Research Updates from Virginia Tech continued
Can PGRs Control Goosegrass and Crabgrass in Creeping Bentgrass Putting Greens? Virginia Tech Researchers: John M. Peppers, Doctorate Student, and Shawn D. Askew, Ph.D, Professor, Turfgrass Weed Science, Department of Plant Pathology, Physiology, and Weed Science
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oosegrass (Eleusine indica) and smooth crabgrass (Digitaria ischaemum) can be problematic weeds in creeping bentgrass (Agrostis stolonifera) putting greens. These weeds are problematic because they primarily grow during the summer months when creeping bentgrass is growing less vigorously. There is also a lack of selective herbicide options available to control these weeds on creeping bentgrass putting greens. Preliminary research at Auburn University indicated that the use of certain plant growth regulators (PGRs) could prevent establishment of goosegrass in creeping bentgrass putting greens (Figure 1).
OUR RESEARCH
Greenhouse trials were conducted in fall 2021 in Blacksburg, VA to evaluate the effects of PGRs on goosegrass and smooth crabgrass growth. Goosegrass and smooth crabgrass were seeded in pots containing a 1:1 native soil to sand mixture in order to simulate a putting green. Four PGRs were evaluated in this study: flurprimidol (24 fl oz/a), paclobutrazol (16 fl oz/a), trinexapacethyl (6 fl oz/a), and prohexadione-calcium (8 oz/a). Treatments were applied as either one application before weed germination or once before germination and two more applications made biweekly to simulate routine PGR use. This trial included six reps and was repeated in time. Data were plant height, plant counts, above ground plant biomass, and root biomass. All data were subjected to ANOVA using SAS 9.2.
RESEARCH RESULTS
At the conclusion of the trial, flurprimidol and paclobutrazol significantly reduced height of goosegrass and smooth crabgrass when applied either PRE-only or PRE + POST. Trinexapac-ethyl and prohexadione-calcium did not reduce height of either goosegrass or smooth crabgrass. Although no PGR statistically reduced the number of goosegrass plants that germinated in this trial, flurprimidol and paclobutrazol significantly reduced the total number of smooth crabgrass plants that germinated. Neither trinexapac-ethyl nor prohexadione-calcium reduced germination in either species. Additionally, flurprimidol and paclobutrazol reduced goosegrass and smooth crabgrass above-ground biomass while trinexapac-ethyl and prohexadione-calcium did not reduce the above-ground biomass of either species. Flurprimidol and paclobutrazol both significantly reduced the total root biomass of both species while trinexapac-ethyl and prohexadione-calcium did not (Figures 2 and 3). Results from this trial indicate that flurprimidol and paclobutrazol can reduce the competitive ability of goosegrass and smooth crabgrass while the same was not true for trinexapac-ethyl and prohexadione-calcium. Further research is needed to determine if utilizing flurprimidol and paclobutrazol programs throughout the summer can prevent goosegrass and smooth crabgrass establishment in creeping bentgrass putting greens.
FIGURE 1. A creeping bentgrass putting green treated with a trinexapacethyl program (top) compared to a creeping bentgrass putting green treated with a flurprimidol program (bottom). The plot treated with a trinexapac-ethyl program was heavily infested with goosegrass while flurprimidol substantially reduced goosegrass populations.
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FIGURE 2. Effects of PGR on above-ground and below-ground goosegrass plant material. Treatments are as follows from left to right: Nontreated control, flurprimidol PRE-only, flurprimidol PRE + POST, paclobutrazol PRE-only, paclobutrazol PRE + POST, trinexapac-ethyl PRE-only, trinexapac-ethyl PRE + POST, prohexadione-calcium PRE-only, prohexadione PRE + POST. FIGURE 3. Effects of PGR on above-ground and below-ground smooth crabgrass plant material. Treatments are as follows from left to right: Nontreated control, flurprimidol PRE-only, flurprimidol PRE + POST, paclobutrazol PRE-only, paclobutrazol PRE + POST, trinexapac-ethyl PRE-only, trinexapac-ethyl PRE + POST, prohexadione-calcium PRE-only, prohexadione PRE + POST.
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34 | VIRGINIA TURFGRASS JOURNAL January/February 2022
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