In Vitro Screening of Fungicides for Controlling Leaf Spot Disease of Marigold Caused by Alternaria alternata

This study was conducted to evaluate the in vitro efficacy of various chemical fungicides against marigold leaf spot caused by Alternaria alternata. Disease incidence was recorded across multiple locations in the Hyderabad district of Sindh, with the highest occurrence observed in Ghangra Mori (35%) and the lowest in Hosri (15%). Other locations recorded incidence rates of 30% in Tando Hyder, 25% in Rahooki, and 20% in Moosa Khatyan. Among the tested fungicides, Nativo demonstrated the highest inhibitory effect on A. alternata, with colony growth reduced to 43 mm, 25.5 mm, and 18.5 mm at concentrations of 100, 200, and 400 ppm, respectively. Aliette, Carbendazim, and Mancozeb showed moderate efficacy Aliette: 52 mm, 31.5 mm, and 21 mm at 100, 200, and 400 ppm, respectively. Carbendazim: 52.5 mm, 29.5 mm, and 21 mm at the same concentrations. Mancozeb: 51 mm, 28.5 mm, and 20 mm at respective concentrations. At 400 ppm, Nativo exhibited the greatest inhibition of fungal growth, followed by Mancozeb, Carbendazim, and Aliette. In contrast, the control treatment recorded fungal growth of 90 mm. Additionally, plant-based treatments, particularly neem extract at a 6% concentration, significantly suppressed colony growth of A. alternata, indicating its potential as an eco-friendly alternative. Overall, Nativo at 400 ppm was identified as the most effective chemical fungicide for managing marigold leaf spot, while neem extract shows promise as a sustainable control measure