IN-VITROEVALUATION OF FUNGICIDES SENSITIVITY OF TOMATO LEAF BLIGHT PATHOGENS ISOLATES Alternariasolani and Phytophthorainfestans

Abstract

Tomato early and late blight diseases caused by Alternaria solani(Ellis & Martin) Sorauer and Phytophthora infestansrespectively hinder tomato production globally. Use of fungicides in management of blight diseases has become a priority among farmers. However, indiscriminate or use of sub lethal doses negate disease management efforts. Despites the knowledge of possible occurrence of fungicide insensitive phyto-pathogens, farmers has continued using fungicides without periodic evaluation of their effectiveness. This study was carried out to evaluate an in-vitro sensitivity of tomato leaf blight pathogens (Alternaria solaniand Phytophthora infestans) against selected fungicides mostly used by tomato farmers along River Ruguti in Tharaka Nithi County in Kenya.Fungicides evaluated included, Mancozeb (640 g kg-1 ) + Metalaxyl (40 g kg-1 ), mancozeb 640 g/kg + metalaxyl 80 g/kg, Mancozeb, Propineb700 g/kg + Cymoxanil 60g/kg, Carbendazim and Triticonazole at different concentration (25%, 50% and 75%). Poison food method was used for evaluation. Complete Randomise design was used for the experiment. Per cent data on mycelia growth inhibition by various fungicides at different concentration were analysed using General Linear Model (α=.05) and significant means separated using Least significant difference (LSD) in Scientific Analysis System version 9.4. All the tested fungicides significantly (P≤ 0.05) inhibited the mycelial growth of tested pathogen. However, among tested fungicides, Carbendazim (89.83%) and Propineb700g/kg +Cymoxanil 60g/kg were superior over other fungicides with Carbendazim being the least. Mycelia growth inhibition increased with an increase in fungicide concentration. Mycelia growth inhibition of Alternaria solaniwas 81.78% as compared to Phytophthora infestans at 69.78%.