Agriculture Reference
In-Depth Information
FUNGI
BLACK ROOT SYNDROME
Cause
A complex of pathogens including Cylindrocarpon
destructans , Rhizoctonia spp, Pythium spp. and Fusarium
spp., together with nematodes and environmental stress,
has been implicated.
BLACK PLUG
Cause
The fungus Phoma sp.
Symptoms
The characteristic symptom is the development of a large,
dark brown to black spot on the fruit. As the fruit ripens
and the spot expands, a white fungal mycelium develops
and is concentrated around the margin of the affected area.
The diseased area is easily removed as a 'plug'. The depth
and width of the plug are similar.
Symptoms
Leaves collapse on one side of the plant. The crown area
between the vascular tissue and the outside edge becomes
necrotic. Roots become necrotic.
Source of infection and spread
The disease is complex and difficult to describe.
The fungi listed are all soil-borne. Poor soil aeration
and microbial activity are thought to be contributing
factors.
Source of infection and spread
The fungus survives on colonised plant tissue and plant
debris. Spores are spread by wind and rain with wet
weather favouring the disease.
Importance
This disease has only been a problem in recent
years on a few farms. There is concern that it
could become more important if there is no
adequate replacement for methyl bromide
as a soil fumigant.
Importance
Black plug is a minor cause of fruit rot in Australia.
Management
Apply cultural and chemical management practices used
for other fruit rot diseases (these will provide reasonable
control of black plug).
Management
Use soil fumigation to reduce damage to tolerable
levels.
Use management practices to increase soil aeration.
Fig 18.5 Advanced black plugs on strawberry. Note the black centre
with white fungal growth around the perimeter.
Fig 18.6 Black root rot showing typical field symptoms. Inset: 'rat tail'
effect in damage to feeder roots.
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