Integrated pest management
What integrated pest management is, why it replaced calendar spraying, its building blocks from prevention to pesticides, and how it works on a real farm.
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Integrated pest management (IPM) is an approach to protecting crops that combines every suitable method, biological, cultural, physical and chemical, to keep pests below the level that causes economic harm, while keeping risks to people and the environment as low as possible. It treats pesticides as one tool among several, used when monitoring shows they are needed, not as a routine.
IPM is the official basis of plant protection policy in many countries and in international guidance from FAO and WHO. It is a central topic in entomology, plant pathology and agronomy exams, usually as an essay on its principles and components.
Why IPM was needed
After the Second World War, cheap synthetic insecticides made calendar spraying (spraying on a fixed schedule whether or not pests were present) the norm. Within two decades its problems were obvious; they are still the textbook case for IPM, often called the pesticide treadmill:
- Resistance: pests evolved resistance to one product after another, so more sprays and new chemicals were needed.
- Resurgence: spraying killed natural enemies along with the pest, so pest numbers bounced back higher than before.
- Secondary pest outbreaks: species that had been kept in check by natural enemies became pests once those enemies were gone. Spider mites and whiteflies are common examples.
- Residues and harm to farm workers, consumers, pollinators, birds, fish and water.
- Rising costs with falling returns.
In 1959, Stern, Smith, van den Bosch and Hagen proposed "integrated control": combining biological and chemical control, guided by economic thresholds. It broadened into IPM in the 1970s.
A frequently cited case is the brown planthopper in tropical Asian rice in the 1970s and 1980s. Heavy insecticide use killed the spiders and other predators that normally controlled it, causing severe outbreaks and the virus diseases it carries. Programmes that cut insecticide use, used resistant varieties and trained farmers to recognise natural enemies brought outbreaks under control, and they helped launch the farmer field school method of extension.
The definition
FAO and WHO's International Code of Conduct on Pesticide Management (2014) defines IPM as the careful consideration of all available pest control techniques and the integration of appropriate measures that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and reduce or minimise risks to human and animal health and the environment. It emphasises the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms.
Three ideas sit behind that sentence: prevent first, decide with information, and intervene with the least disruptive effective method.
The building blocks
1. Prevention: grow a crop pests find hard to exploit
- Resistant and tolerant varieties, the cheapest and most compatible tool. Host plant resistance works through antibiosis (the plant harms the pest's survival or growth), antixenosis (the plant is unattractive for feeding or egg-laying) and tolerance (the plant yields despite the pest). Insect-resistant genetically engineered crops are used in some countries, managed with refuges to slow resistance.
- Cultural practices: crop rotation, adjusting sowing dates to escape peak pest periods, destroying crop residues and volunteer plants, clean seed and planting material, balanced fertiliser (excess nitrogen makes many crops more attractive to sucking pests), proper spacing and irrigation.
- Habitat management: field margins, flowering strips and hedges that shelter natural enemies; intercrops and trap crops. The push–pull system intercrops maize with a repellent legume and borders it with an attractive grass, so stemborer moths are pushed away from the crop and pulled to the border.
- Quarantine and phytosanitary measures that keep new pests out.
2. Monitoring and decisions
- Scouting: regular, systematic counts of pests, damage and natural enemies.
- Traps: pheromone, light, coloured sticky traps.
- Forecasts: degree-day and weather-based models for pests and diseases.
- Decision thresholds: the economic threshold, the pest density at which to act so that the population does not reach the economic injury level.
Without monitoring there is no IPM: the decision to intervene must rest on what is actually in the field.
3. Non-chemical intervention
- Biological control:
- Conservation of the natural enemies already present, by avoiding broad-spectrum sprays and providing habitat;
- Augmentation: releasing reared natural enemies, such as Trichogramma egg parasitoids against moth pests, or predatory mites in greenhouses;
- Classical biological control: introducing a natural enemy from a pest's region of origin against an invasive pest. The vedalia beetle introduced against cottony cushion scale in California citrus in 1888–89 was the first great success.
- Biopesticides: microbial products based on bacteria (such as Bacillus thuringiensis), fungi, viruses and nematodes, and botanical products.
- Behavioural control: pheromones for mating disruption and mass trapping; attract-and-kill.
- Physical and mechanical: nets, row covers, barriers, hand-picking, sticky bands, light traps, solarisation, and in storage, hermetic bags and temperature control.
4. Chemical control, when justified
When monitoring shows a threshold has been reached and other measures are not enough:
- Choose selective products that spare natural enemies and pollinators where possible.
- Rotate modes of action, using the IRAC (insecticides), FRAC (fungicides) and HRAC (herbicides) classifications, to slow resistance.
- Apply only where needed: spot or band treatments, seed treatments where justified, correct dose and timing.
- Follow the label, re-entry and pre-harvest intervals. Registrations differ by country and change over time; use only products approved locally.
- Protect people and water: protective equipment, calibrated sprayers, buffer zones.
IPM in practice: an example
A season of IPM in a vegetable crop
A smallholder grows cabbage, attacked mainly by the diamondback moth, a pest notorious for resistance to many insecticides.
- Before planting: rotate away from brassicas; plant healthy seedlings raised under netting; destroy old crop residues; plant a border of a flowering crop to support parasitic wasps; consider a trap crop of an even more attractive brassica.
- Monitoring: twice a week, examine a fixed number of plants on a zigzag walk across the field and record larvae per plant and the proportion of plants infested; check pheromone traps for moth flights.
- Decision: use the locally recommended action threshold. When counts stay below it, do nothing except keep scouting; parasitoids may be keeping the pest in check.
- First intervention: if the threshold is reached, use a Bacillus thuringiensis product, which is selective and spares most natural enemies.
- If chemicals are needed: choose a product from a different IRAC group from the last one used, and do not repeat the same group in successive generations of the pest.
- Record and review: note what was found, what was done and the result, to adjust next season.
Compared with weekly calendar spraying, such programmes commonly cut the number of insecticide applications substantially while maintaining yield, with lower costs and less resistance.
Making IPM work
IPM is knowledge-intensive. It needs farmers who can recognise pests and natural enemies, reliable thresholds for local conditions, available biological products and resistant varieties, and advice that is independent of product sales. Farmer field schools, in which groups of farmers study a field through a season, have been widely used to build these skills across Asia, Africa and Latin America. Digital tools increasingly support scouting, identification and forecasting.
Key points
- IPM combines biological, cultural, physical and chemical methods to keep pests below economic levels with the least risk to health and environment.
- It arose from the failures of calendar spraying: resistance, resurgence, secondary pests, residues and cost.
- Its logic: prevent first, monitor, decide with thresholds, intervene with the least disruptive effective method.
- Host plant resistance works by antibiosis, antixenosis and tolerance.
- Biological control can be conservation, augmentation or classical.
- When chemicals are used: selective products, rotated by IRAC, FRAC or HRAC mode of action, applied only where needed, and only those approved locally.
What the exams ask
- School-leaving and entrance papers: the meaning of IPM, its components, and examples of cultural, biological and chemical control.
- Degree and research-fellowship entrances: the history (integrated control, pesticide treadmill), economic thresholds, types of biological control and host plant resistance, resistance management by mode of action.
- Professional and civil-service examinations: designing an IPM programme for a crop, farmer field schools and extension, and pesticide policy.
Described in general terms: the kind of examination, not a past paper. Laisha never reproduces exam questions.
Questions people ask
Does IPM mean no pesticides?
No. It means pesticides are used only when monitoring shows they are needed, chosen to do the least harm, and combined with other methods. Organic farming, by contrast, restricts the kinds of products allowed.
Is IPM more profitable than routine spraying?
In many studies, yes: fewer sprays cut costs while yields hold. But it needs time for scouting and knowledge of pests and natural enemies, which is why training and advice matter.
Why do natural enemies matter so much?
They suppress many potential pests continuously and for free. Broad-spectrum sprays that kill them can turn minor pests into major ones, the resurgence and secondary-outbreak problem.
Sources
- FAO and WHO. The International Code of Conduct on Pesticide Management. Food and Agriculture Organization of the United Nations and World Health Organization, 2014.
- Stern, V. M., Smith, R. F., van den Bosch, R. and Hagen, K. S. "The integrated control concept." Hilgardia 29, 81–101 (1959).
- Kogan, M. "Integrated pest management: historical perspectives and contemporary developments." Annual Review of Entomology 43, 243–270 (1998).
- Khan, Z. R. et al. "Push–pull technology." International Journal of Agricultural Sustainability 9, 162–170 (2011).
- IRAC. Mode of Action Classification Scheme. Insecticide Resistance Action Committee, updated regularly.
- Dent, D. and Binks, R. H. Insect Pest Management, 3rd edition. CABI, 2020.
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