Essential Oils As Alternative Antifungal Agents For The Citrus Industry In South Africa -A Review

Abstract

The South African citrus industry has been contributing greatly to the economy’s Gross Domestic Product (GDP) for a very long time. Citrus plantations in the country have been growing since the 1600s and the industry has grown enormously over the years. The industry provides 125 000 employees annually and the numbers are expected to increase. Furthermore, most of the citrus fruits produced are exported to foreign countries such as the United States of America (USA) and European Union countries (EU) as it provides great income return. However, the recent widespread problems of the Citrus black spot (CBS) have resulted in serious concern. CBS is caused by the fungus Phyllosticta citricarpa which affects almost all commercial citrus species. These losses not only affect profit margins and initial input costs but also lower retailer and consumer confidence in the marketplace. Symptoms and yield losses caused by CBS infection are usually minimized by the application of synthetic fungicides during the fruit susceptibility period. Synthetic fungicides are the primary means of controlling fungal pathogens. However, fungal pathogens have shown a concerning trend against these fungicides. Additionally, they are known to remain on the plant or within its tissues following treatment resulting in potentially toxic and carcinogenic effects on humans. To reduce the use of synthetic fungicides in the food chain, alternative methods to synthetic fungicides are needed. Hence, natural plant products such as essential oils and hydrosol are gaining attention from researchers globally due to their antimicrobial, biodegradable, eco-friendly, economical and safe properties.