Comparative analysis of nine fungicides in inhibiting the growth of Neopestalotiopsis sp. under in-vitro conditions

Abstract

Recently a severe disease outbreak caused by Neopestalotiopsis sp. on strawberries was reported from commercial cultivations in Sri Lanka. The symptoms began with reddening of the leaves progressing to necrosis. As the disease progressed, wilting and eventual death of the infected plants occurred along with the lesions on the roots and crowns. This research was conducted to evaluate the in vitro efficacy of nine commercial fungicides against the pathogen; Commercial fungicides including Topsin M (thiophanate – methyl 70%(w/w) WP), Captan (captan 50%(w/w) WP), Carbendazim (carbendazim 50%(w/w) WP), CarbrioTM top (metiram 55% + pyraclostrobin 5% WG), Mancozeb( mancozeb 80%(w/w)WP), Azoxystrobin (azoxystrobin250 g/l SC), Homai® (Thiophanate methyl 50% +Thiram 30% + Aditivos 20% (w/w) WP) , Daconil (chlorothalonil 82.5%), Ridomil Gold® SL( mancozeb 64% + metalaxyl 8%(w/w)WP) were tested against the pathogen. PDA plates amended with fungicides at concentration ranging from 0ppm to 2500ppm were prepared. Five mm diameter mycelial plugs of Neopestalotiopsis sp. pure culture were inoculated to each plate with triplicate for each treatment. Mycelial growth inhibition was determined 72 hours after inoculation. The effective concentration that inhibits mycelial growth by 50% was determined for each fungicide and statistical analysis for EC50 values was conducted. CabrioTM top, Ridomil Gold® SL, Daconil, Mancozeb, Homai® and Captan showed 100% inhibition against the fungus. EC50 values for Carbendazim, Topsin and Azoxystrobin were determined to be 2241.087±91.419 ppm, 418.663±11.20 ppm, and 471.958 + 10.891 ppm respectively. Based on in vitro assay CabrioTM top, Redomil Gold® SL, Daconil, Mancozeb, Homai® and Captan fungicides demonstrated higher efficacy in inhibiting the mycelial growth of Neopestalotiopsis sp. According to the one-way ANOVA, six out of nine fungicides; CabrioTM top, Ridomil Gold® SL, Daconil, Mancozeb, Homai® and Captan fungicides exhibited a significant inhibition of the Neopestaoloteopsis sp. However, field level experiments should be carried out to further validate results obtained in this in vitro study.