Characterization of Rhizoctonia solani causing Fruit rot of Strawberry (Fragaria x ananassa Duch.) in Wayanad and in vitro Evaluation of Fungicides, Organic preparations and Bioagents for its Management

Abstract

Strawberry, one of the most delicate, sweet and refreshing temperate fruit has grabbed the minds of several farmers and consumers all over the world. Several fungal diseases affect it. As part of the study, surveys were carried out in major strawberry growing parts of Kerala viz., Wayanad, Idukki, Malappuram and Thrissur. However, rotten fruits with dark and hard encrustations were collected only from Wayanad district during 2015-16. Pathogen was isolated by following the standard protocol and Koch’s postulates were proved. Upon culturing, the fungal isolate produced white mycelia turning brown on maturation with rapid growth. The hyphae were branched at right angles and did not produce spores. The pathogen was identified as Rhizoctonia solani based on cultural and morphological characters. In vitro evaluation was carried out with 9 fungicides and carbendazim 12% + mancozeb 63% , cymoxanil 8% + mancozeb 64% , propineb and Bordeaux mixture at all concentrations showed cent per cent inhibition. Copper hydroxide and difenoconazole inhibited the pathogen from 54.44 to 75 per cent and 58.88 to 70.55 per cent at 0.1, 0.15 and 0.2 and 0.05, 0.1 and 0.15, respectively. Copper oxychloride recorded less than 45 per cent inhibition, whereas carbendazim and potassium phosphonate were found to be least effective. Comparing the efficacy of organic preparations against Rhizoctonia, calphomil recorded highest inhibition of 55.33 to 63.88 per cent at different concentrations. Panchagavya and baking powder + vegetable oil mixture could inhibit the mycelial growth only by 23.33 to 25.50 per cent and 22.22 to 26 per cent, respectively. Whereas, neem oil was found to be least effective. Biocontrol agents were evaluated against the pathogen and Trichoderma asperellum could restrict growth of the pathogen by 66.67 per cent and Pseudomonas fluorescens by 33.33 per cent.