EFFICACY OF LEMON GRASS OIL ON THE MANAGEMENT OF ROOT ROT OF OKRA [FUSARIUM SOLANI (MART.) SACC]

Abstract

Background: Okra (Abelmoschus esculentus L.) is an important vegetable crop cultivated in tropical and subtropical regions. Its production is threatened by root rot caused by Fusarium solani, leading to severe yield losses. Conventional management relies on synthetic fungicides, which are effective but associated with adverse effects on human health, soil microbiota, and environmental safety. Botanical alternatives such as lemongrass oil, containing bioactive antifungal compounds, have emerged as safer, eco-friendly strategies for sustainable crop protection.

Objective: This study aimed to determine the incidence of okra root rot in District Charsadda and to evaluate the antifungal efficacy of lemongrass oil against F. solani under both in vitro and in vivo conditions.

Methods: A field survey was conducted across fifteen okra-growing localities in Charsadda during April–May 2021 at the seedling stage. Seedling mortality percentage was calculated from five representative fields at each site. Infected seedlings were collected, and F. solani was isolated and confirmed morphologically. In vitro bioassays employed lemongrass oil at concentrations of 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% using the food poisoning technique, with Mancozeb as a positive control. In vivo experiments were performed in a screen house, where okra seeds were sown in sterilized soil and artificially inoculated with F. solani. Treatments were arranged in a Completely Randomized Design (CRD) with five replications, and data were statistically analyzed using ANOVA and LSD tests.

Results: Root rot prevalence in Charsadda ranged from 9.00% in Rahim Abad to 20.14% in Bad Shah Kali, with a mean mortality of 13.27%. In vitro, lemongrass oil at 3% reduced colony diameter by 76.10%, biomass by 76.60%, and spore concentration by 97.29% compared to control. In vivo, seedling mortality decreased to 16.00% and germination increased to 84.00% at 3% concentration, while untreated controls showed 84.00% mortality and 16.00% germination. Lower concentrations (0.5% and 1%) were less effective.

Conclusion: Lemongrass oil significantly suppressed F. solani and improved seed germination in both laboratory and screen house conditions. At 3% concentration, it proved highly effective, supporting its potential as a sustainable botanical alternative to chemical fungicides for okra root rot management.