The coconut odyssey - the bounteous possibilities of the ... - ACIAR

ought from regions where it is
absent. �e beetle can also be very
destructive if it invades a new region.
For example, a coconut variety
brought, because of its large fruit,
from Malaya to Solomon Islands in
the 1920s suffered very severe damage
from the local Brontispa beetle.
Conversely, when the beetle entered
Australia’s Cape York Peninsula
recently as a new arrival, it wreaked
extensive damage on coconuts and
some ornamental palms.
Coconut palms also exist that are
resistant or tolerant to bud rot and
lethal yellowing disease—both
serious scourges of coconuts in many
parts of the world (see Chapter 4
for a more detailed description of
diseases and pests of the palm).
One of the most interesting
examples of invisible tolerance to a
disease was discovered in Vanuatu
during the 1960s, when many
varieties of coconut were imported
for research. Many of these exotic
coconut palms died, and local people
accused the researchers of importing
a dangerous disease along with the
palms. It turned out, however, that
there was a viral pathogen present
in the local palms, which were so
tolerant of it that they showed no
symptoms. Exotic varieties, on the
other hand, had no tolerance and
began to succumb to the virus, later
found to be confined to Vanuatu.
�e discovery was a blow to the
research project because there had
been hopes of breeding new hybrids
for export to neighbouring countries,
but export was now too risky.
Molecular tools show promise of
becoming useful in the long term
in identifying, at moderate cost,
populations with tolerance to a
particular species or strain of attacker,
or to an environmental stress. �is
approach might render unnecessary
large field trials designed to compare
the tolerance of populations. Such
trials are costly and subject to
uncertainty about the intensity of
exposure to the hostile organism.
�e strand posed few
biohazards
�roughout its long evolution in its
natural environment on the strand,
the coconut has not been exposed
to particularly strong selection
pressure from pests and diseases.
�is is because many small-island
environments do not carry complex
populations of plants whose
associated insects and pathogenic
microorganisms would prey upon or
invade neighbouring coconut palms.
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�e palm planted elsewhere faces
more threats. Its foliage is palatable
not only to many insects but to all
herbivorous animals. Where the
palm coexists with horses, cattle,
buffalo, sheep, goats or the like, the
foliage must be protected for several
years until it is out of their reach.
Many nonselective pests—such
as stick insects, locusts, the palmdart
caterpillar, scale insects and
whitefly—inflict foliar damage on
coconut palms episodically, especially
in a monoculture (plantation)
situation (see Chapter 5). �e soft
tissue of the central bud, particularly
in the palm seedling, also attracts
creatures ranging from beetles, birds
and pigs to elephants!
Diversity among Dwarfs
�ree main subgroups can
conveniently be identified among
the Dwarfs: the ‘stumpy’ or compact
Dwarf of the South Pacific (named
Niu Leka or Niu Leha in Polynesian
languages); the ‘village’ Dwarf, found
scattered in villages throughout
the Pacific; and the Malayan or
Nias Dwarf. �e last two types
are fairly uniform, especially the
highly inbreeding (self-pollinating)
village Dwarf, whereas the stumpy
Niu Leka is mostly an outbreeder.