The Department of Agriculture has recommended the use of biological control agents against rice black bug (RBB) and armyworm that recently infested some areas in Mindanao.

According to the DA’s Bureau of Plant Industry (BPI), a fungus called Metharizium can be used to control RBB while the Nuclear Polyhedrosis Virus (NPV) can be used against armyworm.

The Metharizium fungus is  entomopathogenic  that cause disease to the   insects, seriously disabling or killing them. The NPV, on the other hand, is a virus that destroys the cellular structure of armyworm until it can no longer maintain life.

‘Timed’ attacks

Farmers have noticed that the RBB and armyworms—present in the whole country except in the Cordilleras—attack in swarms during specific times of the year.

The BPI explained that the RBB are actually present in the farms year-round but they are very much attracted to light such that three to five days before and after a full moon, they become very active and congregate.

According to the BPI, the recent RBB incident during the Palarong Pambansa happened during a full moon. Combined with the brightness of the sport arena’s floodlights, the RBB population in nearby rice fields congregated into large swarms.

On the other hand, the long dry spell followed by rainfall has triggered the armyworms to produce more eggs. These could hatch into million worms as one female armyworm can lay about 800 to 1000 eggs. As grasses begin to sprout and farmers begin to plant, armyworms, which love to eat green plants, thrive with the abundance of food during this time of the year.

Host plants

There are many host plants for armyworm but corn is the most palatable for them. While many plants can also host RBB, the bug likes rice most, hence the name. Majority of RBB species are not actually pests; most of them merely feed on dead matter. Out of the 11 species of RBB present in the Philippines, only three species are harmful to plants.

The BPI added that if armyworms attack rice plants during the tillering stage—when rice plants produce side shoots and multiple stems—recovery is possible. But if the worms attack during booting stage—when rice plants develop flowers—there may be a 100% yield loss.

In the case of the RBB, rice crops can still survive if the bugs attack during the tillering stage in a low population density. However, if the bugs attack during reproductive stage—for example, at dough stage when green grains turn to yellow—a 60% yield loss may happen.

Biopesticides vs inorganic pesticides

According to the BPI, most farmers who were trained on integrated pest management at the DA’s Regional Crop Protection Centers know how to handle the two pests; hence, infestations in some areas are already being managed by farmers themselves.

The BPI, in coordination with the DA Regional Crop Protection Centers, has been mass-producing Metharizium as a safer control agent against RBB. Metharizium has been tested to be effective when regularly applied in RBB-infested rice fields. The biopesticide is now distributed to farmers throughout the country.

For armyworm, the BPI said that sanitation is the first strategy to avoid the pest, followed by synchronous planting. After harvest, all stubbles or straws in infested areas must be plowed under the ground to kill the remaining population of the pests. Lastly, on the onset of attack, spraying of NPV would be needed to kill the feeding worms.

The BPI likewise shared that experience in Palawan where the first RBB outbreak had occurred showed that spraying inorganic pesticides to RBB would also kill its natural enemies, as well as beneficial insects. Hence, the BPI is advising farmers to avoid spraying inorganic pesticides to control RBB.

The bureau is also advising farmers who have problems on RBB to practice intermittent irrigation. From time to time, the rice field must be drained then later flooded in a day to kill RBB nymph and eggs.

The BPI also recommends herding ducks on paddies when the rice plants have already stabilized. This will further help in managing the population of RBB. Insect proteins are of high quality and experience of farmers in China show that ducks feeding on RBB weigh heavier and have better meat quality.

DA Secretary Proceso Alcala called on farmers to promptly report infestations to their local agriculturists or to Regional Crop Protection Centers so that appropriate measures for effective pest management or eradication can be immediately implemented, hence reducing yield losses. (Jan P. Dacumos, DA-AFID)

Posted By: Lynne Pingoy


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