Bioatividade do óleo de nim sobre Tribolium castaneum em Alphitobius diaperinus (Coleoptera: Tenebrionidae) em sementes de amendoim armazenado.

Abstract

This work was developed with the aim of evaluating the oil bioactivity of neem seed on the insect pests of stored seeds, Tribolium castaneum e Alphitobius diaperinus. To carry out the bioassays, peanut seeds of the BRS Havana cultivar were treated with neem oil and kept on trays during 24 hours period. Fifty grams of seeds were put in plastic recipients and infested with insects in the adult phase. In the T castaneum bioassay the effect of neem oil concentration of 0.0,0.5,1.0, 1.5 and 2.0% (mass/volume) on 10 not sexed insects maintained in recipients measuring 6.0 cm height and 9.0 cm diameter was avaluated. For A diaperinus the neem oil concentrations of 0.0, 1.0, 2.0, 3.0 and 4.0% (mass/volume) were tested on 20 not sexed insects maintained in recipients measuring 8.0 cm height and 11.0 cm diameter. Both bioassays were designed with five treatments and four replications. The analyzed variables were mortality, offspring number (larva, pupa end adults) and the number of punched seeds, evaluated in four stored periods (30, 60, 90 and 120 days). For data analysis, nonparametric tests were used. Friedman test (P<0.05) was used for variance analysis test and Student Newman Keuls (P<0.05) for means comparison. The neem oil efficiency was evaluated by Abbott method and the punched seeds percentage and the offspring number fluctuations were represented in graphics. In the four evaluated periods T. castaneum obtained mean values of mortality not higher than 37.5%, showing low product efficiency on the adult insect mortality. The biology was enlarged due to T. castaneum feeding on treated neem seed. In all studied period, the number of punched seeds in the control was inferior to each one of the oil concentrations and the most efficient concentrations were of 1.0, 1.5 and 2.0%. The effect of the neem on the insect's biological development, the adult's reproduction, the increase of the larval development phases and on the reduction of pupae and offspring adults* number, during all the stored period, was also observed. For A. diaperinus, the product efficiency on the insect mortality from 90 days of storing, with efficiency varying from 26,01 to 97,50%, was detected. The most efficiency neem concentrations were of 3.0 and 4.0% and the insect mortality was possibly attributed to alimentary deterrence. According to the offspring number, the neem oil made impossible larvae metamorphose, not allowing that the A. diaperinus life history was completed. The control differed statistically of the neem oil treatments to punched seeds number in all studied periods, verifying 100% of damage in the control, except to 30 days period, with approximately 80%. In the oil treatments those percentages varied from 2.7 to 12.9%. Through the offspring number it was verified that neem oil affected all the development phases of A. diaperinus, promoting protection to peanut seeds in all periods evaluated.