Abstract:
An epidemiological survey on the incidence and severity of purple
blotch of onion was conducted during ·onion growing seasons of the year
2007-08, 2008-09 and 2009-10 (Winter- September to March) in the major
onion growing areas viz. Vasanchar (Faridpur), Jitka (Manikgonj), Sayedpur
(Comilla), Nandina (Jamalpur), Kesobpur (Jessore), BARI (Gazipur), SAU
campus (Dhaka), Hathazari (Chittagong), Dhamrai (Dhaka), Taherpur
(Rajsbahi) of the country, Data were collected on % Plant infection, % Leaf
infection, % LAD ( Leaf Area Diseased ), % SAD (Stalk Area Diseased),
Soil pH, Soil temperature, Soil moisture, Air temperature and Air humidity
(% RH). The disease incidence and severity of purple blotch of onion varied
with locations, and environmental factors. The plant infection and leaf
infection ranged from 87 % - 36 % and 62 % - 20 %, respectively while the
percent leaf area diseased (% LAD) and percent stalk area diseased (% SAD)
ranged from 36.67 % - '9.00 % and 39.00 % - 11.00 %, respectively. The
highest disease incidence and severity during the consecutive 3 growing
seasons of the year 2007-08,2008-09 and 2009-10 was recorded at Sayedpur
(Comilla) where average air temperature, air humidity and pH were 24.08oC,
75.17% and 4.72 respectively. The lowest incidence and severity was
recorded at BARI (Gazipur) where average air temperature, air humidity and
pH were 23.990C, 85.44% and 5.30 respectively. Soil pH (4.6 -5.17), air
temperature (23°C) and air humidity (75 % ± 2) had influential effect on the
incidence;3l1d severity of purple blotch of onion.
Description:
A Thesis
Submitted to the Faculty of Agriculture,
Sher-e-Bangla Agricultural University, Dhaka
in Partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE (MS)
IN
PLANT PATHOLOGY
