Efficacy of Insecticides Applied to Soybean Seeds for Controlling Lepidoptera Caterpillars

Abstract

The use of high-quality seeds is essential for the crop to express its full potential. The application of seed treatment constitutes a widely spread operation, every year new products are discovered and used for seed treatment, which can provide a protective effect against pests that attack the seeds, as well as physiological effects to favor the growth and initial development of plants, however, little is known about the influence of insecticides on seed germination and the emergence of soybean seedlings. The experiment was carried out in the Seed Quality Analysis Laboratory and in the experimental field of the Agrarian Sciences Faculty of the National University of Asunción-Paraguay. The objective consisted of evaluating the efficacy of chemical insecticides applied to soybean seeds to control lepidopteran caterpillars during the implantation of the crop, and the effect on the germination of seeds in the laboratory and the emergence in the field. Commercial soybean seeds were used and the treatments were the following (in cc of c.p./100 kg seeds): control (without treatment), thiamethoxam (200), cyantraniliprole + thiamethoxam (200), thiamethoxam + lambda-cyhalothrin (200), imidacloprid (400), imidacloprid + thiodicarb (500) and fipronil (200). The variables evaluated were: germination under laboratory conditions, number of larvae presented at 14, 21 and 28 days after emergence, seedling emergence and efficacy of chemical products in the field. The design used in the field was complete block to the random and in laboratory fully randomized, with seven treatments and 4 replications with a total of 28 experimental units for both trials. The data obtained were compared through the analysis of variance using the statistical software SASM-Agri and those variables that presented significant statistical differences between the means of the treatments were compared using the Scott-Knott test at 5% probability, while efficacy was determined by the Abbot formula. The data show that the chemical insecticides did not affect the germination of seeds in the doses tested. The highest percentages of emergence in the field were obtained with the insecticides thiamethoxam, cyantraniliprole + thiamethoxam, imidacloprid and imidacloprid + thiodicarb. At 28 day after seedling emergence the active ingredients cyantraniliprole + thiamethoxam and imidacloprid + thiodicarb achieved the greatest reduction in the lepidoptera population. Seed treatment with the active ingredients used in this study is an effective practice for the control of Spodoptera frugiperda, Spodoptera cosmioides and Agrotis ipsilon caterpillars during the initial stage of soybean cultivation.

The Effect of Different Thiamethoxam Concentrations on Riptortus pedestris Development and Fecundity

“…The selection pressure of insecticides containing thiamethoxam is high in soybean fields in Northern China, which are sprayed two or four times during the flowering stage [10,13]. In addition, thiamethoxam is applied through seed coating in soybean and does not affect seed germination [67]. Thiamethoxam and its main metabolite (clothianidin) exhibited a less notable effect on nontarget piercing-sucking herbivores and the earthworm Eisenia fetida (Oligochaeta: Lumbricidae) [68,69].…”