Golf Course Management


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09.16 GOLF COURSE MANAGEMENT 93 CUTTING EDGE Teresa Carson Freezing tolerance of creeping bentgrass cultivars Creeping bentgrass (Agrostis stolonifera) is the most popular choice for putting greens in the northern U.S. because it furnishes a high-quality putting surface while also offer - ing high freezing tolerance. Recent breeding efforts have not focused on freezing tolerance, so some newer cultivars may lack the ability to survive extremely low temperatures. In this experiment, we evaluated the freezing toler - ance of five creeping bentgrass cultivars de- veloped over the past six decades (Penncross, L-93, 007, Penn A-4 and T-1). Individual cultivars were seeded into 72 cell flats and al - lowed to develop in the greenhouse before the freezing treatment. Plants were acclimated for two weeks at 37 F (3 C) in a growth cham - ber, and then, using a programmable freezer, were subjected to 10 different freezing tem - peratures ranging from 14 F to -18 F (-10 C to -28 C). After freezing, plants were returned to the growth chamber at 37 F for 48 hours to thaw before being returned to the greenhouse. Whole-plant survival and the lethal tempera - ture for death of 50% of the population (LT 50 ) were determined for each cultivar. Results showed significant differences in freezing tol - erance among the cultivars in this trial. Bent- grass cultivars with the highest level of freez- ing tolerance were T-1 and Penncross, with LT 50 values of 2.24 F and 2.36 F (-16.53 C and -16.47 C), respectively. Cultivars with the lowest level of freezing tolerance were Penn A-4, 007 and L-93, with LT 50 values ranging from 3.32 F to 4.04 F (-15.93 C to -15.53 C). — Matthew Cavanaugh, Samuel Bauer (sjbauer@, Garett Carl Heineck, Andrew Hollman, Eric Watkins, Ph.D., and Brian Horgan, Ph.D., Uni - versity of Minnesota, St. Paul Nematode control with ultrasound waves Plant-parasitic nematodes such as sting (Belonolaimus longicaudatus), sheath (Hemi - cycliop ra species) and ring (Mesocriconema species) nematodes can damage turfgrasses in sandy, well-drained soils. Management with soil fumigants or nematicides are often the only practical options to reduce nematode populations below damage thresholds. Lab - oratory, greenhouse and field trials to deter- mine how ultrasound waves (20 kHz) affect soil nematode populations were conducted during 2009 and 2010 at the University of Georgia's Tifton campus on TifEagle bermu - dagrasses (Cynodon dactylon × C. transvaalen- sis). In preliminary lab testing, all sting nem- atodes that were placed in 15-ml glass vials filled with water and subjected to 10 seconds of ultrasound survived, but all died when ex- posed to 30 seconds of ultrasound. In initial trials conducted on samples harvested from a TifEagle green, 60 seconds of exposure to ul - trasound resulted in an 89% decrease in the naturally occurring sting nematode popula - tions in the soil, but the 30-second treatment had no effect. In further greenhouse testing on TifEagle grown in steam-sterilized soil, sting nematode populations were reduced by 80% in containers that were inoculated and exposed to three minutes of ultrasound weekly for six weeks compared with the un - treated control. Finally, sting nematode pop- ulations in field plots on a TifEagle green were statistically unchanged after 24 days in the control and 1.5-minute ultrasound treat - ments, but were reduced 76% by three min- utes of ultrasound and 87% by treatment with Nemacur. Further research on the ef - fects of different ultrasound wavelengths and methodologies on plant-parasitic nematodes in soil is warranted. — Brian M. Schwartz, Ph.D. (, and Wayne W. Hanna, Ph.D., University of Georgia, Tifton; and Patricia Timper, Ph.D., USDA-ARS, Tifton, Ga. Teresa Carson ( is GCM's science editor. Photo by Matthew Cavanaugh Photo by Brian Schwartz

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