By JAMES TABABA
The previous article examined the mechanical and physical practices of pest control as a component of the Integrated Pest Management (IPM) approach. In part 4 of the Introduction to IPM, this article will explain the biological management practices for pest control.
The biological method of pest control is a component of Integrated Pest Management (IPM) which refers to the practices that involve plant repellents and pest reduction using pests’ natural enemies, such as predators, parasitoids, and diseases against them. This method utilizes the laws of nature that every organism in the environment has a natural predator. If there is a population increase in insect pests, it naturally attracts their natural enemies. However, with the use of chemical pesticides, these natural enemies of pests are also killed in the process. That is another reason to reduce or eliminate the use of pesticides.
There are three categories of natural enemies of insect pests – predators, parasitoids, and pathogens. These are called biological control or Biocon agents.
Predators are living organisms that naturally feed on insects. They can be birds, spiders, reptiles, fish, insects, or any animals that eat insect pests. Most of these animals usually eat insects, and they rarely focus on pests. However, insect predators have a smaller range of food targets which is why they are usually used in biological control methods. Predators used in pest controls are reared in the laboratory in preparation for mass release in the field.
In the Philippines, earwigs are used to control Asian corn borers. Earwigs are easily identified insects because of their pincer-like appendage called cerci. They feed on egg masses, larvae, and pupa or Asian corn borers.
Parasitoids are insects that lay their eggs inside other insect pests. The egg hatches into the body of the insect pest and kills it in the process. Most parasitoids have specific target insects. That is why they are also used as a biocon agent. Similar to the pest predators, parasitoids are also reared in the laboratory for mass release in the field.
A wasp-like parasitoid Comperiella sp was used to control the outbreak of the coconut scale insect, also known as ‘cocolisap.’ Cocolisap damaged more than two million coconut trees in CALABARZON.
Another widely known parasitoid wasp used to control pests in the Philippines is the Trichogramma. Trichrogramma is released in the field to control corn borer, tomato fruit fly larvae, sugarcane borer, eggplant borer, and cacao pod borer.
Pathogens are fungi, bacteria, or viruses that cause diseases in pests. One advantage of using pathogens as a biocontrol agent is that they can thrive in the environment and stay there for a long time as long as there are active pests in the area. One example of a pest pathogen is Bacillus thuringensis. Bacillus thuringensis is a bacteria that produces a toxin that destroys the midgut of insects.
Aside from biocon agents, use of natural pest repellent is a form of biological control practice. Neem, makabuhai, tubli, lagundi, and marigold are the common local Philippine plants used to make natural insect pest repellants.
For biological pest control methods to be effective, chemical pest control should not be applied. Pesticides will kill the natural enemies of pests. If pesticide use cannot be avoided, careful timing of application should be done to avoid the contact of pesticides with beneficial insects.
Introduction of new natural enemies should be carefully done because it may be an invasive species that may cause disruption of the natural ecosystem causing more harm than good. This also applies to the use of pathogens to control pests because these may also kill non-pest organisms.
One limitation of using parasitoids and predators is that they tend to move out of the cropping area if they have no longer food to eat. The use of natural predators may be more effective in greenhouses where they cannot escape.
The next article will explain the responsible use of chemical methods of pest control in IPM.