Agriculture Reference
In-Depth Information
CORDANA LEAF SPOTS
■
Cause
The fungus
Cordana musae
is present in all banana
growing states while
C. johnstonii
is known to occur on the
Atherton Tablelands in north Queensland, parts of
southern Queensland and northern New South Wales.
Symptoms
Mature leaf spots of
C. musae
are elliptical or oval shaped
and up to 100 mm in length. Spots are brown with zonate
patterns on the upper surface and grey underneath,
bordered by a conspicuous bright yellow halo. Mature
lesions of
C. johnstonii
are smaller (
25 mm) than that
of
C. musae.
Lesions tend to have a cat's-eye appearance.
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Fig 5.22 Symptoms of
Cordana musae.
Inset: symptoms of
C. johnstonii.
Source of infection and spread
Large numbers of spores produced on the underside
of infected leaves spread during wet, windy weather.
The fungus
C. musae
often invades leaf tissues weakened
by other pathogens whereas
C. johnstonii
appears to be
a pathogen in its own right.
Importance
This is usually a minor disease controlled by the leaf spot
and speckle spray program.
Fig 5.20 Cigar end symptoms have a characteristic ash-grey coating
resembling a burnt cigar tip.
Management
•
Apply the recommended fungicides.
CROWN ROT
■
Cause
Fungi commonly isolated from banana fruit with crown
rot are
Fusarium pallidoroseum, Verticillium
sp. and
Colletotrichum musae
.
Symptoms
Blackening and rotting of the cut ends of the hands occur.
As the fruit ripens, the rot advances rapidly down the fruit
stalks, causing them to fall from the hand.
Source of infection and spread
Crown rot fungi are present on dead f flowers and plant debris
that accumulate in packing sheds. They gain entry to fruit
through fresh wounds made to cut the hand from the
peduncle and later split into clusters. Infection often occurs
when washing fruit in tanks, as spores can be present in the
water. The disease develops while bananas are held in storage.
Fig 5.21 Cordana leaf spot in banana. Spots are surrounded by a
conspicuous bright yellow halo.
