Understanding Biopesticides

Biopesticides are certain types of pesticides obtained from natural materials such as animals, plants, bacteria, and certain minerals.

Biopesticides are used as safer alternatives to controlling pests and are often part of integrated pest management programmes. Get to know the different type of biopesticides, their advantages and disadvantages and when to apply them in your home garden.

Types of Biopesticides
1) Microbial biopesticides and other entomopathogens
These consist of microorganisms (e.g. fungus, bacteria, nematodes, virus or protozoa) as the active ingredient that controls several kinds of pests.

Depending on the active ingredient, the microbial biopesticide is mass-produced and formulated to control a relatively specific target pest. Being living microorganisms, these biopesticides must be stored and applied in ways that preserve their viability.

2) Biochemical pesticides
These are derived from naturally occurring substances that control pests by non-toxic mechanisms. These include substances that disrupt the mating or molting processes and food-finding behaviors of pests.

Biochemical pesticides may also come from various plant extracts that attract or control the pests. Insect sex pheromones, other semiochemicals, plant bioactive compounds (botanicals), and natural insect growth regulators are common examples of biochemical pesticides.

Insect sex pheromones and semiochemicals

3) Plant-Incorporated Protectants (PIPs)
These are pesticidal substances that plants produce from genetic material that has been added to the plant. The genetically modified plants or organisms (GMO) manufacture the substance that destroys or controls the pest. Bacillus thuringiensis (Bt) corn is a GMO corn that produces proteins that are toxic to certain insect pests but not to humans, pets, livestock, or other animals.

Bacillus thuringiensis (Bt) GMO corn

• Less toxic than conventional pesticides
• Affect only the target pest and closely-related organisms while conventional pesticides may affect different insects, birds and mammals
• As an integral part of Integrated Pest Management (IPM) programs, it significantly reduces the use of conventional pesticides, while crop yields remain high
• The risk of pests and disease developing resistance is often considered to be low
• Effective in very small quantities and often decompose quickly, resulting in lower exposures and environmental residues
• Zero or low re-entry and handling interval
• Some microbial biopesticides can reproduce on or near to the target pest or disease, giving some self-perpetuating control
• Useful as second line of defense or supplementary treatment

• Slow acting and not a “quick kill’ when compared to conventional pesticides
• Lower efficacy and shorter persistence as compared to conventional pesticides
• Highly susceptible to adverse environmental conditions
• Grower or farmer requires greater level of knowledge to effectively use the biopesticides

Application of biopesticides
Biopesticides are mostly applied by spraying or drenching, dusting or as granules depending on the disease or pest being targeted. The success of insect sex pheromones and semiochemicals as biopesticides depends on the trap design and size. It is also dependent on the behaviour of the target pests.

Usually a pheromone-impregnated lure is placed in the commonly-used traps such as yellow sticky trap, delta trap, water-pan trap, bottle trap, or funnel trap. These traps are used to monitor the pest populations by sampling so as to trap and destroy adult pests.

Generally, in order to use biopesticides effectively and safely, growers should have an indepth knowledge about managing the target pest and must follow the manufacturer’s label directions carefully. This means it is important that growers select the right biopesticide for the right target pest and apply it at the right time, using the right method to ensure its effectiveness.

Learning More
If you are a gardening newbie, visit NParksSG, our refreshed YouTube Channel that serves as a one-stop repository for some 300 video resources. It covers topics ranging from types of soil needed for your garden and how to plant, harvest and even cook your edibles.

Learn more NParks’ Plant Health Services whose work helps keep Singapore safe from the incursion of exotic plant pests.

For more information about the flora and fauna found in Singapore, please visit Flora and Fauna Web.

If you like what you read, follow us on Facebook, Instagram and Telegram to get the latest updates.

Text from Plant Science and Health Branch