Pest and disease busters from the wild

Leaves with symptoms of citrus greening disease. (Photo by Tim Gottwald)

By Ronaldo T. Alberto

Plants from the wild defend crops from pest and diseases just as effectively as chemical pesticides without hurting the environment.

Substances derived from indigenous plants found in Central Luzon forests can protect crops from known pests and diseases, a research team from Central Luzon State University’s (CLSU) Institute of Climate Change and Environmental Management (ICCEM) found out. The team screened plant samples for their pesticidal properties. The CLSU researchers subsequently produced an affordable and environmentally-safe pesticide for farmers.

The increasing human population threatens the survival of the human race. More and more mouths have to be fed, while lands devoted to crops continue to shrink.

Although modern agriculture feeds the ballooning population, increased use of synthetic fertilizers and pesticides damage the environment.

Synthetic pesticides, though very effective, often result in the development of immunity of pests, killing of non-target organisms, and emergence of new pests.

Plant pests, an integral part of the agro-ecosystem, will be present in the field and continue to compete directly with farmers as long as there are crops. The only thing that could be done is to neutralize them to prevent losses. Approaches in pest control varies. But the use of pest control systems that are environment friendly, effective but less toxic to humans and non-target organisms is more preferred as consumer awareness on the hazards of using chemical pesticides increases.

Biopesticides are derived from natural materials: animals, plants, bacteria, and certain minerals. Biopesticides are a good alternative that should be explored in dealing with pests in the field. Naturally less toxic than conventional pesticides, biopesticides eliminate only the target pests and closely related organism. Biopesticides are effective even in small quantities and quickly decompose. Most commercial pesticides adversely affect other organisms like birds, insects, and mammals, and cause pollution. Biopesticides can lessen farmers’ dependence on conventional pesticides and still ensure high yield.

Botanicals or plant pesticides are naturally occurring substances from plant extracts with antimicrobial and pesticidal properties. Active substances are extracted from various plant parts: stem, seeds, flowers, leaves, and roots.

Plants are rich sources of organic compounds which are essential to life. They are capable of producing an overwhelming variety of low-molecular-weight organic compounds, called secondary metabolites, which have very unique and complex structures. Through metabolism, primary metabolites are further synthesized into secondary metabolites or natural products which provide defense against predators and interspecies competition, and facilitate the reproductive process.

Many of these compounds are found only in limited plant groups, with each plant species having a distinct profile of secondary metabolites with antimicrobial and pest repellant properties. Plant secondary metabolites are important for both plants (for plant-environment interactions) and humans (for biological activities with high therapeutic value) (Cannell, 1998).

In the lowlands, botanical pesticides or plant pesticides have long been used for combating plant diseases. These species possess active substances but vary with season growing condition, age of harvest, difference in extraction and storage methods. However, the indigenous flora in the mountains remains untapped.

The Philippines is known to have plants with medicinal and pesticidal substances which are becoming popular due to rising interest on safer food or medicine substitutes. In this program named “Integrated Research and Development Program on Biodiversity Assessment and Conservation of Selected Forest Ecosystems in Central Luzon”, native plants in the three forest ecosystems are studied to make botanical pesticides which can manage bacterial and fungal diseases in economically important crops and vegetables commonly grown in the region.

Out of the many collected plant samples and after series of laboratory tests, a number of plants turn out to be potential botanical or plant pesticides. Currently, there are screenhouse experiments to test the effectiveness of the formulated substances. The results will be validated after the field trials in the third quarter of 2015.

The discovery and development of these indigenous plants as botanical or plant pesticides will have a significant impact in the country’s agriculture. These can provide solutions to problems in growing organically-produced crops.

This appeared in Agriculture Monthly’s February 2019 issue. 

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