Extrato metanólico da amêndoa da semente de nim e a mortalidade de ovos e lagartas da traça-do-tomateiro

Abstract

A methanolic extract from neem seed kernels, obtained using the Soxhlet apparatus was used to study the mortality of eggs and larvae of Tuta absoluta (Lepidoptera: Gelechiidae) and to evaluate of the ovicidal effect. Eggs 24 hours after oviposition were counted and sprayed with the extract at the concentrations of 1000, 500, 250, 125 and 62.5 mg L-1. Controls were sprayed with water and methanol. The experiment was conducted in laboratory conditions at 25±2°C; UR 50±10% and 12 h of photophase. Incubation period for all treatments, including controls, was four days on the average. The extract did not affect the viability of eggs, although the values varied between of 51.7% the 80.6%. Larvae recently hatched from eggs were placed in glass tubes containing a tomato leaflet previously immersed for five seconds into the extract, at concentrations of 2000, 4000, 6000 and 8000 mg L-1 and conditioned on BOD at 27±1°C; 65±10% RH and 12 hours of light. By the fourth day after treatment the extract caused mortalities of 82, 68, 94.7 and 100%, respectively. By the sixth day, all concentrations caused 100% mortality of the larvae. The controls with water and methanol presented mortalities of 4 and 8%, respectively.