Evaluation of fungicide sensitivity in Colletotrichum gloeosporioides causing arecanut leaf spot disease

Abstract

Arecanut (Areca catechu L.) is an economically important plantation crop in India, but its productivity is increasingly threatened by leaf spot disease caused by Colletotrichum gloeosporioides. Effective disease management relies on identification of potent fungicides, particularly against virulent isolates. The present study evaluated the in vitro sensitivity of a highly pathogenic isolate (Shiralakoppa) to contact, systemic and combi-fungicides using poisoned food technique. Among the contact fungicides, Propineb (61.39% mean inhibition) was most effective, followed by Bordeaux mixture (49.44%), while other copper-based formulations recorded demonstrated minimal efficacy (Copper hydroxide 53.8% DF: 17.22%; Copper oxychloride 50% WP: 29.72%). Systemic fungicides exhibited significantly higher efficacy, with Tebuconazole (97.50%), Propiconazole (93.89%) and Carbendazim (89.17%) showing strong inhibition of mycelial growth. Strobilurins such as Azoxystrobin (70.83%) and Trifloxystrobin (84.17%) were moderately effective. Combi-fungicides performed best overall, with Mancozeb + Carbendazim (95.28%), Azoxystrobin + Tebuconazole (92.78%) and Zineb + Hexaconazole (89.72%) achieving near-complete inhibition at higher concentrations. The results highlight that triazoles, particularly Tebuconazole and Propiconazole and combi-products integrating systemic and contact fungicides, offer the most promising options for integrated management of C. gloeosporioides in arecanut and also demonstrate clear concentration-dependent responses for all fungicides, with combination products and systemic fungicides outperforming single-site contact fungicides. These findings provide a baseline for fungicide selection and resistance management strategies to control leaf spot disease under field conditions.