A ubiquitous part of breakfast, the grapefruit (Citrus x paradisi) possesses a bitter to bittersweet flavor. The sweetest fruit is produced in climates with hot days and warm or hot nights. Grapefruits are evergreen and have short supple thorns. More than 30 viruses or virus-like diseases affect citrus trees, however, including grapefruit trees.
Citrus Tristeza Virus
Citrus Tristeza virus is one of the most damaging diseases that affects grapefruit trees. Symptoms include yellow foliage, cupped leaves, loss of tissue between leaf veins, pitted stems and smaller fruits. If the rootstock becomes infected, the tree will decline and eventually die.
Also known as scaly bark, Psorosis is a virus or virus-like disease that occurs mainly in grapefruit trees. Patches of scaly or peeling bark appear on the branches and twigs of affected trees. As the patches get bigger, the tree suffers stress and becomes less productive.
The fungus Hendersonula toruloidea causes sooty canker or limb wilt on grapefruit trees. The fungus enters the tree through an injured area and grows under the bark. The sooty black spores under the bark grow into the sapwood of the tree, causing the foliage to wilt, turn brown and die. Infected branches will die back to the cankered areas.
Rio Grande Gummosis
Rio Grande gummosis is another fungus that attacks injured grapefruit trees. Narrow cracks appear in the bark of affected limbs or trunks. Yellow water-soluble gum oozes from the cracks and forms gum pockets under the bark. The exposed sapwood decays and dies. Rio Grande gummosis can also infect the heartwood of a tree.