Mycosphaerella leaf spot diseases of bananas - CBS

Session 1
D.R. Jones
The first record of black leaf streak disease in Africa was from Zambia in 1973
(Raemaekers, 1975). The publication of this outbreak is convincing but the identity
of the pathogen could not be confirmed from specimens sent to the UK, therefore
doubt remains as to the authenticity of the report (Dabek and Waller, 1990). The
next record was from Gabon in 1978. Frossard (1980) believed it might have been
introduced on planting material from Asia. The disease then spread steadily through
Central and West Africa reaching Côte d’Ivoire, Nigeria and Ghana in 1985-1986,
and Uganda and Malawi in 1990 (Table 2). A second, separate introduction of
M. fijiensis into Africa is thought to have occurred in 1987 on the island of Pemba.
This outbreak is believed to have led to the pathogen spreading to the island of
Zanzibar and coastal areas of Tanzania and Kenya (Carlier et al., 2000a). In 2000,
M. fijiensis was recorded in Madagascar for the first time.
The Australian experience
Stover (1978) believed that M. fijiensis may have originated in the Papua New
Guinea-Solomon Islands area and disseminated around the South Pacific with
banana leaves or planting material. This possibility is suggested by the discovery
that isolates of M. fijiensis are more diverse in the Papua New Guinea /Philippines
region than elsewhere, an indication that the area may be the centre of origin of
the pathogen (Carlier et al., 2000a). Therefore, it is likely that M. fijiensis may have
been present on banana on islands in the Torres Strait and on the tip of Cape York
Peninsula, Australia long before its discovery on the first plant pathological survey
of the area in 1981 (Jones and Alcorn, 1982). The pathogen may not have spread
further south in Australia because of the barrier presented by the Cape York
Peninsula, which is a large, remote area of native bush with comparatively few
communities and banana plants. After 1981, better land and air communications,
which encouraged more tourists and people seeking an alternative lifestyle, led to
a higher risk of spread. During the 1990s, M. fijiensis was regularly eradicated from
isolated outbreaks on small plantings within the Peninsula. In all cases, the origin
of the inoculum could not be positively determined. In 2000, an outbreak occurred
on a commercial banana planting at Daintree on the northern fringe of the more
heavily populated coastal strip centred on Cairns. The grower was compensated for
the destruction of his crop by the Australian banana industry. Although eradicated,
the close proximity of this outbreak to the main banana growing area was worrying.
Towards the end of the wet season in April 2001, M. fijiensis was detected on
unmanaged (feral) banana plants and also on cultivated plants in an adjacent farm
in the Tully Valley, which is in the heart of the commercial banana-growing area
in North Queensland centred south of Cairns. Subsequently, the pathogen was
reported from other locations in the same area. An eradication campaign was
immediately mounted. This campaign gathered momentum when the governments
of banana-growing states and the Commonwealth Government pledged funds.
Measures included: (1) establishment of a special banana quarantine area, (2) a ban
on the movement of fruit from this area to other banana-growing areas in Australia,
(3) close monitoring of crops and the diagnosis of any leaf spots detected,
(4) destruction of fields where affected plants were found, (5) drastic pruning of all
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