The controlled crossing on Eucalyptus species as a potential technique to improve the pediculicidal activity of essential oils

LUCIA A & TOLOZA AC, MASUH H, GONZALEZ-AUDINO P, ZERBA E AND PICOLLO MI

Buenos Aires

Congreso; 3er Internacional congress on phthiraptera,; 2006

Previous reports have shown the permethrin resistance problems concerning human louse control from Buenos Aires, Argentina. One alternative to synthetic pyrethroids is the use of essential oils due to their low mammalian toxicity. A previous study have shown the effective fumigant activity of the essential oils of Eucalyptus species and their main components such as 1.8 cineole and α-pinene. The purpose of the present work was to study the fumigant activity of five Eucalyptus essential oils-E. grandis, E. camaldulensis, E. tereticornis and their hybrids E. grandis x E. camaldulensis and E. grandis x E. tereticornis- against permethrin-resistant head lice from Buenos Aires. Essential oils were obtained by hydrodistillation of vegetal material collected in an experimental plot of our laboratory. Head lice were collected from heads of infested children 5-12 yr old, using an antilouse comb. Fumigant activity was evaluated in an enclosed chamber. The number of knockdown head lice was recorded every 5 min for 1h, and then a Probit analysis was made to determine the knockdown time 50% (KT50) of the tested essential oils. There was a significant difference of vapor effect among the hybrids and their parents. Both hybrids were more effective than its parents. E. grandis x E. camaldulensis and E. grandis x E. tereticornis showed KT50 values of 12.99 and 13.63 min, respectively;  while E. grandis, E. camaldulensis and  E. tereticornis showed values of  KT50 of 25.57, 35.14 and 31.31min, respectively. It is interesting to note that the GC-MS analysis showed cuali-cuantitative differences in the essential oil composition of the hybrids, in comparison with their parents. Additionally, yields obtained from hybrids individuals were almost two times greater than those obtained from their parents. Our results suggest the potential use of the controlled crossings technique to obtain increased yield and higher effective essential oils against head lice.