Bioatividade do pó de piper nigrum L. sobre Alphitobius diaperinus (panzer) (coleoptera: tenebrionidae) em sementes de amendoim (arachis hypogaea L.) BR1.

Abstract

Pest insects are among the main problems related to the loss of stored grain. The study of botanical insecticides has increased with the demand for products not harmful to the environment and to humans. Among these products, Piper nigrum (black pepper) has been studied due to its insecticidal properties and action on pest insects. This study aimed to evaluate plant bio-insecticides effects on Alphitobius diaperinus (PANZER) control. Bioassays were carried out at Embrapa Cotton, to evaluate the control efficiency and the repellency of P. nigrum on A. diaperinus in peanut seeds cultivar BR1. To perform the first bioassay, peanut seeds cultivar BR1 were used, treated with P. nigrum powder and packed in plastic recipients (7.0 cm diameter x 4.8 cm high). The control efficiency test (E%) was accomplished using 40 adult insects. Four evaluations were performed at intervals of 7 days and the analyzed variables were the number of dead insects and injured seeds. The treatments consisted of five concentrations of black pepper powder (1, 2, 3, 4 and 5%) and a control. For control efficiency analysis it was used the Sun-Shepard's method. Polynomial regression analysis was also performed for the values of efficiency and number of injured seeds. In the second bioassay Arenas were used for repellency test with capacity to accommodate six recipientes (30 g) with treated and untreated peanut seeds (2x2). The repellency test was conducted using 30 adult insects, unsexed, after 24 hours of starvation. The evaluation of the bioassay was performed using each concentration of the mixed of powder and peanut seeds and compared to untreated seeds. The number of insects in treated and untreated seeds was assessed 24 hours after the release of insects in the arenas. The repellency index was calculated by the formula IR = 2G / (G + P), G =% of insects in treated and P =% of insects in the control seeds. IR values range from 0 to 2, indicating: IR = 1, neutral product; IR> 1, attractive product and IR <1, repellent product. According to the results, we concluded that black pepper powder was not efficient on A. diaperinus control, with maximum value of 29.7%, however, affected A. diaperinus capacity of feeding reducing consequently it capacity of causing peanut seeds injury. In all evaluated powder concentrations, pepper powder presented repellent action on A. diaperinus.