Bioatividade de extratos aquosos de espécies de rubiaceae juss. sobre Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) e determinação dos compostos fenólicos

Abstract

The diamondback moth (Plutella xylostella) (Linnaeus, 1758) (Lepidoptera: Plutellidae) is a major factor limiting the development of brassicas in the world, due to the serious damages that cause in production. Chemical control is still the most used in the control of DBM because of its convenience, speed and efficiency in population control, but unsuitable applications come selecting populations resistant to marketed products, as well as causing contamination and soil infertility, beings of intoxication living and dwindling natural enemies. Thus, an alternative that does not cause so much damage to the environment is the use of plant extracts, as a selective technique, its low toxicity and effectiveness against various agricultural pests. In this context, the aim of this study was to evaluate the effects of aqueous extracts of Alibertia edulis, Amaioua intermedia and Alibertia sessilis Rubiaceae Juss. in the biological cycle of diamondback moth. For this, cabbage leaf disks, 8 cm in diameter were immersed in aqueous extract (10 g/ml) for 30 seconds. The witness disks was immersed in distilled water. After this period, the discs were placed on filter paper at room temperature to remove excess moisture, and were subsequently transferred to Petri plates. In each Petri dish were inserted into a larvae of Plutella xylostella newly hatched (0-24 hr). The tests were conducted at a temperature of 25 ± 2°C, 55 ± 5% RH and a photoperiod of 12 h. The biological parameters were evaluated: duration and viability of larval and pupal stages, pupal weight, female longevity and males in days, sex ratio, number of eggs, incubation period and egg viability. The extracts from the leaves of A. intermedia and A. sessilis negatively affected the development of DBM in all stages of development (larvae, pupae and reproductive), extending the duration of the larval stage, which resulted in no weight gain, these extracts caused major mortalities in both larval as pupal stage. Regarding the quantity and viability of eggs, A. intermedia had the lowest number of eggs and hatched larvae. The species A. edulis had the highest flavonoid content and A. intermedia had the highest total phenol content, but A. sessilis was the only one that obtained the presence of the five phenolic patterns tested.