White rot
Sclerotium cepivorum
What is White rot (Sclerotium cepivorum)?
White rot, caused by the fungus Sclerotium cepivorum (Stromatinia cepivora), affects Allium species like onions, leeks, and garlic. Infected plants show yellowing, leaf dieback, and wilting from the base, while bulbs decay with a semi-watery rot. Roots rot, leading to easy uprooting. Infected plant material may display small fluffy white mycelium and pinhead-sized black sclerotia. The disease thrives in cool, moist soil conditions (60° to 65°F) and poses a significant threat to crop health and yield.
How does White rot (Sclerotium cepivorum) occur?
Sclerotium cepivorum, reproduces through the production and dissemination of sclerotia. These small, dormant structures are capable of surviving in the soil for extended periods, even in the absence of a host plant. Sclerotia germinates when stimulated by Allium root exudates, initiating the formation of fungal mycelium. The mycelium invades plant tissues, leading to the development of symptoms. As the disease progresses, new sclerotia are formed on the mycelial mat, contributing to the spread and persistence of the pathogen in the soil.
Symptoms
1 - Plants Health
White rot significantly reduces crop yields, weakens plants, making them prone to other diseases and pests. Infected bulbs have reduced storability, shorter shelf life, and increased post-harvest losses, contributing to a decline in plant health and productivity.
2 - Impacts on Soil
• The sclerotia of Sclerotium cepivorum can persist in the soil for up to 20 years, resulting in a long-lasting risk of disease. • Build-up of pathogen inoculum, increasing the likelihood of disease outbreaks. It reduced soil fertility and productivity due to crop losses. • Altered soil microbial communities and nutrient cycling affect overall soil health and availability.
Solutions
1 - Prevention Measures
• Use disease-free planting material from reputable sources. • Avoid introducing infected transplants, sets, or garlic cloves. • Implement a long-term rotation schedule, avoiding consecutive Allium crops in the same field. • Remove and destroy infected plant debris to minimize the spread of the fungus. • Apply fungicides preventively before disease development or at the first sign of symptoms. • Ensure thorough coverage of plants, especially the base of bulbs and surrounding soil.
2 - Fungicides Application
• Some commonly used fungicides for disease control in various crops include Captan (Captan 50 WP, Captan 80 WDG), Mancozeb (Dithane M-45, Manzate Pro-Stick), Thiophanate-methyl (Topsin M, T-Methyl SPC 50 WSB), Myclobutanil (Rally 40W, Systhane), Chlorothalonil (Bravo Weather Stik, Daconil), Azoxystrobin (Quadris, Amistar), Propiconazole (Tilt, Banner Maxx), and Cyprodinil + Fludioxonil (Switch, Pristine). • It's important to consult with local agricultural experts or authorities for specific recommendations and availability in your region. Always follow label instructions for proper and safe use of fungicides.
