Golf Course Management

MAR 2015

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

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92 GOLF COURSE MANAGEMENT 03.15 ally, aggressive herbicide use after interseeding could shift the competitive balance away from annual bluegrass toward the desired turf. Herbicide use over new seedlings is a compromise between seedling safety and the potential for the target weed to reduce estab - lishment. Given the tremendous potential for annual bluegrass to dominate seedlings of the desired turf, it is likely best to err on the side of applying herbicides early to seedlings. This would be especially true in the fall when cool-season turfgrasses are not under signif - cant stress. Velocity (bispyribac-sodium, Nufarm) is currently the industry standard for post-emer - gence selective annual bluegrass in seedling creeping bentgrass or perennial ryegrass. Te - nacity (mesotrione, Syngenta), has excellent seedling tolerance over Kentucky bluegrass and perennial ryegrass and can control annual bluegrass pre- and post-emergence. The pre- emergence herbicide dithiopyr has the most fexible label for use over new seedings. Our objective was to determine whether summer seeding and post-seeding herbicides will im - prove success of fairway interseeding as mea- sured in composition of annual bluegrass ver- sus desired turf. Our studies began in summer 2011 and are located on the fairways of three golf courses of various maintenance levels in Iowa and Nebraska. Golf courses included Country Club of Lincoln (Neb.), Crooked Creek (Lin - coln, Neb.) and Ames (Iowa) Country Club. Fairways are mixed stands of annual blue - grass as well as perennial ryegrass, Kentucky bluegrass and/or creeping bentgrass. Seed was dropped into seedbeds after solid-tine aerifca - tion. Treatments include seeding dates (June 15, July 15 or Aug. 15), interseeded species (unseeded, creeping bentgrass, perennial rye - grass or Kentucky bluegrass, depending on location), and herbicides (untreated; Velocity [on creeping bentgrass] or Tenacity [on Ken - tucky bluegrass or perennial ryegrass] applied two and four weeks after seeding; dithiopyr applied in early fall and early spring; or Veloc - ity/Tenacity applied after seeding plus the two applications of dithiopyr. Results were variable across these locations since environments ranged from an urban country club (Lincoln) with limited air move - ment to Ames CC, which is relatively wind- swept, to a daily-fee public course with limited shade. The fnal data in May 2014 are most important in this study, taken after three years of treatments. However, fnal annual bluegrass data in Ames was affected by widespread win - terkill in 2013-2014 from extended snow cover in the low area where the experiment was lo - cated. Data from Ames in fall 2013 indicated that overseeding with perennial ryegrass was most effective in reducing annual bluegrass cover, especially when followed with Tenacity applied two and four weeks after seeding. The other two locations did not suffer win - terkill and thus data continued through 2014. Interseeding creeping bentgrass was most ef - fective at reducing annual bluegrass at Lincoln CC, especially when followed with Velocity applied at two and four weeks after seeding. When interseeding Kentucky bluegrass or pe - rennial ryegrass into lower-maintenance fair- ways at Crooked Creek, Tenacity applied two and four weeks after seeding was the domi - nant factor reducing annual bluegrass popu- lations while overseeding species had little ef- fect. Surprisingly, seeding date had little effect on minimizing annual bluegrass regardless of location. Our data reinforce one of our origi - nal hypotheses that herbicide use shortly after germination is critical for minimizing annual bluegrass competition and maximizing estab - lishment, regardless of the species chosen for overseeding. Zac Reicher ( is a professor and Matt Sousek is a research technologist in the department of agronomy and agriculture at the University of Nebraska, Lincoln; David Minner is a professor in the horticulture department at Iowa State University, Ames; and Andrew Hoiberg is now director of research and development at Calcium Products, Ames, Iowa. Interseeding a desired species usually occurs after annual bluegrass is thinned by summer stress. However, the lighter-colored annual bluegrass germinates quickly and usually outcompetes the desired turf if no post-seeding herbicides are used. Photo by Zac Reicher

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