For home growers with avocado trees, a fungal root-rot disease may wreak havoc on your trees. To avoid loss of crops and the cosmetic damage of your home landscape, familiarize yourself with the red flags for root rot as well as ways to avoid invasion by fungal pathogens and a reliable management plan.
Give your avocado trees the care they need to increase potential for avoiding fungal infection. Vigorous plants are less likely to suffer from disease than stressed plants in poor health. Grow subtropical avocado trees in full sunlight for successful fruit development. Avocado trees need extremely well-drained soil as poor drainage may cause extreme damage like malnutrition or plant death, according to the University of Florida IFAS Extension. Additionally, wet sites provide ideal environments for fungi germination.
Root rot is the most widespread, problematic avocado disease throughout the world, according to the University of California IPM Online. Root rot is caused by the fungus Phytophthora cinnamomi. The main factor contributing to infection is poorly drained soil of avocado trees. With its sporadic spreading habit, this pathogen is easily transferred, particularly in cases of poor sanitation and growing practices.
Avocado root rot affects all parts of the avocado tree. Fruit crops may appear normal in yield or may greatly diminish. Leaves appear yellow to light green with brown tips. Root rot typically causes defoliation and the cessation of new leaf growth, according to the University of California IPM online. Branch dieback occurs and smaller roots rot and die. The entire avocado tree suffers from severe decline and, particularly if left untreated, dies.
Natural control methods may keep your trees from experiencing avocado root rot. Always sanitize pruning tools and any other equipment after use on one tree to prevent spreading disease to the next. If only one tree in your landscape is infected, isolate the tree with a barrier to prevents water runoff from reaching other trees, advises the University of California IPM Online. Additionally, add a layer of up to 6 inches of mulch made from organic material to the soil surrounding your tree, but not pressed against the trunk. Mulch keeps friendly microorganisms in the soil that help fight infection.
Phosphite fungicides offer an effective chemical control for avocado root rot. Though you may spray foliage, applying fungicides to soil is the most effective method. For trees that bear fruit, apply a fungicide with an active ingredient of phosphorus acid or mefonaxam. For trees that do not bear fruit, apply aluminum tris phosphonate, according to the University of California IPM Online.