Golf Course Management

MAR 2017

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 92 of 125

03.17 GOLF COURSE MANAGEMENT 75 Poa annua removal Annual bluegrass (Poa annua) is believed to be the preferred host plant of annual blue - grass weevil (5), but the pest can also develop in and damage creeping bentgrass (Agrostis sto - lonifera), even in mixed stands where P. annua is not limiting. Because creeping bentgrass is more tolerant and requires greater larval den - sities before damage becomes visible (8), pro- moting creeping bentgrass in mixed stands should help reduce damage and the need for insecticide applications. However, only 54% of respondents indicated they had tried to re - duce the amount of P. annua on the course in order to lessen annual bluegrass weevil dam - age. Many of the courses, especially older courses in the New York City metropolitan area, have large percentages of P. annua in most playing surfaces. Although regrassing the course to reduce weevil damage may not be a viable strategy for such courses, promot - ing creeping bentgrass over P. annua through selective cultural methods and plant growth regulators may be a practical option. Monitoring practices Superintendents regularly employ scouting techniques to estimate annual bluegrass wee - vil population densities or determine presence. Most respondents (90%) indicated they regu - larly use two or more monitoring techniques, and 80% used three or more. Only 5.1% indi - cated that they do not regularly monitor. Sampling practices can be broken down into two categories: passive (scouting prac - tices that require little manual effort) and ac- tive (monitoring practices that estimate pest density). A low percentage of superintendents reported using only one type of technique. Roughly 9% indicated they use only active means to determine population density, and a similar number (8%) indicated they use only passive monitoring techniques (plant phenol - ogy, growing degree days). The remaining 79% of responses indicated the use of both types of monitoring techniques. Passive techniques were favored, even by respondents using multiple means of assessing populations. Syngenta's proprietary monitor - ing system, WeevilTrak, gauges population activity and development across the region from growing degree days and soil and vac - uum samples on courses within a region (the work is carried out by university personnel and consultants). WeevilTrak was used by 72% of respondents and was the most popular means of monitoring annual bluegrass weevil popula - tions. Smaller percentages of respondents used other passive techniques, such as monitoring plant phenology (65%) and calculating grow - ing degree days (45%). More-active means of population assessment included checking mower baskets for adults (61%) and taking soil cores (56%) to observe stages. Other ac - tive measurements that were less popular were the use of soap flushes (40%), traps (for ex - ample, linear pitfall traps) (28%), salt flushes (11%) and vacuum sampling (6%). Information sources and influences Most respondents indicated that they rely on multiple sources including colleagues (82%), salespeople/distributors (80%) and university personnel (78%) for information on annual bluegrass weevil management. Specific "other" responses (9%) included Syngenta's WeevilTrak, consultants and the United States Golf Association's Turf Advi - sory Service. When asked which source has the greatest influence on their decision-making, respon - dents indicated university personnel (43%), followed by colleagues (31%). Colleagues had the greatest influence on management deci - sions in eastern Pennsylvania (50%), Virginia (46%) and the Delaware-Maryland-Virginia region (44%). Salespeople/distributors were the main source of information for 21% of the surveyed superintendents. Their influence was greatest in western peripheral states and regions (56%) and Pennsylvania (24%). A small percentage of responses indicated "con - sultant" (3%) and "self " (3%) as having the greatest influence on management decisions. Consultants were most influential in the deci - sion-making process in New York (10%) and in the northern peripheral states and provinces (8%). These low values likely reflect the rela - tively few turfgrass consulting and scouting services available across the region. C anges to management programs More than half (54%) the surveyed super - intendents indicated they had made changes based on presentations or recommendations made by university researchers and staff. Two- thirds of all responses from New Jersey and New York (including 75% from Long Island) indicated changes were made based on infor - mation from university personnel. The lowest frequency of impact from university personnel was observed in responses collected from Del - aware-Maryland-Virginia (32%) and western Pennsylvania (24%). Most turf managers (94%) described their management changes in the fill-in-the-blank section of the survey. Timing of controls (43%), chemical selection (39%) and chemi - cal rotations (23%) were the predominant responses given. Some respondents (17%) noted they had moved away from pyrethroids or chemical insecticides (in general) based on university research or recommendations. Less common answers dealt with general IPM rec - ommendations, such as learning about scout- ing techniques (8%), reducing sprayed areas (2%), alternative controls (2%), and reducing P. annua populations (1%). Conclusions This survey provides a broad framework for understanding the importance and spread of annual bluegrass weevil as a golf course pest, the spread and severity of insecticide resis - tance, and the need for expanded extension ef- forts to communicate best management prac- tices for the pest. With 90% of respondents indicating damaging densities on their courses and, on average, about one-third of fairways, tees, and greens and collars affected, annual bluegrass weevil clearly is a tremendous prob - lem in the region. Resistance is already wide- spread, with 20% of respondents throughout the region (regionally up to 55%) suspecting or having confirmed resistance, though it is likely many more courses have unknowingly developed or will develop insecticide-resistant populations in the near future. Despite reports of pyrethroid resistance, pyrethroids are still the most widely used in - secticide class for the weevil's management, followed by another adulticide, chlorpyrifos. While "resistant" courses have made signifi - cant changes in insecticide use, particularly greater adoption of larvicides and switch - ing to chlorpyrifos as the primary adulticide, 64% of those courses still used pyrethroids. Greater changes in types of insecticides used are likely being held back by a combination of risk averseness, dominance of preventive approaches by superintendents, and the much lower cost of adulticides compared with the more effective larvicides. However, few classes of insecticides are effective in controlling adult weevils, and the ability for those classes to control pyrethroid-resistant annual bluegrass weevil populations is questionable, as highly pyrethroid-resistant populations already show

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