Root rot can lead to the loss of crops and severe decline of your orange trees. Though particular fungal pathogens are directly responsible for the decaying of your orange tree's root system, other factors heavily contribute to fungal infection. Employ appropriate daily care to avoid losing the pleasing fragrance and edible fruit you enjoy in your home landscape.
A major cause of root rot in orange trees is poor care. Factors like inadequate sunlight and waterlogged or excessively dry soil put stress on trees and make them more vulnerable to infection. Grow orange trees in areas that provide full sunlight for proper fruit development and tree growth, according to the Texas Cooperative Extension. Orange trees thrive in moist, extremely well-drained soil.
Phytophthora root rot disease is the direct cause of root rot in orange trees. Fungal pathogens of the Phytophthora species, including Phytophthora citrophthora and Phytophthora parasitica, inhabit soil and spread sporadically by swimming through water until they enter your orange tree's roots, where fungi germinate, according to the University of California IPM Online.
Certain factors greatly increase the incidence of root rot disease in your orange tree. Phytophthora-Diaprepes complex causes injury and eventual root rot in orange trees. Diaprepes root weevils (Diaprepes abbreviatus) feed on the roots of an orange tree. This injury weakens the tree, resulting in a prime environment for the invasion and germination of soil-borne phytophthora fungal pathogens, according to the University of Florida IFAS Extension.
Waterlogged soil is also a key factor in the incidence of fungal root rot as citrus trees are very sensitive to poorly drained sites. When soil does not drain, trees absorb too much water. The tree's inability to absorb the correct amounts of water and nutrients causes a decline in health. Additionally, the standing water promotes the collection of fungal spores.
When phytophthora root rot invades your tree, the slow decay of roots results in a steady decline of your orange tree's health. Look for above-ground symptoms of discolored leaves that become pale or yellow and premature defoliation. A potential sign of waterlogged roots is splitting fruit or fruit drop. Leaves may display a notched appearance if weevils are present. Adults feed on foliage and larvae feed on tree roots. Roots become girdled or soft. Your orange tree will weaken and eventually die.
Maintain vigorous trees and well-drained soil to prevent orange tree root rot. Avoid overhead irrigation that promotes fungal germination. For chemical control of phytophthora fungi, apply a fungicide with the active ingredient mefenoxam to the soil of bearing or non-bearing orange trees, according to the University of California IPM Online. Fungicidal application will help decrease the population of fungal pathogens but cannot cure rotten roots or infections. Insecticides with the active ingredient fosetyl-Al offer protection and diagnostic control of weevils. Contact a licensed professional or your local county extension agent to determine an appropriate control program. Do not apply more than one chemical to your orange tree in an attempt to treat different contributing factors.