Host Range and Chemical Control of Cercospora citrullina, the Causal Agent of Watermelon Spot Disease.

Abstract

This study systematically evaluated cultivation requirements, host range, and chemical control options for Cercospora citrullina causing watermelon spot disease. Among 11 chemically defined media tested, corn meal agar medium supported optimal mycelial growth of C. citrullina, with an average radial growth rate of 56.72 ± 1.45 mm under controlled conditions (25°C, darkness). Host range determination via artificial inoculation of 19 plant species confirmed that the host range of the strain UNL090101 is limited to the Cucurbitaceae species tested, with watermelon (Citrullus lanatus) exhibiting the highest susceptibility, followed by melon (Cucumis melo) and cucumber (Cucumis sativus). Fungicide screening of 17 commercial formulations identified 40% iminoctadine tris (albesilate) WP (EC50 = 2.82 μg·liter-1) and 64% mancozeb + 8% cymoxanil (WS) (EC50 = 48.75 μg·liter-1) as the most effective treatments, achieving control efficacies of 74.47 and 58.62%, respectively. These findings provide actionable guidelines for optimizing crop rotation, intercropping strategies, and fungicide selection in watermelon production systems.