Bio-efficacy evaluation of Chlorothalonil 40% w/w + Difenoconfazole 4% w/w SC against apple diseases

Abstract

Uttarakhand hills are best suited for production of a variety of fruit crops due to favorable agro-climatic conditions with apple being the most important temperate fruit grown in the region. Apple is the prime fruit of Uttarakhand and plays a major role in horticultural development and in improving economic status of the growers. The major diseases of apple crop in hill and mountain regions are scab [Venturia inaequalis (Cke.) Wint], premature leaf fall (Marssonina coronaria and Alternaria mali) and powdery mildew [Podosphaera leucotricha (Ellis and Everhart)] etc. These diseases have already plagued apple cultivation in Uttarakhand hills which happen to be the 3rd largest apple growing state of the country. Hence, to manage these diseases, Chlorothalonil 40% w/w + Difenoconazole 4% w/w SC at different dosages along with standard checks viz., Chlorothalonil 75% WP, Difenoconazole 25% EC, Propineb 70% WP, Sulphur 80 WG and Metiram 55% + Pyraclostrobin 5% WG at recommended doses were evaluated for bio-efficacy and phytotoxicity against apple scab, premature leaf fall and powdery mildew diseases at Harsil (District- Uttarkashi, Uttarakhand) during 2017 and 2018. The data analysis of two crop seasons (2017 & 2018) showed that all the treatments differed significantly with respect to per cent disease severity and per cent disease reduction over control for all the diseases studied. However, the treatment T4 (Chlorothalonil 40% + Difenoconazle 4% w/w SC @ 900 ml/ha) was found most effective followed by treatment T3 (Chlorothalonil 40% + Difenoconazole 4% w/w SC @ 800ml/ha) for all the diseases studied under present materials and conditions at Harshil location during 2017 and 2018. The data of two crop seasons indicated that maximum yield (98.83q/ha in 2017 and 95.20 q/ha in 2018) was recorded when the crop was sprayed with Chlorothalonil 40% + Difenoconazle 4% w/w SC @ 900 ml/ha followed by Chlorothalonil 40% + Difenoconazole 4% w/w SC @ 800ml/ha with 95.44 q/ha in 2017 and 94.55q/ha in 2018, respectively. For phytotoxicity studies, Chlorothalonil 40% + Difenoconazle 4% w/w SC @ 900 & 1800 ml/ha did not show any phytotoxic effects viz., yellowing, necrosis, chlorosis, epinasty, hyponasty and stunting on apple crop.