Golf Course Management

MAR 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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30 GOLF COURSE MANAGEMENT 03.19 Screening for natural weed suppression in fine fescues Plants interact with each other above ground (competing for light) and below ground (competing for water and nutrients). A specific case of a negative plant-plant in - teraction is called allelopathy, which occurs when a plant produces and releases into the environment herbicidal compounds that harm neighboring plants through various modes of action. A good example is the case of the bottlebrush plant (Myrtaceae species), which is known for releasing a herbicidal compound called leptospermone, an allelochemical that "bleaches" nearby susceptible plants. Research on leptospermone led to the creation of me - sotrione, the active ingredient in products like Tenacity, and other commercial "bleaching" herbicides. Studying allelopathy can be help - ful for designing new herbicides, but it also has broader implications in plant breeding. Fine fescues have been suspected of hav - ing natural weed-suppressive abilities. Previ- ous work from Cornell University identified a chemical compound, L-m-tyrosine, as a potential allelochemical responsible for the weed suppression observed in field experi - ments. is concept is particularly interest- ing from a breeding perspective, because natural weed suppression offers the potential of breeding for turfgrasses that require fewer pesticide applications. e University of Min - nesota Turfgrass Science team has been ac- tively involved with breeding and evaluating fine fescues, largely because fine fescues have lower maintenance requirements than other cool-season turfgrasses adapted to the region. We began evaluating fine fescues for natural weed suppression in 2014, which has steered our current efforts toward screening for crab - grass suppression. Crabgrass (Digitaria species) is a problem - atic summer annual grassy weed across much of the United States, making it a good candi - date for screening fine fescues for weed sup- pression. Fine fescues were screened for weed suppression in plots with consistent crabgrass populations in fields at the University of Min - nesota Turfgrass Research Outreach and Ed- ucation center in St. Paul, Minn., and at the William H. Daniel Turfgrass Research and Diagnostic Center in West Lafayette, Ind. In our initial field experiment, we tested six ac - cessions and one cultivar for three fine fescue species: hard fescue (Festuca brevipila), Chew - ings fescue (Festuca rubra subspecies fallax), and strong creeping red fescue (Festuca rubra subspecies rubra). We planted the fine fescues as plugs in the field in Minnesota and Indiana in April 2016 in order to evaluate the effect of fine fescues on natural crabgrass populations. After two years of study in field condi - tions, we observed several trends in crabgrass suppression. ere were significant differences in overall crabgrass biomass reduction and the amount of seedheads produced, with consis - tent trends across the Minnesota and Indiana crabgrass populations. In the spring of 2018, we also observed differences in crabgrass emergence in the Minnesota field location. To verify the observations made in the field experiment and to better understand how re - source competition can affect weed suppres- sion, we conducted a separate experiment in a controlled-environment growth chamber to test fine fescues from the field that had shown (turf) Jon M. Trappe, Ph.D. (jtrappe@umn.edu) Dominic Petrella, Ph.D. Florence Sessoms, Ph.D. Eric Watkins, Ph.D. As seen in this field experiment, some fine fescues appear to be able to inhibit crabgrass germination. Photo by Jon Trappe both high and low levels of crabgrass suppres- sion. Similar trends in the reduction of crab- grass biomass, seedhead production, and tiller and leaf number in the controlled environ - ment verified our previous field observations. We also conducted further research under lab conditions to confirm that the suspected al - lelochemical L-m-tyrosine negatively affected crabgrass, potentially explaining field and growth chamber observations. We found that crabgrass suppression varies within and across fine fescue species. Chew - ings fescues and strong creeping red fescues tended to suppress crabgrass more than hard fescues. ese methods and their future re - sults will be helpful in identifying genotypes with higher suppressive/allelopathic ability, which will be used to breed fine fescues that require fewer pesticides. In our future re - search, we will attempt to determine whether a single allelochemical is responsible for crab - grass suppression, screening for weed suppres- sive genotypes against other problematic weed species, and seeking a better understanding of the effect of resource (especially nitrogen and phosphate) competition for weed suppression by fine fescues. A more detailed report of this research will be submitted for publication in a peer-reviewed journal in spring 2019. is research was funded by USDA-NIFA through the Specialty Crop Research Initiative. Jon M. Trappe and Dominic Petrella are postdoctoral asso- ciates, Florence Sessoms is a research scientist, and Eric Watkins is a professor of turfgrass breeding and genetics at the University of Minnesota Twin Cities in St. Paul, Minn.

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