Abstract:
Betelvine (Piper betle L.) is an important cash crop grown throughout the year
in Bangladesh. Isolation and identification of the causal organism, pathogenicity
test and development of management practices against Pestalotia sp. were the
main purposes of the investigation. The in vitro experiments were conducted at
MS Laboratory, Department of Plant Pathology and the field experiment was
conducted in the Central Farm of Sher-e-Bangla Agricultural University (SAU),
Dhaka-1207. Pestalotia sp., the causal organism that caused leaf spot of
betelvine is a new record in Bangladesh. A survey was conducted in four upazilas
viz. Kaligonj, Debhata, Shymnagar under Satkhira district and Debidwar upazila
under Cumilla district to investigate the prevalence of Pestalotia sp. causing
pestalotia leaf spot of betelvine. The survey study revealed that the disease
incidence of pestalotia leaf spot of betelvine ranged from 8.70% to 42.77%. The
maximum 42.77% disease incidence was recorded in Kaligonj, Satkhira and the
minimum 8.70% disease incidence was recorded in Debidwar, Cumilla. The
maximum 13.66% disease severity was recorded in Shymnagar, Satkhira where
minimum 2.65% disease severity was recorded in Debidwar, Cumilla. The
organism isolated from the diseased leaf was identified as Pestalotia sp. based
on its characteristics (CMI Description no. 515) and the pathogenicity was
confirmed by following Koch’s Postulates. In the disease mitigation study, four
chemical fungicides viz. Autostin 50 WDG, Tilt 250 EC, Goldton 50 WP and
Dithane M-45, four plant extracts viz. Garlic clove extract, Ginger Rhizome
extract, Onion bulb extract and leaf extract were evaluated. The fungicide Tilt
250 EC and Autostin 50 WDG @500ppm concentration completely (100%)
inhibit the mycelial growth of the pathogen in in vitro. In the field condition,
maximum 81.74% reduction of disease severity over control was recorded in
case of Tilt 250EC, followed by Autostin 50 WDG (67.83%). In case of plant
extracts, Garlic clove extract resulted the highest reduction 86.68% of mycelial
growth at 1:1 concentration in in vitro and the reduction of disease severity was
60.87% over control in field experiment. In case of 1:2 concentration, the
reduction of mycelial growth was less than 1:1 concentration.
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
IN
PLANT PATHOLOGY
