Pyrethroid Insecticides at Standard and Reduced Rates for Management of Sunflower Beetle Larvae, 1996

A grower-established sunflower field (planted on 25 May with a seeding rate of 23,300 per acre) was found to have sufficient SB larvae (5 per plant) to conduct our insecticide evaluations. This site in north-central South Dakota (Ipswich) was used to evaluate 3 pyrethroid insecticides at standard and reduced rates for management of SB larvae. Plots were 25 ft long by 8 rows (36 inch spacing) wide and the study was arranged in a RCBD with 4 replications. Treatment plots were buffered by 2 untreated rows to prevent cross-contamination between plots due to insecticide drift. Pre-application evaluations used whole-plant counts which were carried out on 20 plants per plot. Treatments were applied to plots on 2 Jul at V-8 stage of sunflower physiological development. Applications were made using a CO2-propelled backpack sprayer system equipped with a 6.7 ft long, 4-nozzle (TeeJet 8001 flat fan; spaced 20 inches apart) boom. The system was calibrated to deliver a spray volume of 15 gpa while traveling at 3 mph. Efficacy was evaluated at 7 and 24 DAT using the same counting technique and number of plants sampled as pre-application sampling. Data were analyzed with SAS’s General Linear Models procedure and means were compared using DMRT.