TITLE:
In-Vivo Management of Purple Blotch of Onion Caused by Alternaria porri (Ellis) Cif. through Fungicides
AUTHORS:
Md. Mozidul Islam, Fatema Begum, Nazmoon Nahar, U. A. Habiba, K. M. Fakruzzaman
KEYWORDS:
Purple Blotch, Alternaria porri, Fungicides, PDI, Yield
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.11 No.11,
November
30,
2020
ABSTRACT: An experiment was carried out to study the outcome
of environmental factors (Temperature, Relative Humidity, Rainfall) and management of the purple
blotch disease of onion using five treatments (Rovral + Ridoil gold with
3,4,5,6 sprays and control). The Taherpuri variety was used during the
2015-2016 cropping seasons at BARI, Gazipur, Bangladesh. In the experiment, the
purple blotch disease surfaced at the end of January 2016 and was severe in late February to March (PDI
76.12%) due to temperature and RH above 24°C and 95%, respectively. As for the chemical control, the PDI for the
treatments ranged from 50.66% to 83.33%. Significantly higher stem height was recorded by T4 (68.06 cm), where six sprays of Rovral + Ridomil were applied. The minimum stem
height was recorded in T5 (59.23 cm). The maximum stem number per
hill was recorded in T4 (2.30) numerically but differed
significantly with T5 (2.00), where fungicides were not applied. The
maximum lesion area was measured in T5 (25.26 mm2).
Regarding PDI (Percent disease index), there was a significant difference among
the treatments. The PDI value on purple blotch of onion ranged from 34.00 to
83.33. The lowest PDI was assessed in T4 (34.00). Statistical
analysis revealed that a significant decrease of PDI on purple blotch was
recorded under treatments of T1, T2, T3, and T4 (39.20%, 45.60%, 49.59%, and 59.19%) on
controlling the disease and giving the optimum yield but all of them
significantly differed with T5 (83.33%) where no fungicides were
sprayed.