AP® Environmental Science review sheet from Aim for Five (aimforfive.com/enviro/units/5/5-14)
Unit 5 · Topic 5.14
5.14 Integrated Pest Management
Integrated pest management (IPM) combines several methods, like monitoring pests, natural predators, crop rotation and intercropping, and uses chemical pesticides only when needed. It reduces the risks pesticides pose to wildlife, water and people, but it takes more knowledge, time and planning.
Key terms
- integrated pest management (IPM)
- biocontrol
- crop rotation
- intercropping
What IPM is
Integrated pest management is an approach that uses many tools together to keep pests below the level where they cause serious economic damage. The goal isn't to wipe out every pest, which is often impossible and leads to resistance, but to manage them. Chemical pesticides are a last resort, used in targeted ways only when other methods aren't enough.
IPM starts with monitoring: farmers regularly check fields to identify which pests are present and how many. They act only when pest numbers reach an action threshold, the point where the cost of damage would exceed the cost of controlling it.
IPM methods
- Biocontrol: using a pest's natural enemies, like ladybugs to eat aphids, parasitic wasps that lay eggs in caterpillars, or bacteria that infect specific insects.
- Crop rotation: changing what's planted in a field from season to season. Pests that depend on one crop, such as insects whose larvae feed on corn roots, find no food when the field switches to a different crop, so their life cycle is broken.
- Intercropping: growing two or more crops together in the same field. A mix of plants makes it harder for pests that specialize on one crop to find and spread through it, and some plants repel pests or attract beneficial insects.
- Physical and mechanical controls: traps, barriers, row covers and removing infested plants.
- Resistant varieties: planting crops bred to resist certain pests or diseases.
- Targeted chemicals: when needed, using the least toxic, most specific pesticide, applied only where and when it's needed.
Benefits and drawbacks
| Benefits | Drawbacks |
|---|---|
| Less pesticide in water, soil and food | Takes more time to monitor fields |
| Fewer harmful effects on pollinators, birds and other non-target species | Requires knowledge and training about pests and their life cycles |
| Slows the evolution of pesticide resistance | Can cost more upfront; benefits come over time |
| Lowers pesticide costs over time and protects farmworkers' health | Results can be less immediate than spraying |
Biocontrol must be done carefully
Introducing a new species to control a pest can backfire if the new species becomes invasive. In 1935, cane toads were brought to Australia to eat beetles that damaged sugarcane. The toads didn't control the beetles well, but they spread across much of northern Australia and poisoned many native predators that tried to eat them. Today, biocontrol agents are tested to make sure they target only the pest before they're released.
Worked examples
Try each one yourself first, then open the solution.
- Example 1
Using an action threshold
A farmer's IPM plan says to treat for aphids only if scouting finds an average of more than 50 aphids per plant. Scouts count 30, 70, 45, 60 and 35 aphids on five plants. Should the farmer spray? If not, what should the farmer do?
Show the solutionHide the solution
- Step 1: Average = (30 + 70 + 45 + 60 + 35) ÷ 5 = 240 ÷ 5 = 48 aphids per plant.
- Step 2: 48 is below the threshold of 50, so spraying isn't justified yet.
- Step 3: Under IPM, the farmer keeps monitoring, encourages natural enemies like ladybugs, and treats only if numbers pass the threshold, choosing a targeted method first.
Answer: No. The average is 48 aphids per plant, below the threshold; the farmer should keep monitoring and rely on natural enemies.
- Example 2
A biocontrol trap
A farmer proposes importing a predatory beetle from another continent to control a crop pest. Describe one possible risk and one way to reduce it.
Show the solutionHide the solution
- Step 1: Risk: the beetle might become invasive. With no natural predators in its new home, it could spread and eat native insects (including beneficial ones) instead of, or as well as, the pest, as happened with cane toads in Australia.
- Step 2: Reducing the risk: test the beetle first to confirm it feeds only on the target pest, or use a predator already native to the area.
Answer: Risk: the beetle could become invasive and harm native species. Reduce it by testing that it targets only the pest, or by using a native predator.
Common mistakes
- Saying IPM never uses pesticides. IPM uses them as a targeted last resort.
- Describing IPM as only biocontrol. It combines several methods, starting with monitoring.
- Forgetting IPM's drawbacks. It requires more knowledge, labor and planning.
On the exam
- Questions often ask you to describe an IPM method and explain how it reduces pest damage or pesticide use. Be specific about the mechanism, like breaking a pest's life cycle.
- Expect to give one benefit and one drawback of IPM compared with routine spraying.
Connected topics
Videos
Check yourself
4 questions on 5.14 Integrated Pest Management. Pick an answer to see if you got it, and why.
Which is a disadvantage of integrated pest management compared with spraying a broad-spectrum pesticide on a fixed schedule?
In 1935, cane toads were brought to Australia to eat beetles that damaged sugarcane. The toads did little to control the beetles, spread across much of the continent and poisoned many native predators that tried to eat them. This case best illustrates which risk of pest control?
Corn rootworm beetles lay their eggs in cornfields in late summer, and the larvae that hatch the next spring survive almost only on corn roots. How does rotating corn with soybeans help control this pest?
| Years of spraying | Beetles surviving a standard dose (%) |
|---|---|
| 1 | 2 |
| 3 | 9 |
| 5 | 31 |
| 7 | 64 |
Hypothetical data from a potato farm that sprayed the same pesticide each year
Which strategy would most likely slow the further spread of resistance?
0 of 4 answered