Field Identification
Aggressive oomycete root and crown rots affecting avocado, citrus, tomato, pepper, raspberry, and landscape trees—often tied to prolonged wet crowns, heavy clay, or contaminated surface water. Aboveground symptoms mimic drought or salinity.
Dark necrotic lesions advancing up the crown; fine roots absent; outer xylem stains in cross-section on woody hosts. Zoospores swim to new infection sites in standing water.
How to Deal With It
Organic Control Methods
Copper hydroxide on crowns of woody plants where labeled; phosphorous acid (phosphite) trunk injections or foliar/crown sprays on some crops as a systemic trigger of host defenses—follow organic certification rules.
Compost teas and Trichoderma drenches show variable suppression; combine with cultural fixes or you are rearranging deck chairs.
Plant on mounds; redirect runoff; use clean mulch away from trunks; graft onto tolerant rootstocks; avoid over-irrigation; choose well-drained sites.
Remove soil from infected crowns carefully, air-dry briefly where appropriate, then replace with clean mulch—paired with irrigation changes.
Buy certified clean nursery stock; test irrigation sources; do not propagate from known-positive blocks.
Let Nature Handle It
Natural Enemies
- Trichoderma asperellum
- Streptomyces spp.
- Competitive Saprophytes