Abstract Plutella xylostella (L.) is responsible for considerable vegetable crop losses in the metropolitan region of Manaus, Brazil. In recent decades, essential oils have been investigated as an alternative to synthetic insecticides. The genusPiperis widely distributed in Amazonia and essential oils from these plants have insecticidal properties. This study describes the chemical composition of the essential oils fromPiper capiterianumandPiper krukoffiias well as the lethal and sublethal effects onP. xylostella. The phytotoxicity of the oils on the host plant was also evaluated. Globulol was the major constituent of theP. krukoffiioil ando-cymene was the major constituent of theP. capitarianumoil. The oil fromP. capiterianumexhibited greater toxicity to larvae and eggs. This oil also presented greater repellant action, feeding deterrence and mild phytotoxicity to the host plant (Brassicae oleraceae). The findings suggest that this oil can be used in the preparation of a formulated insecticide for the management ofP. xylostellain different development phases. However, further studies are needed to evaluate the effect of this oil on crops under field conditions as well as non-target organisms and determine the cost-benefit ratio of a product formulated withP. capitarianumoil.

O objetivo deste trabalho foi verificar os efeitos dos óleos de pinhão-manso e neem na eclosão de lagartas de Diatraea saccharalis (Fabr., 1794). Os testes foram conduzidos em câmaras climatizadas a 25 ± 2° C, UR de 70 ± 10% e fotofase de 12 horas. Os tratamentos foram compostos por: água destilada (testemunha); solução aquosa de óleo de pinhão-manso a 3%; solução aquosa de óleo de neem a 3% e solução aquosa de óleo de pinhão-manso + óleo de neem a 3%. Foram utilizados 250 ovos de D. saccharalis com até 24 horas de idade, por tratamento. Cada massa de ovos contendo 50 ovos, constituindo uma repetição, foi imersa três vezes, durante um segundo, nos respectivos tratamentos. Em seguida, os ovos foram distribuídos em placas de Petri (5 cm de diâmetro) contendo no fundo papel filtro umedecido com água destilada, para evitar o ressecamento das massas de ovos. Foram avaliados o período embrionário e a porcentagem de lagartas eclodidas de D. saccharalis. Verificou-se efeito tóxico dos óleos vegetais sobre a eclosão das lagartas da broca-da-cana, constatando-se diferenças. Observou-se que, no tratamento com neem, apenas 42,4% das lagartas eclodiram. Para o tratamento de pinhão-manso + neem ocorreu 70% da eclosão das lagartas e com o óleo de pinhão-manso, 60% de lagartas eclodidas. Foi verificado também um alongamento do período embrionário, principalmente do tratamento com óleo de pinhão-manso (7,09 dias). Podendo-se inferir que os óleos de pinhão manso e neem afetaram a eclosão das lagartas de D. saccharalis, apresentando efeito inseticida.

The aim of this study was to evaluate the effects of physic nut and neem oil on the hatching of caterpillars of Diatraea saccharalis (Fabr., 1794). Tests were conducted in acclimatized chambers at 25 ± 2° C, RH 70 ± 10% and photophase of 12h. The treatments were: distilled water (control), aqueous solution of physic nut oil at 3%; aqueous solution of neem oil at 3%, and aqueous solution of physic nut and neem oil, both at 3%. A total of 250 eggs from D. saccharalis up to 24 hours of age were used for each treatment. Each egg mass containing 50 eggs, constituting one repetition, was immersed three times, for one second, in the respective treatments. Then the eggs were distributed in Petri dishes (5 cm diameter) containing filter paper moistened with distilled water at the bottom to prevent drying of the egg mass. Evaluations were made of the embryonic period and the percentage of hatched larvae of D. saccharalis. Differences were found that indicate that the vegetable oils had a toxic effect on the hatching of sugarcane borer larvae. In the treatment with neem oil only 42.4% of the eggs hatched. In the treatment with physic nut + neem oil 70% of the eggs hatched, and in the treatment with physic nut oil 60% of the eggs hatched. An increase in the embryonic period was also observed, particularly in the treatment with physic nut oil (7.09 days). It can be inferred that the oils of neem and physic nut affected the hatching of D. saccharalis eggs, with an insecticide effect.