The objective of this study was conducted to select of an essential oil from some medicinal plant for
inhibiting Didymella bryoniae, causal agent of Gummy Stem Blight of watermelon. The essential oils from 9 species
of tested plants were extracted by using water distillation method. The essential oils from tested plants were mixed
to PDA medium at 0.6% final concentration for fungal inhibition test. The results showed that the essential oils from
7 species consists of, wild ginger: Boesenbergia pandurata Holtr., ginger: Zingiber officinale Roscoe, Siamese
ginger: Alpinia galanga (L.) Willd., lemon grass: Cymbopogon citratus Stapf., leech lime: Citrus hystrix DC., hairy
basil: Ocimum americanum L. and sweet basil: O. basilicum Linn. could inhibit the mycelial growth of D. bryoniae
up to 100% on PDA medium. In addition, there was no significantly different when compared with using benomyl
fungicidal. Whereas an essential oil from curcuma: Curcuma longa Linn. showed partial inhibition to the mycelial
growth of D. bryoniae on PDA, and tangerine: C. reticulata Blanco. did not inhibit this fungal.