Chemical Control of Cyclocephala Spp. in Tall Fescue.

Field experiments were conducted at the Texas Tech Turfgrass Research Farm, Lubbock, TX in 2008 to examine the effect of several insecticides for the control of Cyclocephala spp. Studies were located on established infestations of Cyclocephala spp. present in a mature tall fescue stand grown on a Brownfield Sandy Clay Loam (loamy, mixed, superactive, thermic Arsenic Aridic Paleustalfs). Plots measured 1.5 x 3.0 m and were arranged in a randomized complete block design with four replications of treatments. Treatments were applied using a CO₂ backpack sprayer equipped with XR8004VS nozzle tips and calibrated to deliver 374 L/ha at 221 kPa. Treatments were made on 5/9/2008 and consisted of chlorantraniliprole (0.12 or 0.18 kg ai/ha), imidacloprid (two separate manufacturers)(0.35 kg ai/ha), and clothianidin (0.22 or 0.34 kg ai/ha). Plots were irrigated with 0.6 cm of water immediately after insecticide application. Visual estimates of percent tall fescue phytotoxicity were taken 1, 2, and 3 weeks after initial treatment (WAIT). On September 21, 2008 (20 WAIT) a 0.5 m² area was randomly selected within each plot and excavated to a depth of 0.5 m. Cyclocephala spp. were counted in each 0.5 m³ sample and converted to percent control upon comparison to untreated check plots. Untreated check plots contained 15 Cyclocephala spp. in a 0.5 m³ area. Data were subjected to analysis of variance (ANOVA) and means were separated using Fisher’s Protected LSD at the 0.05 significance level. No tall fescue phytotoxicity was recorded throughout the duration of the trial. Chlorantraniliprole treatments exhibited 100% control regardless of application rate 20 WAIT. Control with imidacloprid treatments ranged from 88 to 91% 20 WAIT. Clothianidin at 0.22 kg ai/ha exhibited 88% control while the higher rate (0.34 kg ai/ha) provided complete control 20 WAIT.