Phythopthora palmivora fungal pathogen is the cause of cocoa's current slump of production in Indonesia. This has prompted the Government of Indonesia to initiate a rehabilitation by replanting 450 000 ha to boost national cocoa [Theobroma cacao] bean production to 1 million tons in 2013. Since 2006, the Province of West Sumatra has selected to support the program in the western part of Indonesia. As the result, the development of cocoa planting area in West Sumatra increase significantly less in a decade, from 25 000 ha in 2005 to 137 355 ha in 2013. However, its productivity constrained due to pests and diseases, mainly black pod disease caused by Phytophthora palmivora. Therefore, the average of cocoa yield in this province only 300-700kg / ha while its genetic potential is up to 2000 kg / ha. The purpose of this research was to study in vitro the fungicide effect of formulated essential oils of Ellettariopsis slahmong and Cinnamomum burmanii against P. palmivora. The method used was completely randomized design [CRD] in factorial. The first factor was the type of essential oil formulas: Cinnamomum burmanii litterfall leaf essential oil, wild Zingiberaceae Ellettariopsis slahmong essential oil, and a mixture of them both. The second factor was the level of concentration of essential oils starting from 250 ppm, 500 ppm, 750 ppm and 1000 ppm per 100 mL of potato dextrose agar [PDA] media and control. Observation parameters were the diameter of colonies, colony growth velocity, biomass of colony and resistance test. The best result was the mixture treatment of essential oils of wild Zingiberaceae Ellettariopsis slahmong and Cinnamomum burmanii litterfall leaf by using concentration of 1000 ppm. The treatment successfully inhibited P. palmivora colony growth, miselium and hyfa. This result strongly indicated that the combination of these essential oils can be developed as a bio fungicide.
