Effects of certain systemic insecticides on growth and yield of soybeans.

Abstract

An experiment was performed at Tallassee, Alabama, to determine if the application of certain systemic insecticides at the rate of 1 lb per acre applied in various ways had significant effects on the soybean plant other than those related to insect control. Disulfoton, phorate, carbofuran, and methomyl were applied as preplant granules, granules as sidedressing, foliar spray at 1st bloom, foliar spray at midbloom, foliar spray at full bloom, and a combination of all these methods. Stand counts revealed that germination was not affected by application of preplant granules. In a series of 3 plant-height measurements, the measurement made after a foliar spray application at midbloom was the only one to show significant differences among treated plots. Plants were taller in plots treated with methomyl and carbofuran than in plots treated with disulfoton or check plots. Data on height of the 1st pod from the ground, number of mature pods per plant, and yield revealed no significant mean differences. However, differences were detected in seed size (weight) because of methods of application. Plants treated with foliar sprays at 1st bloom, foliar sprays at midbloom, or combination treatments produced larger seeds than plants on other plots.