Golf Course Management

AUG 2018

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

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Page 68 of 97

08.18 GOLF COURSE MANAGEMENT 63 is needed — in addition to cultural practices that help minimize the presence of P. annua to begin with. Although P. annua is a global problem in all turfgrass situations, this article will focus on control strategies in non-over - seeded bermudagrass and zoysiagrass. Most pesticides in turf (and almost all her - bicides) are also registered in field crops. e turfgrass industry benefits from this, as many of the basic environmental and toxicology tests required by the U.S. EPA have already been completed by the time these products have reached the turfgrass market. e Weed Science Society of America (both authors are active members) tracks worldwide herbicide resistance. Figures 2 and 3 indicate two very disturbing trends. Figure 2 tracks the increase in cases of unique herbicide resistance. Unique dazomet (Basamid, AMVAC). Everyone would agree this is not a good position for most golf courses. erefore, it is time for ev - eryone (turfgrass managers, industry person- nel, university researchers, distributors, etc.) to get serious about herbicide resistance. Resistance Since no new herbicidal mode of action has been introduced to the turfgrass market in more than 25 years, and no new ones are on the horizon, being best stewards of exist - ing products is the primary way to delay re- sistance while maximizing the usefulness of these products. Contrary to what many think, herbicides do not cause resistance to occur or develop in plants. Resistance follows Darwin's theory of evolution by natural selection, where Global increase in unique resistance cases herbicide resistance is defined as resistance of a particular weed to a specific mode of action. For instance, if 1,000 cases of simazine-resis - tant P. annua exist, that counts as only one unique case of resistance. Figure 3 indicates members of the Poa grass family (Poaceae) ac - count for nearly twice as many cases of resis- tance as any other family of weeds. We believe this is due to wide genetic variation in the Poa family of plants. Many agricultural scientists (including these authors) think herbicide re - sistance is the most worrisome trend in world- wide agriculture. e incidence of resistance in turfgrasses is abundant in many areas of the country. In some areas, herbicide resistance on putting greens is so extensive that the only course of action is to shut down and renovate using Figure 2. Global increase in unique cases of herbicide resistance. Data includes herbicide resistance in all of agriculture including turfgrasses. New cases of herbicide resistance are discovered every year. Illustration by Ian Heap,, 2018 1955 1965 1975 1985 1995 2005 2015 500 450 400 350 300 250 200 150 100 50 0 YEAR No. of unique resistance cases

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