Insecticidal Activity of Essential Oils from eleven Eucalyptus spp and two hybrids: lethal and sublethal effects of their major components on Blattella germanica.

ALZOGARAY RA; LUCÍA A; ZERBA EN; MASUH HM

JOURNAL OF ECONOMIC ENTOMOLOGY

ENTOMOLOGICAL SOC AMER

Lugar: Lanham MD; Año: 2011 vol. 104 p. 595 - 606

0022-0493

The aim of the present study was to evaluate the fumigant activity of the essential oils from eleven species of the genus Eucalyptus and two of their hybrids on first instar nymphs of Blattella germanica L. The fumigant activity and repellence of the four major monoterpene components of these essential oils were also tested. Fumigant activity was evaluated by exposing nymphs to the vapors emitted by 50 µl of essential oil or monoterpene in a closed recipient. The lowest Knockdown Time 50% (KT50) values, expressed in minutes, were elicited by the essential oils of the E. grandis x E. tereticornis hybrid (57.9), E. sideroxylon (62.0), E. grandis x E. camaldulensis hybrid(63.8), E. viminalis (64.1), E. dunii (64.5), and E. grandis (68.7). The KT50 values for the remaining essential oils ranged between 74.5 (E. saligna) and 161.4 min (E. tereticornis). The essential oil from the hybrid E. grandis x E. tereticornis was 3.7 times less toxic than dichlorvos (positive control). The KT50 values of monoterpenes were 38.8 for alfa-pinene, 55.3 for 1,8-cineole, 175.6 for p-cymene, and 178.3 for gamma-terpinene. Alfa-pinene was 2.5 times less toxic than dichlorvos. There was a strong positive correlation between the fumigant activity of essential oils and their corresponding 1,8-cineole and alfa-pinene concentration. Repellency was quantified using a video tracking system. Two concentrations of monoterpenes were studied (7 and 70 µg/square cm). All compounds produced a light repellent effect but only when applied at 70 µg/square cm>. In all cases, the repellent effect was less than that produced by the broad-spectra insect repellent N,N-diethyl-3-methylbenzamide (DEET) (positive control).