[Egg distribution of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and the parasitism by Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)]

Lethal and sublethal effects of essential oils fromPiper capitarianumYunck andPiper krukoffiiYunck onPlutella xylostellaL

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.

Bioactivity of aqueous extract of Jacaranda spp. (Bignoniaceae) on Plutella xylostella L. 1758 (Lepidoptera: Plutellidae)

Abstract The high consumption rate of vegetables stimulates the cultivation and increases the demand regarding the adequacy of the production processes. The attack of the pest Plutella xylostella causes high losses by reducing product quality, typifying a phytosanitary problem. This study aimed to verify the bioactivity of aqueous extracts of leaves of Jacaranda decurrens and Jacaranda mimosifolia at concentrations of 5, 10, and 15% on the insect. The choice test was carried out at the laboratory to determine the food effect of plant extracts and evaluate changes in the life cycle of insects exposed to active compounds through the analysis of biological parameters. Plant extracts of J. decurrens and J. mimosifolia presented with phagodeterrent classification in the choice experiments. The three J. decurrens extract concentrations promoted a prolongation of larval and pupal duration, while the duration of individuals treated with J. mimosifolia at 10% was significantly reduced. Occurred reduction in larval survival of individuals treated with aqueous extracts of J. decurrens and J. mimosifolia. Eggs from treatments with aqueous extract of J. decurrens and J. mimosifolia had reduced survival. Pupal survival of individuals treated with extract at 15% showed a significant reduction compared to the treatments at 5% and 10%. Pupae from the treatment with aqueous extract of Jacaranda mimosifolia showed a reduction in biomass in the treatment at 15% differing from the control e 5%. Thus, the aqueous extracts of the species J. decurrens and J. mimosifolia show insecticidal potential in the tests performed on P. xylostella.