Survey, Occurrence of Major Onion Diseases and Management of Twister Disease of Onion (Allium cepa L.)

Abstract

Purple blotch of onion caused by the fungus Alternaria porri is a serious disease in kharif season and more yield losses in onion growing areas of Maharashtra. A survey was conducted to assess disease intensity of major diseases in onion growing area in Nashik district during kharif 2020 and 2021 During the survey, small whitish, leaf curling, twisting, chlorosis of leaves, elongation of neck and cylindrical bulb such symptoms of twister disease were observed more severe than purple blotch on onion in kharif 2020. The per cent disease severity ranged from 17.28 to 45.83 per cent and 8.00 to 23.00 per cent in purple blotch of onion and 20.17 to 54.59 per cent and 12.00 to 35.00 per cent twister disease of onion during kharif 2020 and 2021, respectively. The diseased samples were utilized for isolation of pathogen. After isolation and morphological   study, it is indicated that twister disease of onion was complex of pathogen caused by Colletotrichum gloeosporioides,  Fusarium sp. and nematode. Due to climate change, from the survey concluded that twister disease was found more serious and threatening disease than purple blotch of onion during kharif 2020 and 2021.  Considering the yield losses caused by twister disease of onion, the investigation was planned for management of twister disease during kharif 21. The combine application of Trichoderma drenching @ 10 g/l along with two alternate sprays of each Tebuconazole 25.9 EC @ 1 ml/l or Azoxystrobin 23 SC@ 1 ml/l recorded lowest PDI of twister disease (14.33%) of onion than the control treatment (49.11%) and which was found effective maximum per cent disease over control (70.82%) for management of twister disease of onion.