Antifungal activity of essential oils over cocoa witches’ broom

Abstract

The cocoa (Theobroma cacao) witches’ broom, caused by Moniliophthora perniciosa (= Crinipellis perniciosa), is the one of the worst diseases of cocoa plantations worldwide. The aim of this work is to contribute with an alternative to control this disease, therefore it was studied the effect of different concentrations of essential oils from the aromatic species Ocimum selloi, Mentha arvensis and Syzygium aromaticum on the mycelial growth and germination of basidiospores of M. perniciosa. Essential oils were extracted by hydro distillation in a Clevenger apparatus. Essential oils were added in melted culture medium BDA (potato dextrose agar) and poured into Petri plates for evaluation of mycelial growth. The treatments consisted of seven concentrations of each oil: 0, 0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 µL.mL-1 with six replicates each in a randomized design. The same amounts of essential oils dissolved in distilled water were used to test the basidiospores germination of the fungus. There was a gradual reduction in the rate of mycelial growth of M. perniciosa with increasing doses of essential oils, achieving 100% inhibition of mycelial growth when used at a concentration of 0.75 µL.mL-1  for all the essential oils tested. There was total inhibition of germination of M. perniciosa at concentrations of 1.00 µL.mL-1 for oil of M. arvensis, and 0.75 µL.mL-1  for oil of O. selloi e S. aromaticum.