DNA
analysis has identified an invasive and
alien species behind the devastation of coconut trees.
Coconuts die because scale
insects block the pores, preventing leaves from producing nutrients for the
tree.
DNA analysis uses genetic
markers—gene or DNA sequences on the chromosome—to identify individuals or
species. Because genes
encode observable characteristics, DNA analysis or gene mapping is a popular
scientific tool, used for example in plant and livestock breeding and in biotechnology.
In 2014, DNA markers showed
that the scale insects were a mixed population of Aspidiotus destructor and Aspidiotus
rigidus, the latter a new species in the country.
According to Celia Medina and
Barbara Caoili of the University of the Philippines-Los Baños (UPLB), Aspidiotus rigidus originated in
Mindanao and was first reported in Sangi island in Indonesia. It is not known
whether the invasive species entered the country by air or carried by humans,
animals or through imported ornamental plants. As an introduced species, it has
no known natural enemies here.
Ms. Medina, a Professor of
Entomology and the Director of UPLB's National Crop Protection Center, and Ms. Caoili,
an insect scientist working at the molecular level, identified the Aspidiotus
rigidus species.
In 2011, scientists first
identified the scale insect devastating coconut farms to be Aspidiotus destructor,
a species that is found in the country and has natural predators. In 2014, the
DNA analysis identified Aspidiotus rigidus, the new invasive species which has
no known natural predators.
The difference is important.
The Philippine Coconut Administration (PCA) and the Bureau of Plant Industry
started in 2013 the field release of natural predators to control Aspidiotus
destructor. A different
tack will be made after Aspidiotus rigidus was detected early this year—combining chemical pesticides with natural predators.
After the earliest report of
an outbreak in 2010, the PCA conducted research on the nature and the possible
control of the outbreak. Interim interventions until January 2014 included the
spraying of cochin, a coconut-based oil, mixed with dishwashing detergent.
Because cochin oil is not a poison, it is safe even for the applicator; it does
not kill but instead loosens the wax that covers the insect and suffocates it.
To prepare for the future,
UPLB scientists will look at the biology and the relationships of crops and
their pests and diseases and how they all react to changes in climatic
conditions. De La Salle University will identify and assess the risks and the
rapid response needed to other invasive pest species affecting important crops.
The race is urgent to prevent
the infestation from spreading. Some 25 million Filipinos are directly or
indirectly dependent on the coconut industry which supplies more than half (59
percent) of world exports. Among the Top five net foreign exchange earners, the
industry averages US$1 billion a year.
Over 324 million nut-bearing
and non-bearing trees are planted in 3.5 million hectares in 68 of 79
provinces; that's over a fourth (27 percent) of total agricultural land in the
country. (SciPhil)
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