Evaluation of Insecticides for Suppression of Sorghum Midge on Sorghum,1993

Abstract

Abstract Two organophosphates, 4 pyrethroids, and corn oil were evaluated for sorghum midge control at the Texas Agricultural Experiment Station Research Farm near College Station, TX. Seed of 6 sorghum hybrids of different maturity rates were mixed together and planted 27 Apr on rows spaced 96.5 cm apart. Mixtures of hybrids of different maturity were used to simulate sorghum with non-uniform flowering as often occurs in fields of sorghum. Insecticide treatments were compared in 8-row X 6.1-m-long plots arranged in a RCB design with 4 replications. Insecticides were applied by using a CO2-pressurized backpack sprayer, through TX-3 hollow cone nozzles at 2.5 kg/cm2, producing a finished spray volume of 62.9 liters/ha. Corn oil was applied using a controlled droplet applicator j with a size 20 orifice plate at 1.4 kg/cm2, giving a volume of 22.5 liters/ha. Conventional treatments were made on 29 Jun and 3 and 7 Jul. Daily treatments ) of Lorsban and corn oil were made from 29 Jun through 9 Jul. Data from plots where maximum sorghum midge control was achieved by using Lorsban daily through the flowering period were compared with that from untreated plots and plots where treatments were applied at conventional intervals of time. Corn oil was applied daily to determine the maximum control achievable by using this oil. Data on kernel loss and grain yield were collected from the mid-dle 2 rows of each plot. Ten sorghum panicles were randomly selected before each insecticide application, enclosed in clear plastic bags, cut, and taken to the laboratory where adult sorghum midges were counted. Twenty panicles per plot were visually rated for damage on a scale of 1-9, where 1 = 0-10% and 9 = 81-90% kernel loss. Panicles were hand harvested from 2, 2.7-m sections of row per plot and mechanically threshed. Data were analyzed statis-tically by using ANOVA and LSD.