Field Evaluation of Fungicides for Management of Alternaria Blight in Rapeseed (Brassica rapa var. toria)

Abstract

Alternaria blight caused by Alternaria brassica and, A. brassicicola singly or by mixed infection is one of the most widespread and destructive disease of oilseed brassicas globally. In order to identify the effective and economic molecules of fungicides against Alternaria blight, a field trial was conducted during Rabi 2021-22 and 2022-23 at Nagaon, Assam in rapeseed (Brassica rapa L. var. toria). The trial was conducted with seven fungicides and replicated thrice (RBD) to assess the most effective fungicide in managing the disease. Among the different fungicides tested, the ready-mix formulation of tebuconazole 50% + trifloxystrobin 25% WG resulted in maximum reduction in disease severity both on leaves (54.1 %) and pods (55.7 %). Thus, this combo-formulation led to realization of the highest seed yield (1187 kg ha-1) with yield advantage of 78.5 % over check. The highest net monetary return (NR) of Rs. 39001 ha-1 with benefit-cost ratio (B:C) of 2.02 was received in the treatment, followed by azoxystrobin 23 % SC @ 1 ml l-1 with 46.1 % and 45.8 % reduction in disease incidence respectively on leaves and pods and yield increase of 54.8 %. Interestingly, when B:C ratio was calculated, azoxystrobin 23% SC recorded the highest B:C (2.31) with NR of Rs. 37959 ha-1.