Study and evaluation of the toxicity of essential oils from brazilian peppertree (Schinus terebinthifolius Raddi) and bushy matgrass (Lippia alba [Mill.] N.E.Br ex Britton & P. Wilson): an organic approach for seed protection against bean weevil (Callosobruchus maculatus Fabricius, 1775)
botanical pesticide, stored seed pest, cowpea.
The continuous use of synthetic pesticides has raised concerns about their residual effects on both the environment and human health, as well as an increase in agricultural pests resistance. Alternative methods are studied as a way of mitigating these consequences, and among them is the use of essential oils as a manner of controlling pests. This work aimed to assess the fumigation effects of 12 essential oils of different chemical compositions from genotypes of two plant species: Lippia alba (UFRRJ-ECB-021/022-QT: citral/limonene, UFRRJ-ECB-037/029/016-QT: citral, UFRRJ-ECB-003/008-QT: carvone/limonene e UFRRJ-ECB-028-QT: linalool) e Schinus terebinthifolius (UFRRJ-ARO-011-QT: α-pinene, UFRRJ-ARO-050-QT: sabinene, UFRRJ-ARO-079-QT: α-phellandrene/α-pinene, UFRRJ-ARO-025-QT: β-pinene/α-pinene, UFRRJ-ARO-032-QT: δ-carene/α-pinene, UFRRJ-ARO-094-QT: limonene, UFRRJ-ARO-078-QT: α-phellandrene/sabinene e UFRRJ-ARO-022-QT: mircene) against the cowpea weevil, Callosobruchus maculatus. Concentrations in the range between 0.10 mg/mL of air and 1.00 mg/mL of air were used to evaluate aspects from insect reproductive cycle, such as: mortality, egg laying, emergence of new adults and emergence rate. Furthermore, larval hatching and bean grain mass preservation were assessed in assays with the oils of the S. terebinthifolius genotypes: UFRRJ-ARO-032-QT: δ-careno/α-pineno e UFRRJ-ARO-094-QT: limoneno and with all L. alba oils. The results indicated reproductive cycle inhibition occurs in all oils tested, with the UFRRJ-ECB-028-QT:linalool oil having the lowest LD50 (0.1017 mg/mL of air). L. alba oils achieved better control of C. maculatus reproduction and improved seed protection.