Source: TH
Subject: Ecology
Context: Premier government institutes in Karnataka are completing the first year of a three-year field demonstration project this June to manage leaf spot disease (LSD) in arecanut plantations.
About Leaf Spot Disease (LSD):
What it is?
- Leaf spot disease is a pathological condition that weakens trees and shrubs by interrupting photosynthesis, the process by which plants produce energy. While often a minor stressor, it can become a critical threat if it persists over several growing seasons.
Vector/Spread: Pathogens are primarily spread by wind or splashing rain and irrigation, which carry spores to susceptible plant tissue.
Causes: Most leaf spot diseases are caused by fungi, though some are triggered by bacteria or other pathogens. They thrive in environments with high humidity or water remaining on leaves for 12 to 24 hours.
Key Features and Identification:
- Appearance: Spots can be angular or rounded, raised or sunken, with smooth or fringed edges. Colors range from yellow and orange-red to brown or black.
- Infection Pattern: Symptoms usually appear first on lower and inner branches where humidity is higher.
- Age Indicators: Smaller spots typically represent younger infections, while larger spots indicate older ones where fungal spores may be visible at the center.
- Survival: Pathogens can survive the winter in infected leaf debris, buds, or young twigs.
Treatment and Management:
Managing LSD requires a package of practices rather than isolated chemical treatments.
- Sanitation: Raking and destroying fallen leaves before snowfall prevents the pathogen from re-infecting plants in the next season.
- Cultural Practices: Proper drainage of excess rainwater, pruning to improve air circulation, and spacing plants to avoid overcrowding.
- Soil Health: Liming acidic soils based on soil tests and balanced application of nutrients, micronutrients, and neem cake.
- Chemical/Biological Control:
- Application of Trichoderma to reduce soil-borne infection.
- Spraying Bordeaux mixture during the monsoon.
- Targeted use of fungicides like Propiconazole, Tebuconazole, or Propineb following the removal of infected fronds.
