Leaf Disk Bioassay, 1987

Abstract

Abstract ‘Early Round Dutch’ variety cabbage was direct seeded in single-row beds with 40-inch centers in a Willacy fine sandy loam soil at the Texas Agricultural Experiment Station, Weslaco. Plots measured 55 ft by 2 beds and were bordered by 1 bed of grain sorghum. Treatments were replicated 5 times in a randomized complete block design. Spray applications were applied by tractor-mounted CO2-powered boom calibrated to deliver 20 gal/acre at 60 psl operated at 3 mph, Fully expanded cabbage leaves were randomly collected from each plot 2 h after spray applications, In the laboratory 1-inch-diam disks were cut from the leaves and placed on top of filter paper in 5Va-oz creamer cups with tight fitting lids (holes were punched in the lids to allow for air flow), Ten larvae were placed In each cup, Two bioasiays were run; once with early (second and third) instars and once with late (fourth and fifth) instars. Each treatment was replicated 5 times, Mortality was recorded at 24 h intervals, Larvae were considered dead if they did not exhibit a coordinated response when probed. After 72 h, disks were removed from the cups with early Instar larvae and passed through a Ll-Cor leaf area meter to determine amount of disk remaining, Data were summarized and subjected to ANOVA and DMRT for mean separation, Data for leaf consumption are reported as means and standard deviations.