Page 178 - FRUTAS DEL TRÓPICO

178 Frutas del trópico

Root to root infection and moving water disseminate the pathogen. However, spread
usually involves insects or man (Jones, 2000). Regular inspection and eradication programs

are essential wherever Moko disease is established. These include: (1) early recognition of the

disease; (2) removal of the male bud; (3) rigorous disinfestation of farm implements, especially

machetes that are used for bud removal and mat maintenance; and (4) destruction of affected

and neighboring plants with herbicides. These sites can be replanted 6-12 months after all host

residues have decayed.

Black sigatoka (black leaf streak). Black sigatoka is caused by the ascomycete, Mycosphae-

rella fijiensis (anamorph: Pseudocercospora fijiensis); it is the most important disease of bana-

na. Another disease, yellow sigatoka, produces similar symptoms and has a wider geographic
distribution, but black sigatoka is more aggressive and has a wider host range (Stover and

Simmonds, 1987). On the cavendish cultivars that are used by the export trades, fungicidal

control for black sigatoka is three to six times more expensive than that for yellow sigatoka.

Black sigatoka affects plantain and banana cultivars that resist yellow sigatoka, and causes greater

defoliation and yield losses. In most of the lowland humid tropics black sigatoka has displaced

yellow Sigatoka as the predominant leaf spot on banana.

Symptoms begin as reddish brown flecks on the lower leaf surface. They enlarge to
become visible on the upper surface, and elongate, darken and often develop a wet appea-

rance. Dark borders and yellow haloes surround the spots as they exceed 1-2 cm in length,

and as the spots mature their centers become grey and sunken. In susceptible cultivars, spots

coalesce until the entire leaf surface is killed. The disease causes fruit to ripen prematurely (a

serious problem when fruit are shipped), and in severe cases the bunch does not develop fully.

Although symptoms of black sigatoka can be difficult to distinguish from those of yellow siga-

toka, the respective anamorphs are distinct: conidia and conidiophores of the former, P. fijiensis,

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