Toxicidade, deterrência e repelência de extratos aquosos de Cabralea canjerana ssp. polytricha (a. juss.) penn. (Meliaceae) sobre o curuquerê-da-couve ascia monuste orseis (godart) (Lepidoptera: pieridae) Translated title: Toxicity, deterrence and repellence of aqueous extracts of Cabralea canjerana ssp. polytricha (Meliaceae) on ascia monuste orseis (Lepidoptera), the cabbage caterpillar

Abstract

Este trabalho avaliou, em laboratório, a toxicidade, a repelência e a deterrência de extratos aquosos de sementes, de folhas e de frutos de Cabralea canjerana ssp. polytricha (Meliaceae) sobre o curuquerê-da-couve Ascia monuste orseis (Lepidoptera). Extratos aquosos a 3, 5 e 10% foram obtidos por infusão do material biológico seco triturado em água destilada e filtrado após 24 h. Dentro de 48 h após o preparo, folhas de couve foram mergulhadas nos extratos ou em água destilada e utilizadas para avaliar o efeito dos extratos na percentagem de sobrevivência e no tempo de vida das larvas. A repelência e a deterrência dos extratos foram avaliadas em testes com e sem chance de escolha de folhas tratadas ou não, avaliando-se, comparativamente, a área consumida e o número de larvas por porção foliar. Houve 100% de mortalidade das larvas nos tratamentos, em contraste com a sobrevivência de 87% delas no controle. Larvas alimentadas com folhas tratadas sobreviveram significativamente menos que larvas do controle. Ao contrário de extratos de folhas e frutos, extratos de sementes apresentaram efeito repelente, mas não intenso o suficiente para evitar o consumo foliar. Houve redução no consumo foliar pelas larvas submetidas ao extrato a 10% nos experimentos com chance de escolha. Quando larvas não tiveram opção de consumir folhas sem extratos, alimentavam-se de folhas tratadas, porém com menor consumo, principalmente nas concentrações de 10 e 5%.

Translated abstract

The toxicity, deterrence and repellence of aqueous extracts of seeds, leaves and fruits of Cabralea canjerana ssp. polytricha (Meliaceae) on the cabbage caterpillar, Ascia monuste orseis (Lepidoptera), were evaluated in laboratory. Aqueous extract of 3, 5 and 10% were obtained by infusion of dried and pulverized biological material in distilled water, filtered after 24h. Within 48h after preparation, cabbage leaves were immersed in the extracts or in distilled water and used in tests to verify differences on larval survival and on larval life-time between control and treatments. Extract repellency and deterrence were evaluated in free and non-free-choice tests for treated and non-treated cabbage leaves, by comparisons among the consumed area and the number of larvae per leaf portion. It was observed 100% larval mortality in the treatments in contrast to the 87% survival rate in the control. Larvae fed on treated cabbage leaves did not live as much as the control ones. Seed extracts, contrary to leaf and fruit extracts, had a repellent effect but it was not sufficiently intense to avoid leaf consumption. It was observed a reduction on larval leaf consumption in all free-choice treatments using 10% extracts. When the larvae did not have the option to consume non-treated leaves, they fed on treated leaves, but consuming smaller portions, especially when 10 and 5% extracts were used.