In this fact sheet we list the important biological control agents (BCAs); how to attract and conserve them, the risks from using different pesticides, and show how to maximise BCAs within an integrated pest management (IPM) framework.

Predatory insects: ladybird beetles; hoverflies (or syrphid flies); lacewings. Note, they:

• Reproduce in crops or in weeds nearby.
• Often eat many kinds of insects, whether pests or BCAs (i.e., they are polyphagous).
• Are continuously available from planting to harvest.
• Lay their eggs near pest prey.
• Differ according to the life stage that attacks pests. For some it is the adult, but for others it is the larva (or maggot), or both, i.e.:
  • Ladybird beetles (Photos 1&2): the adults and larvae eat other insects (see Fact Sheet no. 083).
  • Hoverflies (Photo 3): only the larvae (maggots) eat other insects; adults feed on nectar and pollen (see Fact Sheet no. 084).
  • Rove beetles (Photo 4): adults and larvae eat other insects.
  • Lacewings: green lacewings - only the larvae eat other insects, and the adults feed on nectar, pollen and honeydew; brown lacewings - adults and larvae eat other insects (as well as spider mites) (see Fact Sheets nos. 270 & 406).

Parasitic wasps (Photos 5-11, Diagram). Note, they:

• Usually they attack one or a few species of pests.
• Reproduce by female wasps laying eggs in or on bodies of host insects - eggs, larvae, pupae or adults. The eggs hatch and wasp larvae consume the host insect eventually killing it and forming pupae. Some species produce one pupa from a host, others produce many.
• Require nectar-producing plants; adult wasps need sugar resources to develop their eggs.
• Lay eggs inside larvae, pupae or adults of pests, depending on the species. They kill their prey and are called parasitoids. Some attack many different pests, e.g., Aphidius species prey on aphids, others are specialists with a very narrow host range, e.g., Cotesia vestalis preys on diamondback moth caterpillars. (See Fact Sheets nos. 287 & 285).

Spiders. Note, they:

• Are not insects; they have eight legs (Photos 12&13)
• Eat many types of insects (polyphagous), pests and other biocontrol agents.

• Conserve BCAs by avoiding broad-spectrum pesticides - synthetic pyrethroids, organophosphates and carbamates.
• There is no need to attract many of the important BCAs. Note the following:
  • Many BCAs move into crops very soon after crop germination, or when transplants are moved to the field.
  • Spiders and lacewing adults can be located in the middle of newly transplanted crops within 1-2 days.
  • Many BCAs use signals from plants that help them detect when crops are infested with their prey; for example:
    • Hoverfly and lacewing females can detect prey and will lay a small batch of eggs next to them.
    • Female parasitoid wasps can detect volatiles from damaged plants to attract them to chewing pests, such as caterpillars.
• If there is need to attract BCAs, do the following:
  • Grow flowering plants near crops, providing food sources (pollen and nectar) for hoverfly adults, parasitoid wasps, and pollinating insects. Note, it is probably best to limit this to brassica crops to avoid growing flowering plants that harbour thrips, polyphagous aphids and those aphids that spread viruses.
  • Plant grasses near vegetable crops to attract BCAs such as ladybird beetles and lacewings; they will be attracted initially by the grass aphids and other insects, and later spread to the vegetable crops. Note, grass insects are not likely to infest vegetable crops.

• Pesticides belong to several different chemical groups and so their impact on BCAs differs. Those that contain active ingredients that are toxic to a wide range of pests and non-target pests should be avoided, the so-called broad-spectrum insecticides.
• Impacts on bees must be considered for any product. Remember bees and parasitic wasps are in the same order, the Hymenoptera, so their reaction to any pesticide is likely to be similar.
• Also, consider the behaviour of BCAs. Many are on the foliage when sprays are applied, and also come into contact with residues after spraying as they move about the foliage.

A summary of the risks that pesticides present to parasitic wasps, bees and predators is given below (Table 1).

IPM consists of a number of linked actions which are most effective when coordinated by a Decision Pathway. The key components are as follows:

1. Scout crops:

• Careful, continuous observations in crops to:
  • Identify BCAs and pests present.
  • Carry out twice weekly surveys in tropical countries.
  • Assess increase/decrease in pest numbers and/or crop damage.

2. Identify infestations and record findings:

• After every scouting, summarise and record results:
  • Identify changes in infestations over time:
    • Record fresh damage.
    • Record crop growth stage.
    • Record over all health of the crop.

3. Assess RISKS:

• Stage of crop growth:
  • Seedlings - at high risk from virus vectors.
  • Leafy growth stage - relatively low risk from most pests.
  • Flowering stage - relatively high risk from flower thrips.
• Stage of pest life cycle:
  • Eggs and pupal stages - low risk (they cause no damage).
  • Small caterpillars - relatively low but increasing risk.
  • Large caterpillars - relatively higher risk.
  • Increasing numbers of high risk pests - increased risk.
• Wellness, weeds and weather:
  • Healthy plants with good nutrition and appropriate irrigation - low risk.
  • Weeds within a crop or nearby - increases risk.
  • Virus-infected plants adjacent to crop - high risk.
  • Cool weather - decreases risk from insect and mite pests (they develop and reproduce slowly).
  • Hot weather - increases risk from insect and mite pests (they develop and reproduce rapidly).
• Market:
  • A market that rejects or downgrades produce with minor pest damage - higher risk.

4. Make decision to Spray or Not-to-Spray (based on scouting results and risk assessment).

5. Choose pesticide (if decision is to Spray).

• Choose effective active ingredient to control target pest or pests:
• Low hazard to humans and animals.
• Low hazard to BCAs.

6. Assess history of local pesticide use:

• Rotate between different MoA groups if needed.
• Rotate between different MoA groups after 3-4 applications or 2-3 weeks of same pesticide.

7. Apply pesticide safely and effectively:

• Read the pesticide label.
• Check pesticide sprayer is operating correctly; check nozzle type.

8. Continue to scout crop:

• Assess:
  • Infestations.
  • Change of risks.
  • Efficacy of spray application.