Integrated Pest Management Guide: Thresholds That Pay

Integrated pest management (IPM) is a way to decide when to control a pest, not a list of products. You identify the pest, count it with a set method, compare the count with a published action threshold, and only then pick a control, starting with the least disruptive option. The US EPA lists four steps: set action thresholds, monitor and identify pests, prevent problems, then control.

That order is the whole method, so this guide is built around the numbers inside it. You get the thresholds that extension services and industry bodies in the United States and Canada publish for soybean aphid, lygus bug in cotton and flea beetle in canola, a chart of what each spray costs per acre, and a calculator that shows how much yield loss a single spray has to prevent before it pays. Always follow the product label and your local rules when you spray, and ask a licensed adviser if you are unsure.

What integrated pest management means for a grower

EPA describes IPM as an approach that uses information on pest life cycles and the environment, together with the control methods available, to manage damage by the most economical means and with the least possible hazard to people, property and the environment. The FAO, in its own IPM overview, describes it as a dynamic process that weighs the full range of control options against economic, environmental and social considerations.

IPM is also a scale, not a badge. EPA says that there is no national certification for growers who use IPM, and that food grown with IPM is in most cases not identified in the marketplace. If a buyer or supplier says “IPM certified”, ask which programme issued the label.

The four steps, in EPA’s order, are:

1. Set action thresholds. The threshold is the point at which pest numbers or conditions show that control must be taken. Seeing a pest is not a threshold.
2. Monitor and identify. Count the pest the same way each time, and make sure you are not treating a beneficial insect by mistake.
3. Prevent. Rotate crops, choose resistant varieties and use pest-free planting material.
4. Control. Use targeted tools first, such as pheromones, trapping or mechanical weeding. EPA calls broadcast spraying of non-specific pesticides a last resort.

How IPM defines an action threshold

An action threshold is the point at which pest populations or conditions show that control must be taken. That is the EPA wording. It is the trigger you set before scouting begins, and it is the answer to the common test question about what an action threshold is. It is not the number of control methods you have, not the most pesticide a label allows, and not the gap between scouting visits.

A usable threshold always names three things: the pest, the crop stage and the sampling unit. “Ten aphids” is not a threshold. “250 soybean aphids per plant on most plants, with the population still rising” is one. The next section lists real examples with their sources.

There is a second reason to learn the terms. Three numbers are often mixed up, and the gap between them is money:

• Damage boundary: the lowest pest level at which yield loss can be measured. Spraying below it cannot pay.
• Economic injury level (EIL): the level at which the value of the yield loss equals the cost of control.
• Economic threshold (ET), or action threshold: the lower level at which you act, so the spray lands before the pest reaches the EIL.

Iowa State’s Erin Hodgson explains in a July 2016 article that for soybean aphid the ET sits well before the EIL, and even before the damage boundary. Our companion page on action thresholds and when pest control is truly needed walks through how to apply one in a field.

Published action thresholds you can check

Thresholds change with crop stage and region, so treat these as worked examples, not rules for your farm. Each comes from a public extension or industry page, and each states how to sample.

The lygus threshold slides upward as the crop matures, which shows why a threshold must be read with its date and stage. UC IPM’s cotton guidelines for lygus bug start sweep-net sampling at first square, twice a week, and ask you to read fruit retention alongside the sweep counts. They also warn that late plantings, vigorous cotton and high plant populations lower fruit retention, which pulls the threshold down.

The canola example shows why the trigger sits below the damage level. The Canola Council of Canada says canola seedlings can lose 50% of leaf area without a significant yield penalty, but leaf loss can climb from 25% to 50% in as little as a day in a severe attack. The 25% trigger buys time to get the sprayer out. The Council also notes that these figures were set for earlier plant-population targets and older seed treatments, so thin stands may need a lower trigger.

Chart

Lygus bug threshold rises through the cotton season

bugs per 50 sweeps; ‘more than’ means UC lists a greater-than trigger; mid-squaring is 7 to 10 (7 shown)

Soybean aphid: how the thresholds stack up

Soybean aphid is a well-studied case in the US Midwest. SDSU Extension reports that a 2007 research paper put the economic threshold at 273 aphids per plant (with a seven-day lead time), the economic injury level at 674 and the damage boundary near 485. The field rule of 250 per plant on 80% of plants is kept because it falls inside that range and is easy to remember.

Chart

Soybean aphid: four numbers on one scale

aphids per plant, 2007 research figures as reported by SDSU Extension

The same SDSU page recalculated the EIL and ET with 2016 prices: soybeans at $10.01 per bushel, a 46 bushel yield and a $5.25 per acre application fee. The result changes with the product and rate, but the lower values fall near or below the damage boundary, where yield loss cannot be detected. SDSU’s point is that a lower trigger is not more careful. It removes the natural enemies that hold small aphid populations down and adds selection pressure for resistance. SDSU notes that pyrethroid-resistant soybean aphids have already been found in Minnesota (Koch, 2016).

The sampling matters as much as the number. A count of 250 means very little if it comes from the field edge only, and a single count cannot show whether the population is rising. Record the number, the date and the growth stage every visit.

Chart

Recalculated thresholds by product and rate

aphids per plant, 2016 South Dakota prices ($10.01 per bushel, 46 bu per acre)

▶ Scouting and control strategies for soybean aphid. · 22:28

What a spray costs per acre

The cost side of the sum is often a fixed fee plus a product cost. The chart below shows the 2016 South Dakota figures SDSU used: three active ingredients at two rates, plus the $5.25 per acre application fee. These are old, list-style example prices. Get today’s quote from your supplier and custom applicator before you decide.

Chart

Cost of one insecticide application per acre

US$ per acre including the $5.25 application fee, SDSU 2016 example

This is why a tank-mix “just in case” is a weaker argument than it sounds. Even the cheapest option in SDSU’s table adds up to about $8 an acre with the fee, and it brings the resistance and natural-enemy costs described above.

The five IPM tactics, in the order to try them

“Integrated” means the tactics run together, but they are not interchangeable. The table is our own ordering of common tactics, least disruptive first, in line with EPA’s order of prevention, then targeted tools, then broadcast spraying last.

The order matters more than the list. A broad-spectrum spray in June can remove the natural enemies you were counting on in August, which is how a one-pest problem becomes a two-pest problem. UC IPM’s apple guidance shows the same logic for codling moth: mating disruption is the preferred tool because of its low toxicity to people, natural enemies and the environment, though it may need insecticide sprays on top in the first few years. It also tells growers to rotate mode-of-action groups to slow resistance.

▶ IPM strategies for peach orchards, from spring to summer. · 20:27

Spray break-even calculator

The calculator below answers one narrow question: how much yield would this one spray have to save to pay for itself? Enter your own yield, price and costs.

Try the numbers for your own farm below.

Biopesticides and pheromones

Biopesticides are one way to cut broad-spectrum use without giving up chemical control. EPA defines them as pesticides made from natural materials such as animals, plants, bacteria and certain minerals. Its page on what biopesticides are counts 390 registered biopesticide active ingredients as of 31 August 2020. That list is updated, so check EPA’s current list before quoting a number.

Pheromones are a practical entry point. EPA’s pesticide registration manual, in Chapter 3, says that pheromones labeled for use only in pheromone traps, and traps where they are the sole active ingredient, are not subject to FIFRA regulation. Pheromone-only monitoring traps therefore carry no registration step, which makes them a low-cost way to start counting. EPA notes that pheromones used with conventional pesticides, or applied other than in traps, are still regulated. UC IPM adds that traps set at the same height as pheromone dispensers help fix the biofix date used for degree-day timing in codling moth.

A biopesticide does not remove the need for resistance management. Rotating between two products that share a mode of action is not a rotation. Read the label for the mode-of-action group and the pre-harvest interval, and follow local rules.

IPM at scale: Australian cotton

CSIRO states that its pest management research and cotton varieties with insect-resistance traits helped reduce insecticide use by 85 per cent in the Australian cotton industry, with the trait aimed at Helicoverpa caterpillars. CSIRO credits both its research and GM insect-resistance traits, and notes that other pests (aphids, mirids, whitefly, thrips) have since emerged as the main caterpillar sprays fell. The page, last updated in January 2021, does not give the baseline year, so read the figure as a direction of travel rather than a guarantee for any one farm.

The lesson for growers elsewhere is the discipline behind the number: decisions based on sampling and valid thresholds, selective products when a spray is needed, and natural enemies kept alive. CottonInfo, the Australian cotton extension programme, publishes insect and mite management material online. Whatever source you use, treat thresholds as documents with a revision date.

Satellite monitoring between scouting visits

No satellite can count an aphid, and a sweep net count cannot be taken from orbit. What satellite images can do is show where a crop is changing so you know which part of the field to walk first. For a block of several hundred acres, UC IPM’s lygus advice of sampling twice a week from first square is easier to follow if a vegetation map points you to the weaker areas. Farmonaut Satellite + AI Farm Monitoring System provides crop health indices at field scale for that purpose. The change on the map is a prompt to scout, not a diagnosis of the pest.

Records are the other half. A season of dated counts, spray decisions and re-counts is what lets you spot a product that has stopped working. Teams that want field data in their own software can use the satellite and weather API and its developer documentation. See also Farmonaut for the field monitoring app.

▶ How NDVI maps show crop stress across a large farm before it is visible from the ground. · 4:09

A season-long IPM checklist

1. Before planting: list the three pests that cost you most in the last two seasons. For each, download the threshold page from your own extension service and note its revision date and sampling unit.
2. At planting: use the prevention tactics EPA names: rotate away from the previous host, pick a resistant variety where one exists, and use pest-free planting material.
3. From emergence: scout at the interval the threshold document assumes, not the one that suits your diary.
4. Every count: write down the number, date, growth stage and whether the population is rising or falling.
5. At a threshold breach: run the break-even sum with today’s product and application quote.
6. Choosing a product: pick the most selective option that works, check its mode-of-action group against last season, and confirm the pre-harvest interval on the label.
7. After spraying: count again after the interval your extension service advises (SDSU speed scouting re-checks at 3 to 4 days). This is the step most often skipped, and it is your only evidence that the product still works on your population.
8. End of season: compare treated and untreated strips. If you cannot see a difference, the trigger may have been set too low.

Related pages on our site: organic pest control and sustainable farming practices, aphids versus mealybugs, large-scale farm management software, carbon footprint tracking, product traceability, fleet management and crop loan and insurance verification.

FAQ

How does IPM define an action threshold?

EPA defines it as the point at which pest populations or environmental conditions show that control must be taken. It is a trigger level set before scouting, not the number of control methods, the maximum pesticide rate or the time between visits.

What are the steps of IPM?

EPA lists four: set action thresholds, monitor and identify pests, prevent problems, and control. The order is deliberate, because the threshold exists before the pest does.

What is a simple example of IPM?

A soybean grower counts aphids on whole plants, compares the count with the 250-per-plant rule used by SDSU Extension and Iowa State University Extension, and sprays only if most plants (80% or more) are infested and numbers are rising. UC IPM gives a tree fruit example: use mating disruption for codling moth, add traps to time sprays, and treat only if counts show disruption is being overrun.

Does IPM mean never using pesticides?

No. EPA says control starts with targeted tools and moves to spraying when monitoring shows less risky options are not working. Broadcast spraying of non-specific pesticides is the last resort. Always follow the label.

Is there an official IPM certification?

EPA states there is no national certification for IPM growers, and that IPM-grown food is in most cases not identified in the marketplace. Ask which programme a label refers to.

Has IPM reduced insecticide use anywhere?

CSIRO reports an 85 per cent fall in insecticide use in Australian cotton, linked to its pest management research and insect-resistant cotton varieties. The baseline year is not stated, and one farm’s result will differ.

The short version

IPM comes down to one number: the count at which you act. Take that number from a dated threshold page for your crop and region, sample the way the page says, run the break-even sum with today’s costs, and count again after every spray. The tactics are the menu you order from once the count says to order something. This guide is general information; follow your local extension advice, the product label and the rules where you farm.