AP® Environmental Science · Unit 5 · Topic 5.14
Integrated Pest Management
Integrated pest management controls pests by monitoring populations, waiting until they cross a damage threshold, and relying on biological control first, spraying synthetic pesticide only as a last resort.
Integrated pest management, or IPM, treats pesticide as one tool among several rather than the default response. A farmer monitors fields regularly, counting pests or checking for damage, and compares what they find to a damage threshold: the pest level at which the economic cost of crop loss would exceed the cost of acting. Below that threshold, the farmer does nothing or relies on biological control, meaning predators, parasites, or pathogens that already attack the pest. Only when the population crosses the threshold does the farmer spray, and even then they aim to use the least disruptive option available.
This restraint is exactly why IPM can outperform routine spraying. A fixed weekly schedule kills pests, but it also kills the predators and parasitic wasps that would otherwise keep pest numbers down on their own. Spraying only at threshold events leaves those natural enemies alive most of the season, so they keep suppressing the pest population between treatments. Fewer sprays can mean fewer pests, not more, because the farm keeps its built-in control system intact. This is also why IPM is not organic farming with a new name: organic farming excludes synthetic pesticides entirely, while IPM keeps them in the toolkit and simply uses them sparingly and strategically.
IPM also slows the evolution of pesticide resistance, which connects it to the broader story of sustainable agriculture in this unit. Every spraying event is a selection pressure: resistant individuals survive and reproduce, so frequent spraying breeds resistant pest populations fast. Spraying only a few times a season, at real thresholds, reduces that selection pressure and keeps susceptible pests and natural enemies in the mix longer, extending the usefulness of the pesticides a farm still depends on.
Key terms
- Damage threshold
- The pest population level at which expected crop loss justifies the cost and risk of control action.
- Biological control
- Using a pest's natural predators, parasites, or pathogens to keep its population low.
- Pesticide resistance
- A heritable trait that lets some pests survive pesticide exposure, becoming more common with repeated spraying.
- Monitoring
- Regularly checking fields for pest numbers or damage instead of acting on a fixed schedule.
Watch it explained
- How it worksWalk me through monitoring, damage thresholds, biological control, and spraying as a last resort.
- How it worksHow does releasing a predator insect hold a pest population under the damage threshold?
- Common mistakeWhy isn't integrated pest management just organic farming under a different name?
- Going furtherWhat happens to pesticide resistance when spraying is cut back to threshold events only?
Check yourself
End of topic.