Commercial plant essential oils obtained from 11 Myrtaceae plant species were tested for their antifungal activity against Phytophthora cactorum, Cryponectria parasitica and Fusarium circinatum. Good antifungal activity against Phytophthora cactorum was achieved with the essential oil derived from Leptospermum petersonii at 28 × 10⁻³ mg/ml air concentration. Inhibition rates of Eucalyptus citriodora and Melaleuca quinquenervia were 35.4% and 33.6% at 28 × 10⁻³ mg/ml air concentration, respectively. In a test with C. parasitica, inhibition rates of E. citriodora and L. petersonii were 29.4% and 38.5%, respectively. Only L. petersonii essential oil showed antifungal activity against F. circinatum. Analysis by gas chromatography–mass spectrometry led to identification of 16, 15 and 12 compounds, respectively, in the oils of L. petersonii, M. quinquenervia and E. citriodora. The antifungal activity of the identified compounds was tested individually using standard or synthesized compounds. The inhibition rates of citronellol, neral, geraniol and geranial were 100% against P. cactorum at 28 × 10⁻³ mg/ml air concentration. In a test with C. parasitica, the inhibition rates of neral and geranial were 61.7% and 68.9% at 28 × 10⁻³ mg/ml air concentration. Copyright © 2008 John Wiley & Sons, Ltd.