Efficacy of new fungicide molecules against Colletotrichum siamense causing arecanut leaf spot

Abstract

Leaf spot disease is a major constraint to arecanut (Areca catechu L.) production in different growing regions of the country, resulting in considerable yield losses. Although the disease can be managed through cultural practices, chemical control remains an essential component as cultural methods alone are often inadequate. In this study, the fungitoxic effect of different fungicides against the leaf spot pathogen was evaluated under in vitro conditions. A total of 20 fungicides, comprising eight systemic, six contact, and six combi formulations, were assessed against Colletotrichum siamense using the poisoned food technique. All the fungicides tested significantly inhibited the radial mycelial growth of the pathogen compared to the untreated control. Among them, Captan 50% WP and Chlorothalonil 75% WP recorded high mean mycelial growth inhibition (93.21%) at the lowest concentrations tested. This was followed by Carbendazim 50% WP (93.70%), Propiconazole 25% EC (93.45%), Tebuconazole 25% EC (90.49%), and Tricyclazole 45% + Hexaconazole 10% WG (90.74%). These fungicides exhibited consistent performance across concentrations and were significantly superior to the control in suppressing the growth of C. siamense.