Root rot can destroy fruit trees, but gardeners can take several steps to prevent a root rot infection. Choose resistant fruit cultivars, then plant in a location with well-draining soil. Keep trees pruned annually to promote good air circulation and reduce the chance of fungal infection. Fruit trees that get root rot are often too infected to save since initial symptoms occur underground. By the time gardeners notice above-ground symptoms, it may be too late to reverse.
Fruit trees can experience two types of root rot: Armillaria root rot and Phytophthora root rot. Both are caused by fungus.
Armillaria Root Rot Symptoms
Fruit trees with Armillaria root rot develop yellow or brown leaves that can fall off the tree early. Fruit trees can bear a bumper crop of fruit before dying. Trees experience reduced or no growth, with stems, branches and twigs dying back at the tip. Trees with a severe Armillaria root rot infection weep resin, gum or watery liquid.
Tiny white or cream colored fungi are the most distinctive features of Armillaria root rot. These fungi appear near the base of the tree trunk and emit a strong mushroomy smell, according to the University of Illinois.
Phytophthora Root Rot Symptoms
Phytophthora root rot displays many of the same symptoms as Armillaria root rot. Affected fruit trees grow less or not at all, and the tips of branches and twigs can die back. Tree leaves turn yellow or may display a greenish-purple tinge. The trees typically take several years to die though some may die within a season.
The predominant cause of the fungi that cause both types of root rot is wet weather. Trees planted in poorly draining soil will be more vulnerable to developing root rot since their roots can be standing in water much of the time. Moist, boggy spring weather can also lead to infection.
Certain trees are more resistant to root rot. Pear trees, plum trees and certain apple trees resist Phytophthora root rot. Mazzard or Morello cherries are more resistant than other types of cherry; Mahaleb is a more susceptible cherry cultivar. Pear, persimmon and Mazzard cherry are relatively resistant to Armillaria root rot. Peach and apple are more susceptible to Armillaria root rot.
Affected trees can be dug up and replanted elsewhere; this sometimes works to keep the tree healthy for a time. Soil around the base of the tree can also be dug up to expose and dry out the root collar from spring to autumn. Fungicides will not control root rot, and most infected trees eventually die after several years.