New invasive species behind coconut devastation

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)