Golf Course Management

MAY 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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Page 73 of 141

70 GOLF COURSE MANAGEMENT 05.19 % disease on a treated Poa annua green Treatments Pounds/1,000 square feet Kilograms/hectare % disease cover (0%-100%) Nitrogen rate † 0.10 4.9 19.1 a‡ 0.20 9.8 29.0 b Phosphorus rate 0.0 0.0 24.4 ns 0.025 1.22 23.7 ns Potassium rate 0.00 0.0 27.2 b 0.10 4.9 20.9 a † Nitrogen, phosphorus and potassium were applied monthly at the given rates beginning in September 2017. ‡ Means in the same column followed by the same letter are not significantly different. Table 1. Effects of treatments on percent disease on an annual bluegrass putting green on Feb. 22, 2018, in Corvallis, Ore. and potassium were not significant. Find- ings suggest that applications of nitrogen and potassium in fall through spring at 0.10 pound/1,000 square feet each can mitigate Microdochium patch activity (Table 1). Clint Mattox ( is a graduate student, Alec Kowalewski is an associate professor, and Brian McDonald is a senior faculty research assistant in the Department of Horticulture at Oregon State University, Corvallis, Ore. (report) Investigating the impacts of thatch and microbial degradation on white grub control with imidacloprid Andrew Huling Ben McGraw, Ph.D. Neonicotinoids, particularly products containing the active ingredient imidaclo - prid, have been relied upon heavily by turf- grass managers over the last three decades to control white grubs. Imidacloprid's relatively long half-life in soil and acropetal movement through the xylem allow turfgrass managers to control white grubs preventively, rather than waiting until the root-feeding larvae — or possibly even turfgrass damage — is appar - ent. Compared with older broad-spectrum contact insecticides that provide only mod - erate control, imidacloprid can provide high levels of control with a single application per growing season. However, recent reports from some turf managers in the northeastern United States have indicated that imidacloprid has failed to provide adequate suppression of grubs in areas where they have applied the active ingredient on an annual basis for more than 10 years. Other similarities in reports include greater grub densities in the rough than in adjacent fairways. Although many factors may affect insecticide performance, our studies focused on whether imidacloprid efficacy was affected by thatch or whether soil microbes were re - sponsible for prematurely degrading the active ingredient. By using preventive insecticide applications, superintendents can control white grubs before they can damage turf roots. Besides killing the turf, the grub damage allows small mammals like skunks and raccoons to cause further turf damage in their attempts to find the insects. This photo shows damage from both the grubs and the mammals that are their preda - tors. Photos by Ben McGraw

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