Electrophysiological responses of eucalyptus brown looper Thyrinteina arnobia to essential oils of seven Eucalyptus species

Eucalyptus is frequently attacked by the Brazilian eucalyptus brown looper, Thyrinteina arnobia. This caterpillar is regarded as the main lepidopterous pest of Eucalyptus and yet no practical and environmentally acceptable method of control currently exists. Electroantennographic techniques (EAG) have never before been used to detect semiochemicals that affect the behavior of T. arnobia. Thus, in this work, the ability of T. arnobia males and females to detect volatile essential oils of seven Eucalyptus species was investigated by EAG. We demonstrated that T. arnobia antennal olfactory system clearly showed differential sensitivity to several compounds, by coupled gas chromatography-electroantennographic detection (GC-EAD). Twenty-eight compounds were identified that elicited responses in T. arnobia, indicating that GC-EAD analysis may well be a useful means of screening active plant extracts for compounds that contribute to the observed behavior of this defoliator. The results also suggest that this species uses several volatile cues to find its host.