Potencial de Tagetes minuta (Asteraceae) para o manejo de Ascia monuste orseis (Lepidoptera: Pieridae) em cultivos orgânicos de brássicas no município de Pelotas, RS, Brasil

Abstract

Currently, the demand for healthy foods and for the ways of production that are less harmful to the environment and human has led some researchers study about sustainable production systems. In this context, the use of bioactive plants and techniques used by farmers are being used as alternatives for the insect management in production systems with ecological basis. Thus, the aim of this study was to evaluate the potential of Tagetes minuta (Asteraceae) in the management of Ascia monuste orseis (Lepidoptera: Pieridae) in kale (Brassica oleracea var. acephala DC). The study included laboratory bioassays and field experiments. In the laboratory, it has been evaluated: leaf consumption (with and without choice), insect biology (intake action and contact) and action on postures. In the bioassay of no-choice consumption, the treatments were made in leaf and flower extract using 10 and 30% (v/v) with and without adjuvant (flour 1% v/v) and essential oil of flower and leaf 0.25, 0.5 and 1% (v/v) for feeding caterpillars after three days they had hatched. In leaf consumption of freechoice, the treatments were the flower and leaf extract, 10 and 30% (v/v) and essential oil of flower and leaf 0.5 and 1% (v/v) applied to the food of caterpillars after six days they had hatched. Life biology by ingestion and contact with the flower and leaf extract treatments 10 and 30% (v/v) with and without adjuvant (flour 1% v/v) and essential oil of flower and leaf 0.25, 0.5 and 1% (v/ v) and ovicidal action of flower extracts 10 to 30% (v/v) with and without adjuvant (flour 1% v/v), and flower essential oil, 25, 0.5 and 1% (v/v) on eggs. All the bioassays were compared to the witnesses: water and neem oil 1% (v/v). In the field experiment, it has been applied weekly on kale, the aqueous extracts of flo wer and leaf T. minuta 30% (v/v) with adjuvant, compared to distilled water witness for the management of phytophagous insects. The resu lts of the bioassays in the laboratory have shown that the leaf consumption with and without choi ce, the flower extract 10% (v/v) reduced the leaf consumption. In insect biology, flower and leaf extracts were effective in the intake action, the same way th at extracts and essential oils of leaf were effective in the contact action. While the essential oil of flower and leaf 1% (v/v) and flower oil (0.5%, 1% vvv) were effective, respectively, in the reduction of mortality and hatching of caterpillars. In the field experiment the flower and leaf extracts 30% (v/v) using adjuvant reduced the population of phytophagous insects in kale. In short, the results show the potential of T. minuta for the management of A. monuste orseis by setting as a phytoprotection alternative that can be used in agro-ecological production of brassica.