Integrated Pest Management Basics: How IPM Works

What is integrated pest management and how does it differ from conventional control?

Conventional pest control tends to be reactive: a pest is seen, a spray is applied. That response can appear to work in the short term, but over time it carries several compounding costs. Under repeated chemical pressure pests develop resistance; populations of beneficial insects are damaged and natural balance is disrupted. The result is that growers face rising spray rates season by season, interrupted by population flare-ups that catch them off guard.

Integrated pest management (IPM) is a systematic framework designed to break that cycle. Its central distinction from conventional control is that management decisions are made in response to observation and data, not to the calendar or to the presence of any pest at all. While a population stays below a defined threshold, monitoring continues and no intervention is triggered; an intervention is introduced only when the population is crossing that threshold, and with the tool that fits the situation. The aim is not to eliminate chemical use but to move it to the end of the decision queue.

In our field work we see that growers who switch to an IPM approach invest more effort in record-keeping during the first season, then begin to see a clear difference in both cost and crop quality from the second season onward. Changing habits is the hard part; the numbers tend to point in the right direction once a season of data exists.

What are the four components of IPM?

IPM is not a single method but a hierarchy of four components that support one another. They are applied in order: lower-risk options first, more intensive interventions only when earlier ones prove insufficient.

First component: Monitoring and recording. Regularly recording pest species, population densities and timing is the foundation of every decision. There is no IPM without monitoring — knowing what is present and in what quantity is the prerequisite for deciding when to act.

Second component: Cultural and physical measures. Greenhouse hygiene, entry management, tool cleaning, irrigation timing and weed control are the primary barrier against pest multiplication. These are the cheapest and lowest-risk component; every other intervention is built on top of this foundation.

Third component: Biological control. Deploying natural enemies — parasitoid wasps, predatory mites, entomopathogenic fungi — suppresses pest populations without chemical use. Biological control performs best when cultural measures have already kept pest pressure low.

Fourth component: Chemical intervention. When monitoring data shows the economic threshold has been crossed and other measures are insufficient, a chemical product with an appropriate selectivity and safety profile is used as the last resort. In IPM, chemical application is not automatic; it is justified by data.

The four components reinforce each other when applied consistently. Skipping one, or reversing their order, removes what makes the system work.

Why is pest monitoring the non-negotiable first step in IPM?

When intervention decisions rest on a spray calendar rather than field observation, both cost and environmental impact accumulate unnecessarily. Monitoring is the data source that removes that waste. Before answering “when should I intervene?”, the prior question must be answered: “how many pests are present, and which way is the trend moving?”

The most practical monitoring tools in protected cropping are sticky cards. Yellow cards are most sensitive to whitefly, aphid and leafminer; blue cards are more selective for thrips. Cards are hung at fixed positions and counted at least once a week, with numbers recorded each time. A sharp rise — a noticeably higher count than the previous week — is an early signal of a building pressure wave. When that trend is spotted early, intervention can happen while the population is still low, meaning far less chemical or a smaller biological agent dose is needed. For step-by-step guidance on setting up and reading sticky cards, see our sticky trap monitoring guide.

Fixed-plant visual counts are an equally important part of monitoring. Specific plants are marked as sample plants and the pest density on the same plants is recorded at each count. This tracks trends far more reliably than random sampling. Keeping weekly records and plotting counts over time reveals seasonal patterns — “whitefly pressure climbs every year in early September” — that allow preventive action to be taken ahead of the spike and biological agents to be prepared in advance. Without trend data, none of that forward planning is possible; the grower stays reactive as the season progresses.

What role do cultural measures and hygiene play in IPM?

Cultural measures are the cheapest and lowest-risk layer of IPM. When they are in place, the layers above them — biological and chemical — have far less work to do. In a greenhouse where crop debris is not cleared on time, entry is not managed, and tools are not cleaned regularly, no amount of beneficial insect release will hold pest pressure at a manageable level for long.

The most important cultural measure is crop debris management. Most pests and pathogens overwinter or multiply in dead or diseased plant tissue. Collecting symptomatic leaves and shoots at least once a week and removing them from the greenhouse in sealed bags breaks that cycle. Entrance hygiene — a disinfectant mat, separate work clothing, a hand disinfection point — reduces the risk of pests being carried in from outside. Tool disinfection prevents disease from moving from plant to plant during pruning. For a full account of these practices and greenhouse-specific detail, see our greenhouse hygiene guide.

Irrigation management is part of cultural control as well: watering during the day, not leaving the leaf surface wet overnight, and dropping high humidity with early-morning ventilation all interrupt the cycle of Botrytis, powdery mildew and other fungal pathogens. Weed control is a component of IPM that is often underestimated; weeds inside the greenhouse and in a strip around its perimeter serve as alternative hosts for migratory pests such as thrips and aphid. Keeping that perimeter strip as bare soil or mulch removes the shelter.

How does biological control fit into an IPM system?

Biological control is the third component of IPM; it performs best when cultural measures have already kept pest pressure low. Under high pest density, released beneficials struggle to establish a balance — instead of suppressing the population they fall behind. Biological intervention should therefore be planned as a system component deployed at low pressure, not as an emergency measure at high pressure.

Biological control agents commonly used under cover include parasitoid wasps (Encarsia formosa, Aphidius spp.), predatory mites (Phytoseiulus persimilis, Amblyseius spp.) and entomopathogenic fungi (Beauveria bassiana, Isaria fumosorosea). Each agent is effective against specific pests; choosing the wrong one wastes both time and money. When monitoring data identifies the pest species correctly, agent selection becomes far more accurate. For detailed guidance on release timing, frequency and which agents can be combined, see our beneficial insect release programme guide.

Compatibility with chemicals is another critical factor in the effectiveness of biological agents. Some pesticides remain harmful to beneficials for weeks after application in the greenhouse. When a chemical intervention is planned within an IPM programme, its effect on subsequent biological agent releases must be checked before application; skipping that check means losing a significant part of the investment. In our experience, growers who skip the waiting period after a chemical spray lose the beneficials released within the following two to three weeks and have to restart.

What is the economic threshold and how does it drive intervention decisions?

The economic threshold is the pest population density at which crop damage begins to produce a measurable economic loss. This concept is arguably the most important part of IPM: not intervening every time a pest is seen, but identifying the point where intervention is necessary based on data.

For a population that stays below the threshold, the cost of intervention — spray, labour, risk of damaging beneficials — typically exceeds the value of yield protected. Setting the threshold correctly both prevents losses and cuts unnecessary spending. Threshold values vary by crop, pest species and market conditions; published sector guidelines can be used as a reference, but calibrating them against your own greenhouse’s historical data tends to give more reliable results.

In practice this means asking the same question consistently: “What do my card counts and plant observations show? Is the trend rising, stable or falling?” Answering that question weekly or fortnightly gives enough information to make early and accurate decisions. Thresholds cannot be used without trend data; this is why monitoring comes before the threshold concept in the IPM sequence, not after it.

When and how does chemical control enter an IPM programme?

IPM does not exclude chemical control; it moves it to the end of the option list. When monitoring data shows the economic threshold has been crossed and biological or cultural measures alone are not sufficient, a suitable chemical product is applied.

The word “suitable” is critical here. In IPM the criteria for selecting a chemical are: proven effectiveness against the target pest; low toxicity to biological agents currently in the greenhouse or due to be released; a short residue profile; and, where possible, selective rather than broad-spectrum action. Broad-spectrum products can collapse the natural enemy population that the next biological measure depends on, which is why they sit at the bottom of the preference list in IPM.

After a chemical application, continuing biological agent releases without observing the waiting period leads to agent losses. Checking that period from the product label and from reliable compatibility lists is essential to protect the investment. Timing this correctly — applying the chemical, waiting, then resuming releases — requires the kind of calendar discipline that monitoring already builds.

Where does a grower start with IPM in practice?

There is no need to wait for a complete plan before beginning; the best starting point is to start monitoring in the current season. The first step is to set up a monitoring system: hang sticky cards at appropriate positions, count on the same day each week and record the numbers in a notebook or a simple table. That data will show, within a few weeks, both when intervention is warranted and whether interventions are actually working.

The second step is to review cultural measures and close any gaps: a crop debris collection routine, entrance hygiene, tool cleaning. Most of these adjustments require no extra spending; they ask for working habits to be reorganised.

The third step is to research biological control options and choose an agent matched to the pest pressure the monitoring has identified. Before the first release, check that the chosen agent is compatible with the target pest and with the temperature and humidity conditions in the house. To see how all of these components fit together and what tools are available across the silo, the biological control in greenhouses hub is a good place to start.

IPM does not settle into a fully working system within a single season; it takes patience. But patient application turns pest management from a reactive crisis mode into a proactive system. The most common feedback we hear from growers who have made that transition is this: it felt like more work at first, but by the end of the first year everything became far more predictable.