapic treatments occurred within 14 days.
At the lowest imazapic rate of 0.5 ounces per acre (35 g ha–1), the injury was transient, with all hybrid bermudagrass cultivars fully recovered by 28 days.
All rates of imazapic reduced hybrid bermudagrass dry clipping weight for 21 days on all cultivars.
Winter rains and snow melts led to rapid degradation of both propiconazole and chlorothalonil.
The presence of snow did not impact the persistence of either fungicide.
Transfilm slightly increased the persistence of chlorothalonil but not propiconazole.
The research plot at the OJ Noer Turfgrass Research Facility in November 2015. Half the plots were kept covered in snow for the entire winter and half the plots had snow removed for the entire winter. (Photo: Paul Koch)
By Jordan Booth, Dana Sullivan, Shawn Askew, Kevin Kochersberger and David McCall
Spring dead spot (SDS) is a destructive disease that affects bermudagrass and hybrid bermudagrass in the Transition Zone of the United States.
The study aimed to develop SDS incidence maps using digital imagery captured with an unmanned aerial vehicle (UAV) and evaluate the efficacy of targeted, site-specific penthiopyrad treatments guided by these maps.
The results showed that targeted penthiopyrad treatments based on SDS incidence maps had significantly less disease than tebuconazole and the non-treated control in 2016-2017.
Full-coverage penthiopyrad was superior to targeted penthiopyrad and tebuconazole in 2017-2018 for both diseased area (DA) and patch count (PC).
Targeted penthiopyrad using SDS incidence maps required 51 percent fewer fungicides in 2016-2017 and 65 percent less in 2017-2018 compared to full-coverage penthiopyrad.
Our results suggest that targeted, site-specific management of SDS can reduce the amount of fungicide applied and lower costs while still providing acceptable suppression of the disease.
Variables identified as significant predictors of phosphorus, nitrogen and chlorophyll-a concentrations in stormwater ponds. Arrows indicate positive, negative or both positive and negative variable coefficients.
By Charles Nealis
The stepwise regression model identified key predictors for total phosphorus (TP), total nitrogen (TN) and chlorophyll-a concentrations in clear and colored stormwater ponds, refining variables through least squares fitting.
Littoral shelf coverage and grass clippings emerged as significant predictors, with complex relationships between pond type and nutrient concentrations impacting TP, TN and chlorophyll-a levels.
Littoral shelves and submerged vegetation influence nutrient dynamics, with higher plant coverage generally reducing TN and TP concentrations while affecting chlorophyll-a in varying ways.
Residential fertilizer application and management practices such as chemical treatments and aeration were significant factors influencing nutrient levels, with restrictions on fertilizer use effectively reducing TP and TN concentrations.
Surrounding land use, including natural areas and wetlands, contributes to nutrient dynamics and shows complex relationships that sometimes contradict conventional expectations regarding runoff from developed areas.
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