Efficacy and physical modes of EBI and strobilurin fungicides in managing French bean rust ( Uromyces appendiculatus )

Recently available EBI and Strobilurin fungicides were evaluated against Uromyces appendiculatus (Pers.) Unger, the causal agent of French bean rust under laboratory, semi-controlled and in vivo conditions during 2015 and 2016 crop seasons. Tebuconazole + trifloxystrobin (100 ppm), azoxystrobin (100 ppm), azoxystrobin + difenconazole (100 ppm), propiconazole + difenconazole (100 ppm), mancozeb (250 ppm) and chlorothalonil (500 ppm) caused complete inhibition of urediniospore germination under laboratory conditions. Azoxystrobin alone and its combination with difenconazole, tebuconazole, tebuconazole + trifloxystrobin provided excellent protective activity under field conditions, boosted pod yields as well as improved horticultural traits like pod length, pod diameter, pod weight and leaf area. In studies of physical modes of fungicides, mancozeb (2500 ppm), azadirachtin (50,000 ppm) provided protective activity up to 3 and 1 day, respectively and were observed as weak protectant while 2 EBI’s viz., tebuconazole (1000 ppm), hexaconazole (1000 ppm) and a strobilurin, azoxystrobin (1000 ppm) exhibited good protective activity up to 5 days under semi-controlled conditions. EBI fungicides (tebuconazole and hexaconazole) showed magnificent curative (post infection) activity, i.e. up to 3 days while in strobilurin (azoxystrobin) and mancozeb it was only 1 and < 1 day, respectively.