Incidence and severity of leaf, panicle and fruit blights of litchi caused by Alternaria alternata

Abstract

Leaf, panicle and fruit blights of litchi (Litchi chinensis Sonn.) caused by Alternaria alternata (Fr.) Keissler is a recent and economically important disease of litchi. The incidence and severity of this disease was assessed during 2012–2017 in continuous monitoring of the disease at National Research Centre on Litchi, Muzaffarpur and farmers’ orchards in Bihar. The results revealed an average incidence of leaf blight from 7.1 to 82.6% on nursery plants while percent disease severity index (PDI) was 43.3–71.2 during 2012–2017. Disease incidence of panicle blight (on tree basis) in different orchards during 2014–2016 was from 6.3 to 77.1% in cv. ‘Shahi’ and 17.0–58.9% in cv. ‘China’. However, the maximum number of trees recorded less than 20% blighted panicles. Incidence of fruit blight in cv. ‘China’ ranged from 6.6 to 17.3%. The analysis of prevailing weather conditions revealed that a temperature of about 28–30 °C and humidity 60–85% were congenial for development of blight disease on panicles and fruits. A. alternata is an opportunistic pathogen on numerous hosts. Due to its large spore and dark pigment, this is resistant to UV radiation and spores can float in the air enabling long distance dispersal. Litchi being cultivated over a large area in Bihar and adjoining states of India, the pathogen has the potential to spread causing heavy yield losses.