Armillaria root rot (Oak root fungus)
Armillaria mellea
Also Known As - Honey fungus,Oak root fungus (Armillaria root rot),Armillaria root rot,Wood decay (general)What is Armillaria root rot (Armillaria mellea)?
Armillaria root rot, caused by Armillaria fungi, affects various plants like trees, palms, ferns, and more. Also known as "oak root fungus," it commonly occurs in California's home gardens, parks, vineyards, and tree crops. Infected plants exhibit symptoms such as decline, wilting leaves, rapid death, bleeding, defoliation, twig dieback, thinning, and flat cankers on the trunk. Armillaria root rot is indicated by the presence of light brown mushrooms, mycelial fans, and black rhizomorphs.
How does Armillaria root rot (Armillaria mellea) occur?
Armillaria root rot spreads through root-to-root contact between plants and by releasing spores through mushrooms. The fungus reproduces vegetatively when roots come into contact with each other. It also reproduces sexually by releasing spores that can colonize dead stumps or woody debris nearby. To establish new growth, two spores with half the parent's genetic material must fuse in the same wood. This process leads to the mushroom formation and spore release for further dissemination.
Symptoms
1 - Effects on plants
The disease can harm the root system of plants, causing decay and rot, leading to reduced root function, poor nutrient uptake, and stunted growth.
2 - Effects on soil
The fungus can alter the microbial composition of the soil, leading to decreased soil fertility, increased soil-borne pathogens, and soil compaction.
3 - Effects on the environment
The disease can negatively impact forest ecosystems by increasing susceptibility to other pests and diseases, causing trees to fall, and disrupting the natural nutrient cycle and energy flow.
Solutions
1 - Plant selection and good cultural practices
• Choose resistant plant species or cultivars that are less susceptible to Armillaria infection. • Ensure proper planting techniques, including proper soil drainage and avoid planting too deeply. • Maintain plant health through proper watering, fertilization, and pruning. • Avoid overwatering or creating waterlogged conditions.
2 - Soil management and removal of infected material
• Improve soil drainage by incorporating organic matter, such as compost, and avoid excessive irrigation. • Promptly remove and destroy infected plants, roots, and stumps to prevent the spread of the fungus.
3 - Chemical Control
• Here are a few fungicides commonly used for controlling Armillaria root rot: phosphite-based fungicides (e.g., potassium phosphite), thiophanate-methyl, metalaxyl, propiconazole, and fluazinam. These fungicides can be effective in managing the disease, • It is important to follow label instructions and consult with professionals for specific recommendations.
