Sigatoka, Science, and Control - Banana Cultures - page 90

were capable of transporting spores of the fungus associated with Siga-
toka disease great distances. A second and more likely means by which
Sigatoka traversed the globe was via the movement of Musa propagat-
ing material and banana leaves (often used as packing material). Banana
breeding programs initiated in the 1920s by the British government and
the United Fruit Company received plants from Asia and the Pacific. One
canalsoassumethatotherMusaspecimensreachedtheAmericasvianon-
institutional efforts. In addition to banana boats, the growing amount of
merchant marine tra c through the Panama Canal probably increased
the number of intentional and unintentional plant introductions. 16
The pathogen associated with Sigatoka, Mycosphaerella musicola
Leach, was an airborne fungus that infected the young leaves of banana
plants. 17 Infected leaf tissue developed yellow streaks that subsequently
turnedintoblackishspots.Severelyinfectedleaveseventuallyceasedfunc-
tioning and drooped. The loss of leaf area affected the development of
the fruit: diseased plants produced low-weight bunches. 18 Moderately in-
fected plants tended to produce fruit bunches that at first glance were
indistinguishable from bunches on healthy plants. However, upon being
harvested, the bananas quickly turned soft and yellow, rendering them
unfit forexport. Such fruit was known as ''ship ripes,'' ''leaf spot ripes,'' or
''Cercospora fruit.''
Plant pathologists considered M.musicola Leachtobeamildpatho-
gen, greatly affected by environmental conditions, including temperature
and humidity levels. In Honduras, some observers initially hoped that a
seasonalchangeintemperatureand/oratmosphericpressurewouldcheck
the pathogen's spread. 19 Unconvinced that weather changes alone would
bring Sigatoka under control on the company's sprawling monocultures,
Vining Dunlap began testing fungicides within weeks of the epidemic's
outbreak. As early as 1914, researchers in Fiji had recommended apply-
ing Bordeaux mixtures (copper sulfate and lime) to control M. musicola
on banana plantations. 20 During the 1920s, Norman Simmonds tested a
variety of control techniques, including copper-lime dust, on diseased
banana farms in Australia. 21 The general abilityof copper-lime and sulfur-
lime compounds to control the fungus was therefore known in 1935,
but their e cacy under the environmental conditions found on Central
American banana plantations remained uncertain. By the end of 1936,
Dunlap reported that Bordeaux mixture (copper sulfate, lime, and water)
applied on seven- or fourteen-day cycles provided adequate control, par-
ticularlyduringtherainymonthswhenmanyotherfungicidalcompounds
failed. 22