Agriculture Reference
In-Depth Information
split. Death of the parent pseudostem generally follows,
but suckers do not necessarily die.
The most characteristic symptom is seen by cutting through
the pseudostem of an affected plant near ground level
where a dark brown to black discolouration of the water-
conducting tissues is evident. Corms, when cut, show brown
or black lines running through the tissues. Infected plants
rarely produce a marketable bunch. Occasionally, a bunch
matures and the fungus may be present in the bunch stalk.
Brown vascular strands are visible in the centre of the stalk.
Source of infection and spread
The disease is usually introduced in planting material.
Once established, the fungus persists in the soil for many
years. It enters the plant through the roots and grows into
the water-conducting tissues of the corm and pseudostem.
Spread from a diseased parent plant into the suckers also
occurs.
Several independent, radially spreading patches usually
occur in a plantation. These eventually join, making
continued fruit production uneconomic.
Importance
Four races of
Fusarium oxysporum
f.sp.
cubense
have been
described; three of which affect banana (race 3 is a
Fig 5.36 Banana tree showing a severe infection of Fusarium wilt.
Note that the older leaves are dying.
pathogen of
Heliconia
spp.). Race 1 is widespread in
eastern Australia where it causes major damage in Lady
finger plantations. Race 2 affects cooking bananas and
has been recorded in northern NSW. Race 4 affects
Cavendish in subtropical regions where cold winter
temperatures are a predisposing factor. Tropical race 4
(TR4) is currently found only in the Northern Territory
where it is responsible for destructive epidemics in
Cavendish plantations.
Management
•
Use planting material from disease-free plantations
or preferably from tissue culture.
Do not plant susceptible cultivars on land where the
disease has occurred.
•
Avoid a site where surface run-off from a diseased
plantation can infest the soil populations.
•
Avoid poorly drained soils.
•
Observe quarantine measures designed to prevent the
spread of subtropical and tropical race 4 of Fusarium wilt.
•
Fig 5.35 Fusarium wilt in a banana plantation showing yellowing
in the infected trees.
