Corymbia spp. and Eucalyptus spp. essential oils have insecticidal activity against Plutella xylostella

• Published in: Industrial crops and products Vol. 109; pp. 374 - 383
• Main Authors: Filomeno, Claudinei Andrade, Barbosa, Luiz Claudio Almeida, Teixeira, Robson Ricardo, Pinheiro, Antônio Lelis, de Sá Farias, Elizeu, de Paula Silva, Eliete Meire, Picanço, Marcelo Coutinho
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-12-2017
• Subjects: (-)-Isopulegol; Citronellal; Corymbia; Essential oils; Eucalyptus; Insecticidal activity; Citronellal; (-)-Isopulegol; Eucalyptus; Insecticidal activity; Essential oils; Corymbia
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2017.08.033

•The composition of essential oils from E. andrewsii, E. pyrocarpa and C. ptychocarpa is reported for the first time.•Essential oils from C. citriodora are highly toxic towards P. xylostella.•A mixture of citronellal and (-)-isopulegol exhibited outstanding contact toxicity towards P. xylostella larvae.•The essential oils from C. citriodora are more toxic to P. xylostella than commercial neem oil.•Insecticidal activity of citronellal against P. xylostella is enhanced by (-)-isopulegol.
Plutella xylostella (L.) is the main brassica pest worldwide and is difficult to control even with commercial insecticides. In this study, assessments were made of the contact toxicity of essential oils (EOs) from ten Myrtaceae species. For this, the leaves of four Corymbia species (C. citriodora, C. intermedia, C. maculata, and C. ptychocarpa) and six Eucalyptus species (E. andrewsii, E. crebra, E. punctata, E. pyrocarpa, E. siderophloia, and E. sphaerocarpa) were collected during the Brazilian dry season and subjected to hydrodistillation for extraction of EOs. For C. citriodora, another sample was also collected during the rainy season. The essential oil (EO) content of all samples ranged from 0.07% w/w to 3.3% w/w and GC–MS analyses allowed the identification of 52 compounds. For E. andrewsii, E. pyrocarpa, and C. ptychocarpa there was no previous report on EO chemical composition. For C. citriodora, a higher EO content for the samples collected during the dry season was found (2.72% versus 1.53% for the rainy season). The insecticidal activity of all eleven EOs was evaluated via topical application on the second-instar larvae of P. xylostella. The most active EOs were produced by C. citriodora collected during the dry season, with citronellal (86.8%) and isopulegol (4.7%) being the main constituents. At 30μg/mg of insect, these EOs caused 80% P. xylostella mortality, being more active than neem oil used as positive control. These EOs presented low toxicity for Solenopsis saevissima, a natural predator of P. xylostella. Bioassays also demonstrated a synergistic effect between citronellal and (-)-isopulegol at all tested proportions. The results described here suggest that C. citriodora EOs can be an environmentally friendly alternative method to control P. xylostella.