Unit 5 · Topic 5.14 Beta

Integrated Pest Management

Integrated pest management keeps pests below damaging levels by monitoring them, preventing outbreaks, and using biological, physical and cultural controls first and targeted pesticides only when counts pass an action threshold.

Practice 7: Environmental Solutions

Part 1 · Hook

Why this matters

In the 1980s, rice farmers in Indonesia were spraying insecticide again and again, and a pest called the brown planthopper kept getting worse: the sprays killed the spiders and other predators that ate it. The government cut its pesticide subsidies, banned dozens of insecticides on rice, and trained farmers in field schools to count pests and protect predators. Spraying fell sharply while rice yields held up.

Part 2 · Before you start

What this builds on

Part 3 · Prerequisite check

Quick check before you start

1. How does a pest population become resistant to a pesticide?

  1. Spraying kills susceptible pests, and resistant survivors breed
  2. Each pest gets used to the pesticide over its life
  3. The pesticide changes the pests' genes directly
  4. Pests learn to avoid sprayed plants and teach their young
Show the answer

Resistance is natural selection on existing variation.

  • Correct: Spraying kills susceptible pests, and resistant survivors breed:
  • Each pest gets used to the pesticide over its life:
  • The pesticide changes the pests' genes directly:
  • Pests learn to avoid sprayed plants and teach their young:

2. Why can spraying an insecticide make a pest problem worse?

  1. It kills the pest's predators too, so the pest rebounds
  2. It fertilizes the crop, so the crop grows faster
  3. It makes the crop taste better to pests
  4. It adds water to the soil, so pests multiply
Show the answer

Killing natural enemies removes a check on the pest.

  • Correct: It kills the pest's predators too, so the pest rebounds:
  • It fertilizes the crop, so the crop grows faster:
  • It makes the crop taste better to pests:
  • It adds water to the soil, so pests multiply:

Part 4 · See it

See it first

Line graph, invented data for practice. Average aphids per leaf, counted each week: 2, 3, 5, 8, 12, 6, 4, 5, 7 and 9 for weeks 1 to 10. A dashed line marks the action threshold at 10 aphids per leaf. The count passes the threshold only in week 5 (12 aphids per leaf); a targeted control is used then, and the count falls to 6 the next week and stays below the threshold.
Pests are counted every week, and control is used only when the count passes the action threshold. Invented data for practice. LevlPrep original diagram.

Part 5 · Step by step

How it works, step by step

  1. Farmers count pests regularly (monitoring)they know when pests are near a damaging level and when they are not
  2. Control is used only when pests pass an action thresholdfar less pesticide is sprayed than on a fixed schedule
  3. Less spraying and choosing narrow-acting methodspredators and pollinators survive and keep pests in check
  4. Fewer sprayings select less strongly for resistancethe pesticides that are used keep working longer

Part 6 · Key ideas

Key ideas

  • Integrated pest management (IPM) combines methods to keep pests below the level that causes real damage, using as little pesticide as possible.
  • Steps: monitor pests, set an action threshold, prevent problems (changing which crop grows in a field each year, resistant varieties, timing of planting), and control pests with the narrowest tool first.
  • Biological control uses natural enemies: ladybugs and lacewings eat aphids, tiny wasps lay eggs in caterpillars. Physical methods include traps, barriers and hand weeding.
  • Benefits: less pesticide, lower costs, less harm to nontarget species and water, slower resistance. Drawbacks: it takes knowledge, labor and time, and can be slower to act.

Part 7 · Misconception

A common mistake

The wrong idea: Integrated pest management means never using pesticides.

What actually happens: IPM uses pesticides as a last resort: only when monitoring shows pests above the action threshold, and then the most targeted product, in the smallest amount, at the right time.

Part 8 · Check yourself

Check yourself

Exam-style questions. Anything you miss goes into your review queue.

1. What is the main goal of integrated pest management?

  1. Keep pests below damaging levels with little pesticide
  2. Kill each pest on a farm with the strongest spray that is sold
  3. Grow crops with no monitoring of the pests in the fields
  4. Replace each pesticide with a stronger one each year
Show the answer

IPM aims to control damage, not to wipe out every pest, while limiting pesticide use.

  • Correct: Keep pests below damaging levels with little pesticide: Right: control below a damaging level, with little spraying.
  • Kill each pest on a farm with the strongest spray that is sold: Total elimination with strong sprays is the approach IPM moves away from.
  • Grow crops with no monitoring of the pests in the fields: Monitoring is the heart of IPM.
  • Replace each pesticide with a stronger one each year: Escalating sprays is the pesticide treadmill.

2. Why does IPM slow the evolution of pesticide resistance?

  1. Spraying less often selects less for resistance
  2. IPM sprays more often, so no pests survive to breed
  3. IPM uses one pesticide each year so pests are unable to adapt
  4. Natural enemies make the pests' genes change back
Show the answer

Fewer sprayings means less selection pressure, so resistant pests gain less advantage.

  • Correct: Spraying less often selects less for resistance: Right: less spraying, weaker selection.
  • IPM sprays more often, so no pests survive to breed: IPM sprays less, not more.
  • IPM uses one pesticide each year so pests are unable to adapt: Using one product repeatedly speeds resistance; IPM rotates methods.
  • Natural enemies make the pests' genes change back: Predators do not change pests' genes.

Model or diagram

Weekly pest counts on one farm

Line graph, invented data for practice. Average aphids per leaf, counted each week: 2, 3, 5, 8, 12, 6, 4, 5, 7 and 9 for weeks 1 to 10. A dashed line marks the action threshold at 10 aphids per leaf. The count passes the threshold only in week 5 (12 aphids per leaf); a targeted control is used then, and the count falls to 6 the next week and stays below the threshold.
LevlPrep original diagram.

3. In which week did the pest count pass the action threshold?

  1. Week 5
  2. Week 4
  3. Week 10
  4. Week 1
Show the answer

Week 5 had 12 aphids per leaf, above the threshold of 10.

  • Correct: Week 5: Right: 12 is above 10.
  • Week 4: Week 4 had 8, below the threshold.
  • Week 10: Week 10 had 9, below the threshold.
  • Week 1: Week 1 had 2.

4. Write the setup for the percent change in the aphid count from week 5 to week 6, after the targeted control, then give the answer.

Type the setup as on the exam, with brackets and units, then the answer.

Show the answer

6−1212×100=−50%\frac{6 - 12}{12} \times 100 = -50\%: the count halved.

  • Setup: 6−1212⋅100\frac{6 - 12}{12} \cdot 100; answer -50 %

5. A farm on a fixed schedule sprays every two weeks. How many sprayings would it make in these 10 weeks, compared with the IPM farm's one?

  1. 5 sprayings, compared with 1
  2. 10 sprayings, compared with 1
  3. 2 sprayings, compared with 1
  4. 1 spraying, the same as IPM
Show the answer

Every two weeks over 10 weeks is 102=5\frac{10}{2} = 5 sprayings; IPM sprayed once, in week 5.

  • Correct: 5 sprayings, compared with 1: Right: 10 ÷ 2 = 5.
  • 10 sprayings, compared with 1: That would be weekly spraying.
  • 2 sprayings, compared with 1: Every two weeks gives more than 2 in 10 weeks.
  • 1 spraying, the same as IPM: The fixed schedule sprays regardless of counts.

6. In weeks 7 to 10 the count rose again from 4 to 9. What should the IPM farmer do?

  1. Keep monitoring and act again if the count passes 10
  2. Spray right away because the count is rising
  3. Stop monitoring because the count is below 10
  4. Release a new pesticide each week to stop the rise
Show the answer

IPM acts on the threshold, not on any rise; at 9 the count is still below 10.

  • Correct: Keep monitoring and act again if the count passes 10: Right: watch and wait until the threshold.
  • Spray right away because the count is rising: A rise below the threshold does not call for spraying.
  • Stop monitoring because the count is below 10: Monitoring continues all season.
  • Release a new pesticide each week to stop the rise: Weekly pesticides are the opposite of IPM.

7. A farm used 24 kg of insecticide per hectare on a fixed schedule. After switching to IPM, it uses 30% of that amount. How many kilograms per hectare does it use now?

Type a number, then its unit (kg/ha). Scale words (2.5 million) and powers of ten (2.5 × 10^6) are read.

Show the answer

24kgha×30100=7.224\,\frac{\text{kg}}{\text{ha}} \times \frac{30}{100} = 7.2 kg per hectare.

  • Answer: 7.2 kg/ha

Part 9 · Summary

Summary

Integrated pest management keeps pests below damaging levels by monitoring them, preventing outbreaks, and using biological, physical and cultural controls first and targeted pesticides only when counts pass an action threshold. It cuts pesticide use, protects natural enemies, pollinators and water, and slows resistance, but it takes more knowledge, labor and time.

Part 10 · Up next

What comes next

Part 11 · Connections

Connections

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