Agriculture Reference
In-Depth Information
the fl ower perianth and slowly developing along with fruit growth. The end of
the fruit darkens and later is covered with spores looking like a lit cigar. The
disease is found in Latin America, West Africa, Egypt and Australia. The pulp
develops as a dry rot. Removal of pistil and perianth 8-12 days after bunch
emergence and polyethylene bunch covers help to reduce incidence.
A complex of dif erent organisms is known to cause the most serious
worldwide postharvest disease - crown rot. The wound caused when the
bunch is dehanded is colonized by the organisms, the rot spreading into the
pedicels during shipping and sometimes into the pulp. A number of organisms
have been found, with the actual complex varying with region; most common
isolates have been
Colletotrichum musae
,
Fusarium
spp.,
V. theobromae
,
B.
theobromae
and
Ceratocystis paradoxa
.
Spores are carried by wind or rain splash;
however, dehanding knives and delatexing tanks may be bigger sources. Good
dehanding practices, with clean cuts using sharp knives, and sanitation of
packing sheds and areas are essential. Exporters use alum and a fungicide to
try to control this infection.
Anthracnose on the fruit skin and neck rot are both caused by
C.
musae
and can be a serious problem when the fruit becomes overripe. Sanitation and
postharvest fungicide are used for control.
Insect pests and nematodes
Insect pests are generally of minor importance (Table 8.6). Occasionally,
severe fruit scarring can occur. Borers are a problem where control practices,
such as planting clean material and insecticide schedules, are not followed.
The continuous nature of banana production makes pests such as nematodes
more important (Table 8.6).
The main insect problem in many areas of the world is the black weevil
(
Cosmopolites sordidus
). The weevil lays eggs in the corm, and the larvae
coming from them bore into the corm, causing extensive corm rotting because
of secondary infection. The damage to the roots and the expansion of the
rotting to most of the corm leads to weakening of the plant, which lowers
production, and frequently toppling of the plant with total loss of the bunch.
The main control measures should be paring and disinfecting the corms
before planting, eliminating residues of old plants before a new planting,
fallows and the use of traps with pheromone or pseudostem piece traps; both
attract the adults. In the pheromone traps, the weevils are drowned and in the
pseudostem piece traps they can just be hand-collected or can be poisoned if
an insecticide is added to the piece.
Nematodes can severely limit production, with the extent of the problem
varying with cultivar, soil conditions, type of nematode and plant vigour.
Nematicides are used for fruit destined for export and are applied every 4-6
months, but they are expensive, their use has to be continued and many of
them are being banned by the importing countries. More economic measures
include: improved fallow to eliminate old material, done in combination with
