01 / 21

Integrated Pest
Management

A sustainable, science-based approach to controlling pests that minimizes environmental harm while maintaining effective crop protection.

AP Environmental Science

What Is a Pest?

A pest is any organism that causes economic damage, transmits disease, or competes with humans for resources. Pests include insects, weeds, fungi, rodents, and microorganisms. Not every organism in an ecosystem is a pest: the label depends on context and threshold levels.

Insects
Aphids, locusts, and boll weevils that destroy crops
Weeds
Invasive plants that out-compete crops for water and nutrients
Pathogens
Fungi, bacteria, and viruses that cause plant diseases

The Problem with Pesticides

Conventional pest control relies heavily on synthetic chemical pesticides. While effective in the short term, overuse creates serious environmental and health consequences that accumulate over time.

1
Pest resistance: Repeated exposure selects for resistant individuals, reducing pesticide effectiveness over generations.
2
Bioaccumulation: Pesticides concentrate as they move up trophic levels, harming top predators (e.g., DDT and eggshell thinning in raptors).
3
Non-target species: Broad-spectrum pesticides kill beneficial organisms like pollinators and natural predators.
4
Water contamination: Runoff carries pesticide residues into groundwater, streams, and aquatic ecosystems.

What Is Integrated Pest Management?

Integrated Pest Management (IPM) is a sustainable, ecosystem-based strategy that combines multiple control methods to manage pest populations below economically damaging levels while minimizing risks to people, property, and the environment.

The Economic Threshold

Two critical concepts drive IPM decision-making: the Economic Injury Level (EIL) and the Economic Threshold (ET).

Pest Population Time EIL ET Action Population curve Economic Injury Level Economic Threshold

The IPM Control Pyramid

Cultural Controls Crop rotation, resistant varieties, sanitation Biological Controls Natural predators, parasitoids, pathogens Mechanical Traps, barriers, hand-picking Chemical Last resort Increasing toxicity First resort

Cultural Controls

Cultural controls modify the growing environment to make it less favorable for pests. These are preventive, low-cost, and foundational to any IPM program.

Crop Rotation
Alternating crops disrupts pest life cycles by removing their preferred host plants each season.
Resistant Varieties
Planting cultivars bred for pest resistance reduces vulnerability without any chemical input.
Sanitation
Removing crop debris, infected plants, and weed hosts eliminates pest breeding sites.

Biological Controls

Biological control uses living organisms to suppress pest populations. It leverages natural predator-prey and parasite-host relationships already present in ecosystems.

1
Predators: Ladybugs consume aphids, lacewing larvae eat mites and whiteflies.
2
Parasitoids: Parasitic wasps lay eggs inside pest larvae, killing them as the wasp develops.
3
Microbial agents: Bacillus thuringiensis (Bt) produces toxins lethal to specific caterpillar species but harmless to other organisms.

Mechanical & Chemical Controls

Mechanical / Physical
Physically removing or excluding pests: traps, row covers, sticky boards, hand-picking, tillage, and barriers that prevent pest access to crops.
Chemical (Last Resort)
When other methods are insufficient, IPM uses the most targeted, least toxic pesticide available: narrow-spectrum over broad-spectrum, applied at precise timing and dosage.

Control methods act at different points in pest ecology

Crop mesh,parasitoid-caterpillar interaction and directed pest treatment in a cabbage setting.Pest controls can interrupt host availability, exclude pests physically, use natural enemies, or apply a directed treatment. Effective choices depend on the pest, host, timing and non-target effects.

Pest controls target different mechanisms

Pest controls target different mechanisms. Pest controls can interrupt host availability, exclude pests physically, use natural enemies, or apply a directed treatment. Effective choices depend on the pest, host, timing and non-target effects.Pest controls can interrupt host availability, exclude pests physically, use natural enemies, or apply a directed treatment. Effective choices depend on the pest, host, timing and non-target effects.

IPM vs. Conventional Pest Control

IPM Conventional
Goal Manage below economic threshold Eliminate all pests
Primary tool Multiple integrated methods Chemical pesticides
Timing Action at ET Calendar-based spraying
Environmental impact Low High
Resistance risk Low (varied tactics) High (single-mode selection)
Cost over time Decreases Increases (pesticide treadmill)

How to Apply IPM: Step by Step

1
Identify the pest. Accurate identification prevents wasted effort on the wrong organism and avoids harming beneficial species.
2
Monitor and scout. Regularly sample pest populations using traps, visual surveys, and field data to track population trends.
3
Compare to thresholds. Is the population at or approaching the Economic Threshold? If not, continue monitoring.
4
Select control methods. Choose the least disruptive method first: cultural → biological → mechanical → chemical.
5
Evaluate results. Assess whether the treatment was effective and adjust the plan for the next cycle.

Example: Apple Orchard IPM

An apple grower notices codling moth larvae damaging fruit. Let's walk through the IPM decision process.

1
Identify: Codling moth (Cydia pomonella) confirmed via pheromone trap captures.
2
Monitor: Pheromone traps show 15 moths per trap per week — above the ET of 10.
3
Cultural: Sanitation: remove fallen, infested apples that harbor larvae.
4
Biological: Release Trichogramma wasps that parasitize codling moth eggs.
5
Mechanical: Install cardboard trunk bands to trap pupating larvae.

Example: Rice Paddy IPM in Southeast Asia

Brown planthoppers (Nilaparvata lugens) are devastating rice crops. Farmers had been spraying broad-spectrum insecticides, which killed natural predators and caused pest resurgence.

Before IPM Broad-spectrum spraying ✕ Kills predators ✕ Pest resurgence ✕ Resistance develops ✕ Higher costs each year Yield loss: 30-50% After IPM Integrated approach ✓ Spiders eat planthoppers ✓ Resistant rice varieties ✓ Synchronized planting ✓ 60% pesticide reduction Yield increase: 10-15%

Why IPM Matters: Bioaccumulation

Persistent pesticides bioaccumulate through food chains. At each trophic level, the concentration increases by a biomagnification factor.

Water 0.003 ppm Zooplankton 0.03 ppm Small Fish 0.3 ppm Large Fish 3 ppm Top Predator 30 ppm 10,000x Trophic Level →

Common Mistakes on the AP Exam

✕ IPM Eliminates All Pests
IPM manages pests below the economic threshold, not to zero. Complete elimination is neither the goal nor ecologically desirable.
✕ IPM Uses No Chemicals
IPM allows chemical pesticides as a last resort. It minimizes their use but does not ban them entirely.
✕ Confusing EIL and ET
The ET is the action trigger (before damage occurs). The EIL is the damage point. Action at the ET prevents reaching the EIL.

IPM Control Methods Summary

Method Examples Advantages Limitations
Cultural Crop rotation, resistant varieties Low cost, preventive Slow, requires planning
Biological Ladybugs, parasitoid wasps, Bt Self-sustaining, specific Slow to establish, variable
Mechanical Traps, barriers, hand-picking No chemicals, immediate Labor-intensive, small scale
Chemical Targeted, narrow-spectrum pesticides Fast, effective Resistance, non-target harm

Question 1 of 5

What is the primary goal of Integrated Pest Management?

Question 2 of 5

A farmer notices aphid populations in her lettuce field. She releases ladybugs to prey on the aphids. Which type of IPM control is she using?

Question 3 of 5

What is the relationship between the Economic Threshold (ET) and the Economic Injury Level (EIL)?

Question 4 of 5

If a pesticide enters a lake at 0.005 ppm and biomagnifies by a factor of \( \times 10 \) at each of three trophic levels, what is the concentration in a tertiary consumer?

Question 5 of 5

Which of the following best explains why broad-spectrum pesticides can cause pest resurgence?