Choanephora pod rot of cowpea and its ecofriendly management

Abstract

The study entitled “Choanephora pod rot of cowpea and its ecofriendly management” was undertaken in the Department of Plant Pathology, College of Agriculture, Vellayani during 2013-2015 with the objective to study the symtomatology, etiology and to develop an ecofriendly management strategy for Choanephora pod rot of cowpea. The pathogen causing the pod rot of cowpea was isolated from the diseased pods, leaves, peduncle, stem and flowers. Pathogenicity was proven following Koch’s postulates, virulence rating was done and the C3 isolate obtained from cowpea pods were found to be the most virulent isolate. Based on cultural and morphological characters, the pathogen was identified as the Choanephora cucurbitarum (Berk. &Ravenel) Thaxt., which was further confirmed by ITS sequencing. The study revealed that the C. cucurbitarum had wide host range encompassing other vegetable crops such as bhindi, cucurbits, chilli, amaranthus and brinjal. Natural incidence of the disease was not observed on any weeds in and around the cowpea fields. However, on artificial inoculation of the pathogen, the spreading hogweed (Boerhaavia diffusa L. Noms. Cons) took up infection. The dual culture technique to study the antagonism of the saprophytic mycoflora isolated from the rhizosphere and fructosphere through serial dilution and plating indicated that Trichoderma virens and Pseudomonas fluorescens exhibited 79.50% and 55% percentage inhibition of the pathogen. The effectiveness of organic preparations such as panchagavya, jeevamruth, fish amino acid, vermiwash and compost tea was tested at different concentrations by poisoned food technique. Amendment of media was also done with autoclaved and filtered organic preparations. Vermiwash at 2.5%, 5% and 10% filtered as well as incorporated to media as such, significantly suppressed C.cucurbitarum. Jeevamruth (10%) and Panchagavya (10%) gave complete inhibition of the pathogen. Panchagavya (10%) incorporated after filtration and autoclaving also gave 100% and 94.4% suppression of the pathogen respectively. The application of effective dose of organic preparations on excised pods showed that panchagavya (10%) caused maximum suppression of pod rot (60.64%). Among the biocontrol agents, the selected bacterial antagonist i.e., P. fluorescens showed complete suppression of the disease when applied on the excised pods. A pot culture study was conducted to evaluate the efficiency of organic preparations, biocontrol agents and fungicides. The maximum disease suppression of 99.72% was observed in plants sprayed with copper hydroxide. The organic preparation, fish amino acid suppressed the disease to 87.33%. Application of effective biocontrol agent T. virens yielded 75.27% suppression of pod rot. The ecofriendly management of the disease can be achieved by application of fish amino acid (10%) or T. virens (106cfu/ml) or fungicides such as copper hydroxide (0.2%), mancozeb (0.3%) and propiconazole (0.1%) during the pod formation stage.