A multi-disciplinary research team from University of the Philippines Los Baños has discovered that extract from cashew shells can be used to kill termites.

A report on the UPLB-RDE website said a team from the Institute of Chemistry-CAS and Department of Forest Products and Paper Science-CFNR said cashew nut extract could be used as a non-synthetic solution to control the spread of Philippine milk termites (scientific name: Coptotermes vastator)

Composed of Mr. Edison G. Boongaling, Dr. Hidelisa P. Hernandez, Dr. Ernesto J. del Rosario (IC-CAS) and Dr. Menandro N. Acda (DFPPS-CFNR), the team described cashew nut shell liquid as a viscous, reddish brown extract that can be derived from cashew shells via hot oil extraction, roasting at high temperatures and mechanical extraction.

For its experiment, the group air-dried cashew nut shells for two weeks and the crude CNSL was expelled using a press. After filtration, chemical evaluation and thin layer chromatography was done.  From the crude CNSL, the group isolated and prepared the following components: anacardic acid, cardanol, and methyl anacardate.

They then collected C. vastator termites from various colonies found inside the UPLB campus and placed them in an artificial environment inside the laboratory. Within an hour of collection, the termites were subjected to two bioassays: contact toxicity and 'no choice feeding'.

In contact toxicity, loamy soil was treated with CNSL solutions of 0.1, 1, 10 and 100 percent concentrations. The termites were placed inside petri dishes in controlled conditions for two weeks.  The 'no choice' feeding bioassay was performed on the other hand to see if the CNSL and its anacardic acid, cardanol, and methyl anacardate components can kill termites when ingested. Solutions also of 0.1, 1, 10 and 100 percent concentrations were applied to filter paper served as food for the termites for two weeks.

Results showed that the natural CNSL was toxic to termites. It controls termites from tunneling into the soil, and at only 10 percent concentration, the CNSL was able to kill all C. vastator termites within a day.

On the other hand, it was observed that the CNSL was not potent by ingestion but had an anti-feeding effect on the termites. Meanwhile, using the individual anacardic acid, cardanol, and methyl anacardate components of the CNSL killed termites at a high rate even at only 0.1 percent concentration.

The researchers said their study could pave the way for commercial exploitation of the kasoy derivative as termiticide. Since CNSL is environment-friendly, it would be a viable alternative to chemical insecticides which persist in the soil after application.

The group said CNSL and its derivatives may be developed into a solution for delivery into the soil to directly kill termites, or a paint-on material, which may prevent termites from infesting cut lumber. Because it can be ingested, it may also be used in developing a cheap bait to sustainably control termites over a long period of time.

They said companies could also use CSNL to develop resins, automotive brake linings, heatproof and waterproof paint, corrosion-resistant varnish and insulating enamels.