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In terms of the relative importance of weed control issues, golf course superintendents emphasized clean sprig source, to avoid problems of bermudagrass off-type contamination (Table 2). Next in importance, they expressed concern about weeding and invasion from non-play areas, ornamental grasses, and lake margins. Virtually tied for third place in weed control importance were high visibility areas, e.g., clubhouse and areas next to cart paths and spot treatment of goosegrass. By way of background, weeds are the second most reported management problem on Florida golf courses, after insects, based on the 1991/1992 study of the Florida turfgrass industry by Hodges (1994). According to the 1996 Golf Course Superintendents Report, Florida golf course superintendents spend nearly three times as much on herbicides as do superintendents elsewhere, $16,800 per year compared with $6,300 elsewhere in the United States. A well targeted weed research program must prioritize problems based partly on their seriousness, as well as other factors such as the likelihood of making significant improvements, and the amount of work already being done on a particular problem. Sometimes people ask for help on niche grasses and niche weed problems. These problems need attention, and are academically interesting, but a sense of priority is to take care of No. 1, first. For the southern tip of peninsular Florida, we are on the same latitude as no other place in the United States, therefore there may be weed control problems that are unique to our area, and a greater need to understand those unique problems. Therefore, for a widespread weed control problem such as goosegrass, we can "borrow" to some degree the successful research results from neighboring states such as Georgia, but for a weed such as tropical signalgrass (smallflowered Alexandergrass), which is primarily a south Florida problem, we need to devote considerably more effort. The first questionnaire, 12 March 1998, involved 98 turf managers, primarily golf course superintendents, attending the 11th annual South Florida Golf Superintendents Association Turf EXPO, at Fort Lauderdale Research and Education Center. (The group included 15 sports turf managers, who also maintain bermudagrass turf.) Respondents were asked to rank the relative seriousness of various weeds (Table 1) on a 1- to 3 basis, with 1=most serious. They also added any weeds missing from the list of nine choices, ranked the factors contributing to the "seriousness" of a weed problem, and ranked the effectiveness of the top three preemergence herbicides for goosegrass control in bermudagrass turf (data not presented). The second questionnaire, 29 January 2001, involved 55 primarily golf course superintendents, attending the Everglades Golf Course Superintendents Association meeting in Naples, Florida. Superintendents were asked to rank the relative seriousness of various weeds on a 1- to 12 basis, with 1=most serious (Table 1). They also ranked the importance of weed control issues (Table 2), and added any weeds missing from the list of 12 choices. Unfortunately, green kyllinga, which was on the first questionnaire, was not on the second questionnaire. The third and fourth questionnaires were identical to the second, with the addition of green kyllinga and pigweed. They were completed, respectively at the 13th South Florida EXPO, at UF-Fort Lauderdale, 22 March 2001, and at the Treasure Coast Golf Course Superintendents Association, 19 June 2001. To develop a relative seriousness value, rank scores were inverted to fractions, thus 1 was converted to 1, and 2 was converted to 0.5, and 3 was converted to 0.333. Inverted rank scores were converted to relative values, based on the sum of inverted ranks for each observer. For example, if someone only ranked two weeds, 1 and 2, then the relative rank for weed 1 would be 1/1.5 or 0.667, and the relative rank for weed 2 would be 2/1.5 or 0.333. This way, each individual's rankings had the same value, and the converted scores gave a diminishing credit to a weed, depending on how low it was on the list of people's seriousness ranking. The sum of relative inverted rank scores was found for each weed and each weed control issue, and these were converted to an overall percentage of the sum of all accumulated units scores for all weeds, for each group of participants. For purposes of presentation here, unweighted averages were used, i.e., each location counted equally even though there number of respondents varied by location. Goosegrass was the most serious weed in golf turf, and was rated #1 by three out of four groups. This is consistent with the 1996 Golf Course Superintendents Report, in which goosegrass was also listed as the highest problem intensity weed in the Florida region. Following goosegrass, no weed was consistently in second place. The variation among groups of participants may reflect different regional weed control seriousness, or it may reflect seasonal factors. Sedges were not asked about at the Everglades GCSA meeting in 2001, but there were 20 write-in votes for sedges, mostly not specific, "sedge," although three respondents indicated that kyllinga was serious. It was surprising that crowfootgrass exceeded Poa annua in seriousness, in the questionnaire taken at the Everglades GCSA, in the coolest month of the year, when Poa annua would normally be at its most prolific condition. Nevertheless, a show of hands at the 2001 meeting revealed that approximately 75% of the superintendents had not overseeded. At the same meeting, there were write-in votes for pigweeds (including five for redroot pigweed, almost certainly a misidentification), and five for doveweed. Old World diamondflower is frequently misidentified as doveweed, so it is possible that this too was a misidentification. When pigweed was added to the questionnaire for the third and fourth groups of participants, it rated in seriousness only 1% overall. Even after green kyllinga was restored to the questionnaires, there were numerous write-in votes were for nutsedges (yellow and purple). Other write-in votes by single individuals were for speedwell, sprangletop, virginia buttonweed, creeping beggarweed, volunteer rye, and Muhly grass in Spartina (an example of the problems of maintaining native grass beds). There were a few write-in votes for problems of bermudagrass contamination in seashore paspalum. Seriousness, weed research priorities, and current work Goosegrass is easily prevented on south Florida golf courses by several preemergence herbicides. Unfortunately, the cost of season-long protection is considered too great for some golf courses to be on a regular program, thus they get into a pattern of spot treatment, which should be the method of last resort. (See Philip Busey, "Goosegrass and golf don't mix," Golf Course Management 67(9): September 1999, pages 63-66.) Research should focus on improving the timing of preemergence application, and the need for investment in consistent treatments, to reduce the goosegrass seed bank. Torpedograss is a potential problem everywhere on the golf course, including mitigated wetlands and native grass plantings. While Drive 75DF lessens torpedograss, based on my observations it requires more than two years of treatments to remove it entirely. (See Philip Busey, "Torpedograss control," Florida Green: Summer 2001, in press.) A complete program of torpedograss removal must address the problem along lake margins and wetland areas. Based on my research, tropical signalgrass can be controlled in bermudagrass turf with two to four postemergence applications of MSMA, but the problem is often allowed to get out of hand because of misidentification, and failure to follow through with multiple treatments. (See Philip Busey, "Tropical signalgrass spreads easily and is tough to eradicate," Florida Turf Digest 17(3):May/June 2000, pages 14, 16-18). One hypothesis has been proposed that the increased reliance on preemergence herbicides for goosegrass control has left the golf course vulnerable to seedling germination of tropical signalgrass. Companion work on sod farms shows that tropical signalgrass is difficult to prevent with existing preemergence herbicides. (See Philip Busey, "Ask the Expert: Regarding Tropical Signalgrass," Turf News 25(4): July/August 2001, pages 70-72). Among other serious weeds, the crabgrasses are closely related to tropical signalgrass, but much easier to control. Areas with a crabgrass problem have probably not had MSMA applied on a regular basis. Among the sedges, large areas of green kyllinga often infest the fairways. This is primarily a problem in late fall and early winter, as the kyllinga seems to fade out between March and April. Only Manage, Image, and MSMA+Sencor are highly effective against kyllinga, and Manage is the least likely to injure the bermudagrass. (See Philip Busey, "Optimum herbicide strategy for managing mixed weed populations in the southern U.S., International Turfgrass Society Research Journal 7: 2001, pages 1001-1004). Poa annua is the main weed of perennial ryegrass overseeded into bermudagrass turf. It is hard to control because of the risk of injuring both the perennial ryegrass and the underlying bermudagrass turf. While this is a niche problem in south Florida, for the minority of superintendents who overseed, it deserves more careful research. For the broadleaf weeds, which are generally not serious in golf and sports turf, there are many excellent phenoxy broadleaf mixtures, although there is some uncertainty about which to use on difficult tap-rooted species such as pigweed. Manor herbicide and possibly Lontrel are the best backups for very difficult broadleaf weeds. Other mixtures for the future may include carfentrazone. References 1. Anonymous. 1996. 1996 Golf Course Superintendents Report, Golf Course Superintendents Association of America, Lawrence, Kansas. 2. Hodges, A. W., J. J. Haydu, P. J. van Blokland, and A. P. Bell. 1994. Contribution of the turfgrass industry to Florida's economy, 1991/92: A value added approach. University of Florida IFAS Economics Report ER 94-1.
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Table 1. Relative seriousness for four participant groups, unweighted seriousness, and rank, of 14 weeds (species or genera) in golf and sports turf in south Florida, 1998-2001.
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Table 2. Relative importance for three participant groups, unweighted importance, and rank, of seven weed control issues for golf and sports turf managers in south Florida, 1998-2001.
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