Golf Course Management

JAN 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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118 GOLF COURSE MANAGEMENT 01.19 Application of seaweed extract failed to reduce annual bluegrass, with or without FeSO 4 in the mix. And applications of FeSO 4 by itself, without any PGRs? In those treatments, the infestation of annual bluegrass was reduced to an average of 21%. However, it should be noted that annual bluegrass infestation also naturally declined in every plot (even the con - trols) to an average of 37%, likely a result of competitive creeping bentgrass in a low-phos - phorus environment. So, the addition of FeSO 4 , by itself, did re- duce populations of annual bluegrass a little bit. Should you consider using FeSO 4 as part of your bentgrass management program? Well … maybe. First, adding FeSO 4 to the aggressive paclobutrazol program did not improve annual bluegrass control. Second, the medium rate of FeSO 4 often provided the highest turfgrass quality — a result of the dark green color. e highest rate of FeSO 4 was too much, and plots were too dark. Before definitive recommenda - tions can be made about the inclusion of FeSO 4 for annual bluegrass control, it probably needs to be examined further, in combination with lower rates of paclobutrazol that fit within label recommendations. Sources: Ervin, E.H., N. Reams, X. Zhang, A. Boyd and S. Askew. 2017. An integrated nu - tritional and chemical approach to Poa annua suppression in creeping bentgrass greens. Crop Science 57:567-572. Beth Guertal, Ph.D., is a professor in the Department of Crop, Soil and Environmental Sciences at Auburn University in Auburn, Ala., and 2019 president of the Crop Science Society of America. She is a 20-year member of GCSAA. Beth Guertal, Ph.D. guertea@auburn.edu Twitter: @AUTurfFert Ironing your Poa annua? (verdure) Suppression of Poa annua in bentgrass put- ting greens is an issue for turfgrass manag- ers, with control often relegated to the use of plant growth regulators. us, any additional management methods that may help with Poa annua suppression are always of interest. ese methods include fertilization practices, such as the use of iron. To explore this idea of in - tegrated annual bluegrass control, researchers at Virginia Tech studied combinations of iron sulfate (FeSO 4 ) and plant growth regulators (PGRs) over a two-year period, applying the treatments to a 25-year old Penneagle creeping bentgrass putting green. Specific treatments were rates of FeSO 4 (which was 19% Fe + 11% sulfur) applied at total rates of 0, 0.25, 0.5 and 1 pound/1,000 square feet (0, 12.2, 24.4 or 48.8 kilograms/ hectare) per year (note that these rates are FeSO 4 , and not Fe), with the FeSO 4 applied biweekly in March-October. Growth regula - tors were: (1) seaweed extract (SWE); (2) pa- clobutrazol, applied at 0.007 pound a.i./1,000 square feet (0.36 kilogram a.i./hectare) in March-June and September-October, and 0.004 pound a.i./1,000 square feet (0.18 ki - logram a.i./hectare) in June-August (note that these rates are much higher than label recom - mendations); or (3) no PGR. e PGRs were also applied biweekly. All materials were ap - plied as foliar sprays and allowed to remain on the foliage for 24 hours, after which, the turfgrass was watered. e nitrogen source was ammonium sulfate applied uniformly every two weeks (March-November) at 0.1 pound nitrogen/1,000 square feet (4.8 kilo - grams/hectare). Collected data included per- cent annual bluegrass infestation, using a grid to count plants in each plot, and turfgrass quality. At the beginning of the study, the green had a natural infestation of about 45% an - nual bluegrass. Over the two years of treat- ment applications, the collected data began to show an interaction between the PGRs and the Fe treatments. Basically, application of paclobutrazol reduced annual bluegrass popu- lations to less than 10%, and this happened no matter how much FeSO 4 was applied. So, adding FeSO 4 provided no additive benefit to the paclobutrazol for annual bluegrass control. Should you consider using FeSO 4 as part of your bentgrass management program? Well … maybe.

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