PAMPANGA

Peña: Dragonflies and other natural pest control

E-ssue

HEALTH Secretary Francisco Duque III recently declared a National Dengue Alert due to the rapidly increasing number of cases observed in several regions. Just last Wednesday, I visited my friend’s daughter who was confined in the hospital due to dengue. According to her, this is the third time that she got the disease.

This means there are mosquitoes in our midst carrying at least three out of the four serotypes of dengue virus.

The DOH recommends the usual countermeasures: eliminate potential breeding habitats such as pails, flower pots and tires; wear protective measures like long sleeves and pants; use insect repellent and fogging if there is an impending outbreak.

As a long-term measure however, mosquitoes like the dengue-carrying Aedes aegypti can be controlled using Mother Earth’s natural law: the predator-prey relationship. In an ecosystem, a species thrives when there is an absence of a predator. In this case, the mosquitoes as prey, and dragonflies as predators.

Dragonflies are predators both in their adult and larval stage. Adult dragonflies eat mosquitoes, as many as 20 in an hour. Young dragonflies, called nymphs, live in water and eat mosquito larvae.

The town of Wells, Maine in the United States has been battling mosquitoes for many years by releasing Nymphs on fresh water ponds, marshes, swamps and other slow moving waterways. When they complete their metamorphosis and become adults, they continue to prey upon mosquitoes in large quantities.

Mosquitoes abound probably because of the lack of dragonflies and other predators. Have you noticed that the swarms of dragonflies that appear during dusk are gone? Maybe because their natural habitats like grassland were turned into concrete jungles and their breeding grounds are now polluted.

Bats are also mosquito predators. Individuals of some bat species can capture up to 1,000 mosquitoes in a single hour. I just don’t know if they are effective with the Aedes aegypti since it is a day-biting mosquito and bats usually roam at night.

Another natural pest control is the mosquito fish (scientific name: Gambusia affinis). Known locally in Pangasinan as “Itar” or “Tuyong” in Ilocano and “Katapa” in Tagalog. The American colonial government introduced the mosquito fish in the Philippines during the early 1900s as part of efforts to control the spread of malaria, according to Dr. Westly Rosario, head of the Bureau of Fisheries and Aquatic Resources (BFAR) National Integrated Fisheries Technology and Development Centre.

The DENR however warned against the rampant use of the mosquito fish since it is an alien invasive species. A DENR official said that the Philippines has native mosquito-eating animals like the tuko (gecko) and native gobies but there are now only a few of them.

While it’s true that the mosquito fish is invasive in nature, Dr. Rosario said it has been with us for so many decades and never became a problem and for an instance, a threat to the environment.


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