In vitro Evaluation of Fungicides and Plant Extracts against Early Blight of Tomato Caused by Alternaria solani

Abstract

Early blight of tomato caused by Alternaria solani is an important disease that can reduce crop performance and fruit quality. This study evaluated the in vitro efficacy of six fungicidal treatments and four plant-derived treatments against A. solani using the poisoned food technique at two concentrations. Systemic fungicides were tested at 500 and 1000 ppm, whereas non-systemic and combination fungicides were tested at 1000 and 3000 ppm. Plant extracts were evaluated at 2500 and 5000 ppm. Mean colony diameter and percentage inhibition relative to the untreated control were used to compare treatment efficacy. Among the fungicidal treatments at the higher concentrations, carbendazim 12% + mancozeb 63% produced the greatest inhibition of mycelial growth (92.22%), followed by hexaconazole (91.11%) and mancozeb (90.00%). At the lower concentrations, hexaconazole showed the greatest inhibition (88.89%). Among the plant-derived treatments, Multineem, a neem oil-based EC formulation, showed the highest inhibition at both 5000 ppm (53.33%) and 2500 ppm (37.78%). Ginger rhizome extract ranked next at both concentrations, whereas eucalyptus leaf extract produced the lowest inhibition. Overall, the tested fungicides showed greater in vitro suppression of A. solani than the plant extracts. The results identify carbendazim + mancozeb, hexaconazole, mancozeb, and Multineem as treatments warranting further evaluation under field conditions before recommendations for early blight management are made.