EFFECT OF THE BAMBOO PYROLIGNEOUS EXTRACT ON Plutella xylostella L. (LEPIDOPTERA: PLUTELLIDAE)

Abstract

The search for alternative methods for vegetable pest control has increased in the last years. The pyroligneous extract (PE), obtained from smoke condensation during wood charring, is a promising alternative for the ecological management of pest insects. The brassicas have their production affected by different pests, such as Plutella xylostella. The objective of this work was to evaluate the effect of pyroligneous bamboo extract (Bambusa vulgaris) on P. xylostella. The bamboo culms were collected from mature clumps at the germplasm bank of the Center for Agricultural Sciences - AL and pyrolised in a Jung model LT6 2010 tubular oven to obtain the bio oil. As PE is not completely soluble, an emulsion was prepared according to Senhorini's (2010) methodology, by testing different concentrations of Tween and Span. The PE was subjected to separation through funnel filtration to remove tar. Toxicity tests were performed to find the upper and lower mortality limits for both emulsion and filtered extract to estimate lethal concentrations. The repellence index and ovicidal effect of the emulsions were also determined. Of the five emulsions tested only the emulsion with 5 g of Tween, 10 g of extract and 85 g of water was stable, but without uniform toxic activity for caterpillar control, not fitting the Probit estimate; in the same way for the filtered extract. For repellence, only the 20% filtered extract after 30, 60, 120 minutes and 24 hours of the larvae inoculation was repellent and the other concentrations were neutral. For the ovicidal effect, only the concentration of 20% presented the highest average of unviable eggs (50.85%), contrasting with 2.8% of the control. It is concluded that the pyroligneous extract emulsion and the filtered extract do not have uniform toxic activity for P. xylostella larvae control, but the filtered extract has repellent effect and ovicidal action.