Agriculture Reference
In-Depth Information
Losses are most likely to occur when orchards and
vineyards are planted on land recently cleared of native
vegetation susceptible to the fungus. Armillaria root rot
may cause serious losses in apple, banana, citrus, custard
apple, grape, macadamia, pear and stone fruit orchards.
Symptoms
Because Armillaria damages the root system, the
symptoms above-ground are similar to those caused by
other root-infecting pathogens. Plants slowly decline,
showing leaf yellowing, reduced leaf growth and twig
dieback. Armillaria first causes death of limbs and finally
death of the plant. Gumming often occurs on the trunk
and crown roots.
Fig 2.7 Armillaria in bark. Sheets of white fungal growth have
developed beneath the bark.
Diagnostic symptoms are the presence of cream-coloured
fungal growth, sometimes fan shaped, just beneath the
bark of the crown and large roots, and a strong mushroom
smell. Black, cord-like threads of the fungus, commonly
Fig 2.5 Advanced symptoms of Armillaria root rot in peach.
Fig 2.6 Root symptoms of Armillaria showing black strands or
rhizomorphs, which grow around the external root surface and may
help the disease spread.
Fig 2.8 Honey-coloured mushrooms of Armillaria. These develop as
clusters at the base of affected trees. Inset: underside, showing gills.
