The Preventive and Curative Potential of Morinda citrifolia Essential Oil for Controlling Anthracnose in Cassava Plants: Fungitoxicity, Phytotoxicity and Target Site

Controlling anthracnose in crops usually depends on synthetic chemicals, but essential oils offer a promising alternative with a potentially lower risk to human health and the environment. This study examines the use of noni (Morinda citrifolia L.) essential oil for preventive and curative control of anthracnose in cassava plants. Extracted from ripe noni fruit, the oil was tested at concentrations of 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, and 5.0 µL/mL for its antifungal properties against Colletotrichum species isolated from cassava. We applied the oil both preventively and curatively, monitoring for phytotoxic effects. Phytochemical analysis revealed that the main compounds were octanoic acid (64.03%), hexanoic acid (10.16%), and butanoic acid (8.64%). The oil effectively inhibited C. chrysophillum and C. musicola at 2.0 µL/mL, while C. truncatum required 5.0 µL/mL for significant inhibition. Higher concentrations reduced disease progression but showed phytotoxicity at only 5 µL/mL. Molecular docking suggested that octanoic acid interacts with the fungi’s tyrosine-tRNA ligase enzyme, hinting at its mechanism of action. Collectively, our findings reinforce the potential of noni essential oil as an alternative agent against Colletotrichum spp. in cassava crops.