Chemical Fungicides and Antagonists as Potential Treatments for Ganoderma lucidum-Associated Basal Stem Rot in Mandarin Trees

Ganoderma lucidum causes basal stem rot disease in mandarin trees, resulting in a variety of symptoms including dieback, foliage discoloration, an unhealthy appearance and eventual tree declines or death. Prior to field application, it is imperative to assess the efficacy of newer molecules and possible potential antagonists through In vitro testing. In this study, ten chemical fungicides and four antagonists were evaluated for their effectiveness against G. lucidum using the poison food method and dual culture technique, respectively. Among the chemical fungicides tested, Copper oxychloride 50% WP (@3g/l), Fluxapyroxad 167 G/L + Pyraclostrobin 333 G/L SC (@0.6 g/l), and Metiram 55% + Pyroclostribin 5% WG (@1g/l) demonstrated the highest effectiveness, entirely suppressing (100%) pathogen growth. In the dual culture technique, the fungal antagonists Trichoderma harzianum (79.63%) and Trichoderma asperellum (77.57%) exhibited superior effectiveness compared to Pseudomonas fluorescence and Bacillus subtilis against G. lucidum. These findings highlight the efficacy of chemical fungicides and antagonists in treating G. lucidum-induced basal stem rot in mandarin trees.