important are as follows:
- Banana Weevil (Stem Borer or Beetle)—the most serious, all over the world,
especially in neglected plantations. Adult weevils live for up to two years in the
stems, the larvae burrow into the corms, leaving tunnels visible if the plant is cut
open; the plants are weak, yields are low. Control: plant clean suckers and treat them
with insecticides, cut off old stems at ground level and cover with soil, chop up the
old stems and spread them on the soil as a mulch, and encourage healthy plant
growth with fertiliser, mulching, weeding, etc. Traps can be made with old stems
split and placed around the clumps the insects can be collected from them by hand. - T h r i p s—fruit skins become discoloured or cracked. Very difficult to control.
- Nematodes—a worsening problem in some areas where the tolerant Gros Michel
clones are replaced with the susceptible Cavendish clones. The roots are destroyed,
leading to wilting and sometimes plants falling over.
Control: plant only clean material, and crop rotations, such as with sweet potatoes.
DBCP is sometimes used, 2–4 times a year, but this chemical is very dangerous and
has caused widespread sterilisation in plantation workers from Central America and
the Caribbean to the Philippines and West Africa. - Other pests—Fruit Scarring Beetle (North America), Scab Moth (Pacific) and
aphids, which carry and spread virus diseases.
Diseases: four of the most common diseases are described below:
- Panama Disease—one of the most catastrophic diseases in the world, it is found
in most countries where bananas are grown, especially in acid soils. The fungal
spores can survive in the soil for 20 years or more. Symptoms: the outer, lower
leaves become yellow, then hang down and collapse; the inside of stems and
rhizomes become purple.
Control: ideally with resistant varieties, also plant clean material into clean soil, or
flood fallow to 1–2 metre depth for six months, or increase soil pH by liming, or
improve drainage. - Leaf Spot (Black Sigatoga)—a serious problem in the tropics, causing yield loss
and premature fruit ripening. Symptoms: faint yellow spots, first on the leaves, the
spots become necrotic at the centre and join together in lines parallel to the lateral
veins; leaf margins die. Control: plant only resistant varieties, or spray Bordeaux
mixture or mineral oil sprays every 2–4 weeks at 11 litre/ha. - Cigar End Rot—fruit tips look like the ash on the end of cigars. Worse with cool
nights. Control: remove the end of the inflorescence, beyond the developing fruits. - Bunchy Top Virus—occurs in the Pacific, Far East, Australia, Egypt and the
Congo. Symptoms: green streaks on the secondary veins on the underside of leaves
and on midribs and petioles (leaf stalks); lower leaves become brittle and stunted;
petioles are short, creating a “bunchy” effect. The fruits are spoiled, often unsale-
able. Controlled by planting clean material and controlling aphids.
virus diseases and a range of fruit rots and spots.
Other diseases include Black Leaf Streak, Bacterial Wilt (Moko disease), other
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GROWING FOOD – THE FOOD PRODUCTION HANDBOOK 251
Pests: more than 200 insects like to eat bananas and banana plants. The most