Status of dieback disease of mango in subtropical zone of Himachal Pradesh

摘要

Mango occupies a prominent position in fruit industry of India and has tremendous importance due to its nutritive value, taste, attractive fragrance and health promoting qualities. Thus it is recognized as one of the best fruits in the world market and is considered as the king of all fruits. Mango is the most important fruit grown in subtropical zone of Himachal Pradesh. It occupies an area of 41989 hectares and production of 31353 M.T. (Anonymous, 2018) but the productivity is low. The low productivity is due to diversity of associated disease problems. Mango can be attacked by a number of fungal and bacterial pathogens causing several diseases in all parts of the tree and all stages of life (Ploetz, 2004). Dieback disease is becoming severe in mango orchards of the subtropics of Himachal Pradesh. The symptoms of dieback disease include dieback of terminal shoots, leaf drooping and drying, browning of whole leaf followed by complete defoliation, discolouration and darkening of the bark, cracking,bark splitting and gummosis. Dieback is steadily gaining ground each year, spreading into new orchards and damaging by way of declining many such mango grooves. Mango plantations are increasing rapidly and the disease is posing a great threat to profitable cultivation of mango (Prakash and Srivastava, 1987). No studies have been undertaken to establish the status of dieback on mango trees grown in commercial mango orchards. The present studies were undertaken to determine the status of die back diseasein mango orchards of the area. The study was conducted in Nurpur and Indora areas of district Kangra. These areas were selected because they are the main mango growing areas in the state. To ascertain the actual status of dieback disease surveys were conducted for two consecutiveyears in commercial mango orcnards. ine orchards were randomly selected. In each orchard trees were carefully observed. The epidemiological parameters, the proportion (disease incidence) and intensity of symptoms (severity index) of dieback disease wereassessed. The disease incidence (DI) was determined from the proportion (%) of plants infected with dieback out of the total number of plants observed in the orchard according to following equation: The severity ratings were assigned based on a scale of1 to 5 (Ramos et al, 1997) according to followin gequation.