OIDA International Journal of Sustainable Development
Open-access peer-reviewed journal
https://doi.org/10.64211/oidaijsd190811
In Vivo Antifungal Control of Citrus Black Spot (CBS) Using Thyme Oil as an Alternative to Synthetic Fungicides
Bheki Thapelo Magunga
Department of Environmental Health, Faculty of Health Science, University of Johannesburg, South Africa.
Corresponding author: bhekim@uj. ac.za
Volume 19, Issue 08, Pg. 167-174, 2026.
Abstract: The spread of Citrus black spot (CBS) is a major concern in citrus industry as it threatens fruit marketability and citrus tree health. Additionally, there are public concerns about the safety and side effects of synthetic fungicides used to control CBS. Synthetic fungicides are reported to be carcinogenic to humans and toxic to the environment. microorganisms often develop resistance to synthetic fungicides. This has prompted research into the identification of new ways with broad activity in treatment of microbial disease in plants such as the use of essential oils (EOs). Previous study by Magunga (2023) has proven the effectiveness thyme oil in vitro in the treatment of CBS using the agar diffusion bioassay, minimum inhibitory concentration (MIC) and scanning electron microscopy (SEM), furthermore the study indicated that the life cycle of CBS revolves around the citrus leaves and the fruits, however no study has been done in vivo to treat CBS using Thyme oil. The study current study aimed to investigate the use of thyme oil in vivo as an alternative antifungal treatment for CBS on lemon leaves and fruits. Thyme oil effectiveness together with that of its hydrosol, was tested in vivo on healthy lemon leaves and fruits infected with Phyllosticta citricarpa (CBS causative agent) as these are parts of the life cycle of the CBS infection. The results showed that Thyme oil demonstrated the highest severity of reduction because it almost completely inhibited fungal growth on the leaf and on the fruits surface. This indicates that Thyme oil can be used as potential alternative antifungal agents against CBS.
Keywords: Citrus Black Spot; Phyllosticta citricarpa; Thyme oil; essential oils; Hydrosol
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