Toxicidade do extrato de Derris Amazonica Killip a adultos de Cerotoma Arcuatus Olivier, 1791 (Coleoptera: Chrysomelidae)

Abstract

The abundance and recognized insecticidal activity of Derris amazonica in addition to the need of controlling Cerotoma arcuatus led to the present study, whose objective was to assess the toxicity of the extract of D. amazonica to adults of C. arcuatus. The concentration-response bioassays were carried out using three distends methodologies Ingestion of treated leaves, contact in treated surface (filter paper) and topical application. Mortality and leaf consumption results were subjected to regression analyses and probit analyses was used to estimate the median lethal values (i.e., LC50, LT50 and LD50). The extract of D. amazonica contains 3.7% of rotenone and was toxic to C. arcuatus when exposed to treated leaves (LC50 = 15.14 μl.ml-1), treated surface (LC50 = 0.45 μl.cm-2) or subjected to topical exposure (LD50 = 1.44 μl.g-1). Mortality levels higher than 80% and lower times were obtained with 5% (v.v-1) of the extract. Leaf consumption by C. arcuatus in the leaf-ingestion bioassay was smaller than in the topical bioassay. In both cases though higher extract concentration led to lower leaf consumption with phagoinhibition taking place at concentrations as low as leaf 1% (v.v-1). The extract of D. amazonica was toxic to C. arcuatus and inhibit its feeding with higher efficiency with ingestion of treated leaves.