Potencial bioinseticida de extratos de Cladonia substellata Vainio sobre pragas de feijão armazenado

Abstract

During storage, grains, seeds and byproducts are subject to attack by pests, which cause qualitative and quantitative losses as reduces the nutritional value of the product and business. To avoid losses chemicals are used, many of which are showing failures in control, which has led to its widespread use. In search of new alternatives, research is being conducted with the goal of developing natural products. Given the diversity of substances extracted from lichens and knowledge about their biological activity, in this work the insecticidal potential of extracts of the lichen Cladonia substellata on beetles Callosobruchus maculatus and Zabrotes subfasciatus to evaluate the toxicity (repellent effect) and bioactivity on mortality, oviposition and emergence of insects in stored beans. For this, we used the meeting and ethereal extracts of C. substellata, which were obtained by successive extractions of exhaustion of the stem liquênico. The extracts were tested separately at rates of 0,02, 0,006 and 0,002 mg / mL on beans Vigna sp, to C. maculatus, and at doses of 0,02 and 0,002 mg / ml on Phaseolus sp beans to Z. subfasciatus. Analysis of thin layer chromatography (TLC) confirmed the presence of usnic acid as major compound. The extracts and ethereal meeting of C. substellata showed repellent effect and caused mortality with increasing dosages utilized in both insects. These results indicate that extracts of C. substellata act on the immature stages of C. maculatus and Z. subfasciatus, usnic acid being present in these extracts probably responsible for the effect ovicidal / larvicidal observed. Further studies with extracts of the lichen C. substellata should be conducted with other concentrations, to evaluate the selectivity and possible effects on the viability and germination of bean seeds.