Atividade inseticida de óleos essenciais sobre Sitophilus zeamais Mots. (Coleoptera : Curculionidae)

Abstract

The essential oils are promising alternative for the management of Sitophilus zeamais in stored maize. In this investigation, toxicity, repellency and persistence of essential oils in stored maize were evaluated using S. zeamais. The oil’s LC50s from leaves of Piper hispidinervum, Eugenia uniflora, Cinnamomum zeylanicum, eugenol compound, Piper marginatum, Schinus terebinthifolius and Melaleuca leucadendron and green fruits of S terebinthifolius, in the tests of contact and ingestion were estimated at 1.0; 11.6; 14.2; 14.8; 21.1; 57.7, 75.8 and 98.8 μL/40g maize, respectively. In fumigation tests for adults, the LC50s ranged from 94.7 to 0.53 μL/L of air and the toxicity ratios ranged from 178.7 to 2.0. In the fumigation for larvae with 7 to 14 days of age, only eugenol did not differ from control concerning number of adults emerged. In larvae with 7 to 21 days, the oils of green fruits from S. terebinthifolius and P. hispidinervum showed the best performance in relation to the control. Percentages of repellency varied between 97.4 (P. marginatum and C. zeylanicum) to 81% (P. hispidinervum). In the initial storage period (after impregnation), mortality of S. zeamais ranged between 93.8 (P. hispidinervum, Melaleucaleucadendron and eugenol) to 100% (E. uniflora, green fruits of S. terebinthifolius and P. marginatum). From 30 days, mortality generally decreased, except for P. marginatum (92.2%). According to the regression equations adjusted for the number of S. zeamais emerged throughoutthe storage period, there was no statistical significance for the oils of S. terebinthifolius and P. marginatum and control. For the average, the oil from P. marginatum was the most persistent, providing emergency of only 0.30 insects differing from the other oils and the control.