Ink spot
Drechslera iridis
What is Ink spot (Drechslera iridis) ?
Bipolaris iridis, also known as Drechslera iridis, is the fungus responsible for Ink spot disease. Symptoms include small, dark-brown spots on leaves, stems, and flowers, which enlarge and merge, leading to leaf collapse. Ink spot can be mistaken for Cladosporium leaf spot. Bulbs exhibit irregular ink-black stains on husks and small yellow dots or sunken black craters with raised margins. Severe disease occurs in plants left in the ground for 2 years. Mild and moist conditions favor disease development.
How does Ink spot (Drechslera iridis) occur?
Bipolaris iridis (Drechslera iridis) reproduces through spore formation and dissemination. Overwintering on infected debris and bulbs, the fungus produces spores within dark-brown spots on leaves, stems, and flowers. Mature spores are released and spread by air or water. Upon landing on susceptible plants, they initiate new infections, leading to ink spot disease. Disease development is favored by mild temperatures and moisture.
Symptoms
1 - Impact on Plant and Soil
• Drechslera iridis can cause various detrimental effects on plants, such as reduced photosynthesis and stunted growth. It weakens infected plants, leading to decreased flower production and compromised flower quality, which can negatively impact market value. • Additionally, there is a potential risk to soil health, including the spread of soilborne diseases and disruption of the soil microbial balance.
Solutions
1 - Cultural Control
• During the fall season, remove and destroy leaves that show signs of infection. • Maintain proper plant spacing to ensure good air circulation around the plants. • Rotate plantings, avoiding planting in the same location for consecutive years. • Divide plants frequently to prevent overcrowding and congestion.
2 - Fungicides
• The fungicides recommended for Ink spot disease control include Armada 50 WDG, Chipco 26019 FLO, Bonide Fung-onil Multi-purpose Fungicide, Daconil Weather Stik, Mancozeb-based products, Fore 80 WP, Protect DF, Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens, and Spectro 90 WDG. • It is important to follow the recommended application rates and instructions for each fungicide to ensure proper usage and maximize control efficacy.
