The basics of biological pest control

In the battle to protect crops and gardens, one of the most effective solutions isn't found in a spray bottle, it’s already crawling, flying, and living right in the ecosystem. Biological pest involves using nature’s own food web to manage pests safely and sustainably.

While chemical pesticides remain an important tool, many growers are discovering that nature already provides highly effective pest control through beneficial insects and predatory mites. The future of crop protection lies not in replacing every chemical product, but in using biology and chemistry wisely together.

An Integrated Pest Management approach, which is an ecosystem based pest management strategy, allows farmers to protect their crops, preserve beneficial organisms and improve long-term profitability. In this article we will discuss beneficial insects, bio-insecticides and beneficial nematodes which already exist naturally in a healthy ecosystem.

Part 1: Predatory insects and mites – Nature's pest

control team

Across Zambia, farmers face increasing pressure from insect pests that damage crops and reduce yields. Beneficial or predatory insects feed on crop pests and help keep their populations below damaging levels.

Adalia bipunctata, commonly known as the two-spot ladybird or the two-spotted ladybug, is a species of a predatory beetle. Photo: Koppert

What are predatory insects?

Predatory insects hunt, kill, and consume harmful pests throughout their lives. Unlike pesticides that stop working once sprayed, predators continue searching for food as long as pests are present. Some common beneficial predators include:

• Ladybird beetles that feed on aphids, mealybugs, and scale insects.

• Green lacewing larvae, often called "aphid lions", which consume aphids, whiteflies, thrips, and small caterpillars.

• Predatory mites that control spider mites and certain thrips species.

• Minute pirate bugs that attack thrips, mites, aphids, and insect eggs.

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Why are they beneficial?

Beneficial predators help farmers by:

• Reducing pest populations naturally.

• Lowering the need for repeated chemical spraying.

• Slowing the development of pesticide resistance.

• Protecting pollinators and other beneficial insects.

• Supporting a healthier farm ecosystem.

Anagyrus vladimiri is a parasitic wasp belonging to the Encyrtidae family. This parasitic wasp is particularly effective for mealybug control, a common pest affecting various crops. Photo: Koppert

Helping beneficial insects thrive

Growers can encourage beneficial insects by:

• Scouting crops regularly - to spot and manage pests before they spread too wide

• Spraying chemicals only when necessary - to reduce chemical residues that may remain on flowers, leaves and in soil

• Choosing selective products that are compatible with beneficial insects - as most insecticides may also kill off the beneficial insects

• Providing flowering plants around fields as food sources for adult beneficial insects.

• Preserving natural vegetation where practical - to provide a natural habitat for these insects to live and breed

Part 2: Bio-Insecticides – Natural protection for crops

Not every pest problem can be controlled by predators alone. When pest numbers increase rapidly, growers may need additional control measures. Bio-insecticides provide an effective option while remaining compatible with many biological control programmes.

What are bio-insecticides?

Bio-insecticides are products made from naturally occurring organisms or substances that target specific pests. Unlike many broad-spectrum chemicals, bio-insecticides usually affect only the target pest, leaving beneficial insects largely unharmed. Common examples include products based on:

• Naturally occurring bacteria. - e.g bacticillicus?

• Beneficial fungi - for example the beneficial fungi Akanthomyces muscarius effectively controls a range of insect pests, including whitefly, aphids and thrips.

• Plant extracts. - for example products containing neem extract from the Neem tree [Azadirachta indica] are becoming very popular in Zambia to treat fungus and aphids.

• Naturally produced insect toxins.

Leaves of a mature neem tree. Photo: Utsab Mahata / Pexels.com

How do bio-insecticides work?

Different bio-insecticides work in different ways. Some are eaten by caterpillars and stop them feeding, while others infect insect pests through their outer body or interfere with their normal development. Because they target specific pests, they are most effective when applied early, before pest populations become too large.

Advantages of bio-insecticides:

• Lower impact on beneficial insects.

• Reduced chemical residues on crops.

• Lower risk of pesticide resistance when used correctly.

• Suitable for Integrated Pest Management programmes.

• Improved worker safety compared with many conventional pesticides.

Successful use of these bio-insecticides depends on:

• Correct pest identification - insecticides are specific to specific pests

• Applying products at the right pest stage - these natural products target specific life phases of pests

• Good spray coverage - spraying widely increases the likelihood of direct contact

• Following label recommendations carefully - as each insecticide works differently

• Regular crop monitoring - to see if the treatment is working or reapplication is needed

Bio-insecticides are not always a quick knockdown solution, but when used correctly, they provide reliable pest control while protecting the farm's natural balance.

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Part 3: Beneficial nematodes and entomopathogenic fungi – Powerful allies beneath the surface

Many damaging crop pests spend part of their life cycle in the soil or hidden inside plants where conventional pesticides are difficult to reach. Beneficial entomopathogenic nematodes and fungi offer growers another natural tool to control these pests.

Beneficial entomopathogenic nematodes

Entomopathogenic nematodes are microscopic roundworms that actively search for insect pests in the soil. Once they find a suitable host, they enter the insect through natural body openings and release beneficial bacteria that quickly kill the pest. The nematodes then reproduce inside the insect before searching for new hosts. They can help control pests such as cutworms, white grubs, certain beetle larvae, caterpillars that pupate in the soil and other soil-dwelling insect pests.

Nematodes Photo: Koppert

Entomopathogenic fungi

Unlike nematodes, entomopathogenic fungi infect insects directly through their outer body. Their spores attach to the insect, germinate, and grow inside the pest, eventually killing it before producing new spores that can infect other susceptible insects. These fungi are commonly used against whiteflies, aphids, thrips, mealybugs, certain beetles and various caterpillar species.

These biological agents provide several long-term benefits:

• Reach pests hidden in the soil or plant canopy.

• Reduce reliance on chemical pesticides.

• Help delay pesticide resistance.

• Are generally safe for beneficial insects, people and the environment when used according to recommendations.

• Fit well into Integrated Pest Management programmes.

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Building a sustainable farming system

Biological control is most successful when different tools are used together. Predatory insects, bio-insecticides, beneficial nematodes and entomopathogenic fungi each play a different role in managing pests.

By combining these natural solutions with regular crop scouting, good crop hygiene and responsible pesticide use, growers can build healthier farms that are more productive, environmentally sustainable and better prepared for future pest challenges.