Agriculture Reference
In-Depth Information
Importance
Periodic epidemics of yellow crinkle occur, usually after
periods of hot, dry weather. Young plants that have not
f flowered are rarely affected, with most losses occurring
during the first fruiting period.
Management
•
Maintain a larger number of trees during the fi rst year
so that diseased trees can be removed without greatly
reducing the stand.
Unlike dieback, ratooning plants does not promote
healthy shoots.
•
FUNGI
Fig 14.13 Anthracnose ripe fruit rot on papaya.
ANTHRACNOSE
■
Cause
The fungus
Colletotrichum gloeosporioides
.
Symptoms
During ripening, sunken, brown spots develop on the
surface of fruit. Usually these spots develop on the side of the
fruit that faces outwards from the trunk before harvest.
During storage, the spots continue to enlarge, often
coalescing to form large, rotted areas that extend well into
the f flesh. Under conditions of high humidity, characteristic
salmon-pink spore masses are produced on the surface of
lesions.
Fig 14.14 Spores of anthracnose.
Source of infection and spread
Infection by
Colletotrichum
occurs before harvest. Spores of
the fungi are produced on dead and dying leaves and
leafstalks, and are spread to fruit by wind and rain during
wet weather. Infections established as a result of such
contact remain dormant in the peel of fruit until ripening,
after which they develop rapidly. Spread of the disease after
harvest from fruit to fruit is not significant. The
environment plays an important part in the incidence of
anthracnose. Fruit that have been exposed to the sun or
cold winds often ripen prematurely and are particularly
prone to spotting. Lower temperatures favour disease
development by prolonging ripening and giving the fungus
more time to develop.
Management
•
Establish plantations in warm, sheltered areas.
Avoid very susceptible lines when selecting seed.
•
Apply recommended fungicides to fruit in the
plantations.
•
Apply postharvest fungicide treatments.
•
BLACK ROT
■
Cause
The fungus
Phoma caricae-papayae
.
Importance
Anthracnose is a common disease that can cause
substantial losses of harvested fruit.
Symptoms
Black rot is a black, shrunken rot of young fruit,
generally extending from the stem end or a point of
