Oak root fungus (Armillaria root
rot)—Armillaria mellea
Symptoms on trees infected with oak root fungus vary. If the disease develops quickly, leaves tend to
be small and chlorotic and drop early. Shoot growth is poor and shoot dieback is common. Trees with slow
development of the disease show premature fall coloring of the foliage. Foliage symptoms may be apparent
on only one or two scaffolds if the crown is only partially girdled. Dark rhizomorphs (shoestringlike
structures) develop and grow into the healthy, underground tissue.
Identification
Solutions
If less than half of the crown's circumference is girdled, it may be possible to save the tree. In late
spring, remove the soil from around the crown area and cut away all bark and tissue of the crown invaded
by the white leathery fungus. Leave uninfected tissue intact and keep the crown exposed for drying. If
more than half of the crown is infected, the tree should be removed. For replanting, choose resistant
rootstocks. Avoid planting in infected soil. Maintaining trees with good fertilization and irrigation
programs helps preserve their natural resistance to this fungus. | 
Aboveground
symptoms of oak root fungus
Rhizomorph
(top) with healthy root
|
