Tiny insect is farmer crops’ protector in Cordilleras

A tiny wasp-like insect has evolved as the "knight in shining armor" protecting vegetable crops in the Cordilleras.

Tinier than a mosquito, the friendly insect is called Diadegma semiclausum, fondly called the "good guy" in the research world.

The "bad guy" is the diamondback moth(DBM), so-named because of the diamond shapes on its back. DBM voraciously feeds on the foliage of crucifers (cabbage, Chinese cabbage, cauliflower, broccoli, pechay, mustard, and radish).

Until Diadegma was introduced in 1993, DBM ravaged crucifer farms, rendering farmers helpless because the pest had become resistant to pesticides being used by vegetable farmers.

There was even a time when farmers concocted the so-called "cyanide cocktail", a combination of sodium cyanide and other potent chemicals, to control the DBM. The practice almost brought about the collapse of the Cordillera vegetable industry as consumers stopped buying their produce.

Then came a research project on the Diadegma sponsored by the Taiwan-based Asian Vegetable Research and Development Center (AVRDC), the Manila-based Asian Development Bank (ADB), and the Los Baños-based Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD).

Under the project, Diadegma are reared in great number by the Benguet State University (BSU) in La Trinidad town and the Department of Agriculture-Bureau of Plant Industry-Benguet National Crop Research and Development Center (DA-BPI-BNCRDC).

A limited number also are now being reared in Atok (Benguet), said Dr. Eulogio Cardona Jr., project in-charge of the BSU-Asian Vegetable Network Diadegma Rearing House at BSU.

The friendly insects multiplied are given free to farmers, who in turn release the "good guys" on their farms.

Dr. Cardona told this writer and Agriculture editor/columnist Zac Sarian that the Diadegma control the DBM larva by parasitization.

First, the adult lays eggs on the host DBM larva. Normally, only one egg is laid. Only DBM are parasitized by Diadegma.

After 2-2.5 days, the egg emerges to parasitize the larva and feeds on the DBM host’s body fluids. The host’s internal organs are damaged until the host insect is totally consumed.

Diadegma can lay 200-300 eggs in its lifetime of almost two months.

Before the 1990s, losses inflicted by the DBM were heavy, said Dr. Cardona, who had trained at AVRDC on the technology. Now, with the thousands of "good guy" Diadegma guarding farmers’ fields, damage caused by "bad guy" diamondback moth is minimal. – Rudy A. Fernandez