Effects of Insecticides on Thrips Populations, Peanut Injury, Growth, and Yield, Chickasha, Okla-Homa, 1996

Efficacy of selected insecticides was evaluated for tobacco thrips control and for effects on growth and yield of ‘Okrun’ runner type peanut in Chickasha, OK. Peanut was planted on 36-inch rows on 22 May. A RCB experimental design was used with 4 replicates. Plots were 4 rows wide by 45 ft long. Granular insecticides were applied into the seed furrow at planting with a tractor-mounted John Deere granular applicator. Peanut planted with Orthene in the hopperbox was done last, to avoid planter box contamination. Preweighted amounts of Orthene 75 S were added evenly over the seed, alter-nating one-third seed then one-third chemical, until the boxes were filled. Foliar treatments were applied after plant emergence using a CO2-pressurized backpack sprayer calibrated to deliver 20 gpa at 30 psi through one 8004 E flat-fan nozzle per row. Spray treatments were applied 18 days after planting (9 Jun). Treatments were evaluated by comparing plant stand counts per 1/1000 of an acre and injury ratings on a 0 to 10 scale: 0 = no thrips-injured leaves; 10 = 100% injured leaves and dead plants. In addition, thrips control was evaluated by collecting 5 unopened quadrifoliate leaves per plot on 3 Jun. 13 Jun, 20 Jun, and 27 Jun. Unopened leaves were placed in vials of alcohol and returned to the laboratory where adult and larval thrips were separated and counted under a dissecting microscope. Yields were based on digging, combining, drying, and weighing peanuts from 2 rows of each plot. Data were analyzed using ANOVA and LSD procedures.