Efficacy of Several Formulations of Chlorpyrifos Against Annual Bluegrass Weevils, Golf Course Fairway, 1995

Three formulations of chlorpyrifos (Dursban Pro, Dursban Turf, and Empire 20) were tested for efficacy against annual bluegrass weevil larvae on a golf course fairway in Scarhorough, New York. The fairway consisted of 60% creeping bentgrass, 30% annual bluegrass, 10% perennial ryegrass, and was mowed at ca. 0.8 inches. Treatment plots were 7 ft by 7 ft, replicated 5 times, arranged in a RCB. All applications were made between 7:15 and 9:00 AM on 17 Apr 95. Liquid formulations were applied by hand with a watering can, 3 liters per plot. Conditions at the time of application were as follows: air temp. 48°F, light overcast following a light rain overnight, calm; forsythia just past peak blossom; soil temp. (2 inch), 49°F; soil type, silty loam; soil pH 6.5; water pH, 7.2; thatch 0.6 inch thick with moderate density. The trial was irrigated with 0.1 inch water 30 min after application. Product efficacy was evaluated on 5 June (42 DAT) by inspecting 12 cores (2.1 inch diam) from near the center of each plot, and recording the number of small (lst, 2nd, or 3rd instar), medium (4th instar), and large (5th instar) larvae, pupae, and adults. At the time of sampling, the population was: 28% small larvae, 24% medium larvae, 48% large larvae. Each observation consisted of 3 cores, and there were 4 observations per plot.