Damping off and seed rots
Thielaviopsis spp.
What is Damping off, seed and root rot (Thielaviopsis basicola)?
Damping off and seed rot caused by Thielaviopsis spp. are plant diseases affecting seedlings and young plants. Thielaviopsis is a soil-borne fungal genus that causes root rot in crops like cotton, tobacco, and vegetables. Damping off refers to seedlings collapsing and dying near the soil surface during germination or after emergence. Symptoms include blackened roots, lower hypocotyls, and dark green cotyledons and leaves. The disease is widespread in warm climates.
How does Damping off, seed and rot (Thielaviopsis basicola) occur?
It reproduces through different means. These fungi can produce spores, mycelium, or survival structures like sclerotia that can persist in the soil. The pathogens can be introduced into the soil through infected seeds, plant debris, or contaminated soil. They require favorable conditions such as high humidity, excessive moisture, and cool temperatures to infect plant roots and cause disease. Infection can occur during germination, seedling emergence, or later stages of plant growth.
Symptoms
1 - Effects on Plants
• Root rots can hinder root development, leading to stunted growth and reduced plant vigor. Infected plants may experience wilting and drooping of leaves due to root damage and impaired water uptake. • Severe infections can result in decreased crop yield or even plant death, leading to economic losses. • It can also impact the diversity and abundance of plant species in affected areas.
2 - Effects on Soil
• It contributes to the degradation of soil health and fertility, as infected roots decompose, and nutrient cycling is disrupted. • These pathogens can persist in the soil, leading to future infections and it can disrupt the natural balance of beneficial soil microorganisms, affecting soil ecology.
Solutions
1 - Prevention
• Consider using fungicidal seed treatments to protect seeds from fungal infections. • Remove and destroy infected plant debris to minimize the source of infection. • Avoid planting susceptible crops in the same location to reduce the buildup of fungal pathogens in the soil. • Ensure planting beds and containers have adequate drainage to prevent waterlogging. • Maintain good soil health through organic matter amendments, proper irrigation, and balanced nutrient management.
2 - Cultural Practices
• Wait to plant until soil temperatures are optimal for the specific crop, as cooler soil temperatures can promote disease development. • Use cultivars bred to be resistant or tolerant to specific root rot pathogens. • Avoid over-irrigation and ensure proper watering practices to prevent excess moisture that favors pathogen growth. • Manage weeds, as they can serve as hosts for pathogens. • Monitor plants for early signs of root rot to allow for prompt intervention.
3 - Chemical Control
• Some commonly used fungicides for controlling pathogens include Mefenoxam (Ridomil Gold SL), Fluopicolide (Presidio), Thiophanate-methyl (Topsin-M WSB), Azoxystrobin (Quadris) and Metalaxyl (Acquire), for various root rot pathogens. • Always follow label instructions for proper application rates and consult local experts for specific recommendations.
