MANAGEMENT OF PURPLE BLOTCH OF ONION IN SUB–TROPICAL ZONE OF HIMACHAL PRADESH
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Date
2020-10-19
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COLLEGE OF HORTICULTURE AND FORESTRY, DR Y S P UHF, NERI, HAMIRPUR
Abstract
Purple blotch caused by Alternaria porri (Ellis) Cifferi is one of the major disease in onion growing areas.
In the present investigation, it was found that disease occurred in moderate to severe form with 25.00 to
84.00 per cent incidence and 13.33 to 66.67 per cent disease index in different localities of Hamirpur,
Bilaspur, Una and Kangra districts of Himachal Pradesh. 72 hours of incubation period was observed by
spray inoculation of the pathogen. Among eight different systemic fungicides, complete mycelial
inhibition was observed by azoxystrobin+difenoconazole, metiram+pyraclostrobin and
trifloxystrobin+tebuconazole. Foliar sprays of trifloxystrobin+tebuconazole at 200 ppm and
azoxystrobin+difenoconazole at 50 ppm was found most effective for the management of purple blotch of
onion in pot experiment. Under field conditions, three foliar sprays of trifloxystrobin+tebuconazole at 200
ppm and azoxystrobin+difenoconazole at 50 ppm concentration resulted in reduction in disease incidence
up to 85.95 and 82.61 per cent and disease index up to 91.03 and 90.76 per cent, respectively with
maximum bulb yield of 1.87 and 1.63 kg/plot, respectively. Among aqueous extracts, maximum mycelial
inhibition of 63.65 per cent was observed by using extract of Datura stramonium at 50 per cent
concentration. Cow urine alone resulted in complete inhibition in mycelial growth of pathogen. While in
cow urine extracts, maximum mycelial inhibition of 84.52 and 68.09 per cent was observed with extract of
Murraya koenigii and D. stramonium at 40 per cent concentration. In pot experiments aqueous extract of
Datura stramonium was superior among other extracts and resulted in reduction in disease incidence up to
44.45 per cent and disease index up to 57.77 per cent. Application of cow urine alone was best in
reduction of disease incidence up to 91.33 per cent and reduction in disease index upto 93.57 per cent.
While in cow urine extract of M. koenigii and D. stramonium are effective for disease management.
Among eight different abiotic resistance inducers, salicylic acid at 20 mM and 10 mM was found most
effective for the management of purple blotch of onion in pot experiment.