Technical Bulletin #86: Integrated Pest Management – Natural Enemies and Biological Control of Insects

What are natural enemies? Natural enemies are insects that control other insect pests, and thus help regulate pest densities in nature, making cropping systems sustainable.

What types of beneficial insects can we find in nature? There are two types of beneficial insects: predators and parasitoids.

Predators simply eat other insects during one or more life stages of their life cycle, e.g. a ladybug or lady beetle eats aphids, caterpillar eggs, and small caterpillar larvae in its adult and larval stage. Normally, predators are not as specific as parasitoids in their host range, and may feed on a number of different insects.

Paper wasp with caterpillar prey Praying Mantis predator found in chili pepper

Cambodian Wasp Coleoptera Predator

Parasitoids are free living wasps or flies that lay their eggs on a specific prey. Larvae hatch inside that prey and feed on it internally, killing it, and giving birth to new parasitoid adults. Wasp parasitoids are more common than fly parasitoids.

[email protected] │ www.CambodiaHARVEST.org │ www.fintrac.com │ Technical Bulletin #86 │ June 2013 1 IPM: Natural Enemies and Biological Control of Insects Technical Bulletin #86 June 2013

Parasitoids are very susceptible to pesticides because they feed on flower nectars which contain no natural poisons, and are normally exposed to pesticides because they are active searchers.

Leaf miner parasitoid Parasitized melon worm

Parasitoids are targeted and attack only one stage of an insect life cycle. They are also specific in the number of different organisms that they parasitize. Normally a parasitoid only parasitizes one insect species, or at times the different species of one genus.

In nature it is common to find egg parasitoids, larval parasitoids, and pupal parasitoids. Parasitoids of nymphs or adults are less common because the insects are much more mobile during these life cycle stages.

How do I help maintain natural enemies in crops? Natural enemies have four basic needs: food, reproduction, a good living environment, and defense against strong winds and climatic conditions.

Plant biodiversity allows for the maintenance of diverse prey, flower nectar, and pollen for natural enemy survival. Cucurbit, solanaceous and malvaceaous crops (cotton, okra) bloom continuously and help maintain food sources for natural enemies.

At times, blooming plants that are attractive to wasps and flies are planted as reservoirs for natural enemies. Ideally, these plants should also have commercial value. Ideal plants are those that help maintain natural enemies and can either be sold as fresh flowers or spices, or have insecticide, nematicide, fungicide or bactericide properties. Special attention should be given to the fact that these reservoirs may maintain aphids, whiteflies and viruses at the same time. In such cases, the reservoir plant should be destroyed.

The use of live barriers of corn or sorghum also Cambodia HARVEST promotes the establishment of natural enemies. No. 46 Street 310 │ Sangkat, Beong Keng Kang 1 Khan Chamkamorn │ Phnom Penh, Cambodia Tel: 855 (0) 23 996419

This bulletin is made possible by the support of the American People through the United States Agency for International Development (USAID). The content is the sole responsibility of Fintrac Inc. and does not necessarily reflect the views of USAID or the United States Government.

[email protected] │ www.CambodiaHARVEST.org │ www.fintrac.com │ Technical Bulletin #86 │ June 2013 2