Evaluation of Bt-Pyrethroid Mixtures for Control Of Heliothis Spp., 1988

Abstract

Abstract Efficacies of 4 treatment strategies involving an oil flowable formulation of Bacillus thuringiensis alone and in combination with Ammo were compared with efficacies of Karate and Ammo for control of Heliothis spp. larvae at the Texas Agricultural Experiment Station Research Farm at College Station. Cotton was planted 6 Apr on rows spaced 40 inches apart. A randomized complete block design with 4 replications was used with plots 8 rows × 75 ft long. All rows were sprayed with a self-propelled, high clearance sprayer calibrated to deliver 8 gal/acre through 2 TX-6 hollow cone nozzles/row at 40 psi. Enhancement adjuvant (50 ml/gal) and Bond® spreader/ sticker (5 ml/gal) were added to all spray mixes, except Karate and Karate + Ovasyn, prior to application. Treatments were applied 8 Jul, 15 Jul, 20 Jul, and 26 Jul. Plant damage, insect abundance, and lint yields were assessed from randomly selected locations from the inner 6 rows of each plot. Egg and larval densities and terminal damage were determined once within all plots prior to the first insecticide treatment. Measures of insect damage to fruit were made by examining 50 randomly selected 1/3-grown or larger squares and 50 soft bolls from each plot on the day of, or the day before, insecticide application. Bolls were counted on 2 randomly selected, 6.5 ft sections of row/plot on 8 Aug. Cotton yields were determined by hand harvesting 2 randomly selected, 13 ft sections of row/plot.