INVESTIGATION ON PESTALOTIA LEAF SPOT OF BETELVINE (Piper betle L.) AND ITS MANAGEMENT

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.