Avocado Root Rot Disease Management

Since no definitive measures have yet been found to control the disease, an integrated approach to managing the root rot disease has been found to be most effective. This approach includes root rot prevention, avocado grove cultural management practices and chemical treatment.

Avocado grove cultural management practices to help prevent root rot disease

• Provide favorable soil conditions — avocado roots die if continuously wet, so soils need to be loose and free draining.
• Use certified disease-free nursery stock.
• Plant resistant rootstocks.
• Prevent soil or water movement from infested areas.
• Avocado trees do not search for water and their roots are only in the top six inches of soil under the tree canopy. Topsoil tends to dry out, so irrigation is necessary to keep the soil moist and the tree healthy. Too much water can drown the roots, so careful water requirements calculations must be made. The California Irrigation Management Information System (CIMIS) is a great resource to calculate daily water use.
• Apply gypsum and mulch.
• Provide appropriate nutrition.To determine the exact amounts and times of applying fertilizers you must monitor your grove, take notes and use a specialist who will perform soil, leaf and water tests. The specialist will determine amounts based on fruit load, cropping history, growth cycles, soil/leaf/water tests and existing regulations.
• Rotate crops.

Chemical controls for root rot disease prevention

• Systemic fungicides.
• Fosetyl-Al (Aliette®) or potassium phosphonate can be applied as soil drench, foliar spray, trunk paint, trunk injection (buffered) or with irrigation water trunk injection (buffered solution).
• Metalaxyl (Ridomil®) can be applied as granular, a drench or with irrigation water.