Professional pest technicians almost never start by treating. They start by measuring. Sticky monitor traps are the cheapest diagnostic tool in roach control, and they answer the two questions that decide whether your treatment works: where is the nest, and how big is it. Most homeowners skip this step, bait blindly, and then conclude the product failed when the real problem was placement. If a product you already placed is being ignored, our guide to why roach bait stops working covers the five usual causes and the fix.
This guide explains how to deploy monitors, how to read what they catch, and how to convert three nights of data into a bait plan that targets harbourage instead of guesswork.
What monitors do that bait cannot
A bait station tells you very little. Consumption is hard to judge, and an empty station could mean the colony is dead or that no insect ever walked past it. A sticky monitor is different: it captures a physical, countable record of traffic at a specific point over a specific number of nights. That gives you three pieces of information.
- Location. Which of your candidate zones actually has traffic, and which are clean.
- Density. Whether you are dealing with a handful of insects or a large population, which sets your expectations for how long treatment will take.
- Composition. The ratio of adults to nymphs, which tells you whether the population is actively breeding and, later, whether your treatment is working.
None of that is visible from sightings. People notice roaches where they happen to be standing at night, which is usually not where the nest is.
Choosing and preparing monitors
Any flat glue board designed for insects works. Avoid rodent glue boards, which are far too large, and avoid pheromone lures for the initial survey because they distort the geography of your results by pulling insects across the room. For a baseline map you want to know where traffic naturally is, not where you can attract it.
- Use plain, unbaited glue boards for the first three nights.
- Number every monitor with a marker and write the room and exact position on the back.
- Fold the boards into a tent shape if the design allows. Cockroaches prefer running through an enclosed channel.
- Place them flush against a wall, cabinet edge, or appliance side. Roaches follow edges; a board in the middle of the floor catches almost nothing.
- Keep them dry. Steam and grease kill the adhesive, so keep boards a short distance from the dishwasher vent and the hob.
- Place them out of reach of children and pets, inside cabinet interiors and behind appliances rather than in open walkways.
A twelve-point placement grid
For a standard apartment or a single-floor home, twelve monitors give a usable map. Increase the count in the kitchen if that is where your sightings are.
| # | Location | What a catch here tells you |
|---|---|---|
| 1 | Back corner under the kitchen sink | Plumbing collar or drain entry as a route |
| 2 | Inside the cabinet directly beside the dishwasher | Warm appliance cavity harbourage |
| 3 | Floor gap beside the refrigerator | Compressor and drip pan nesting |
| 4 | Inside the lowest kitchen drawer, at the back | Cabinet carcass harbourage, often the primary nest |
| 5 | Behind the microwave or on the shelf beneath it | Electronics cavity nesting |
| 6 | Pantry floor, back wall | Food source access rather than harbourage |
| 7 | Under the bathroom vanity, next to the pipe | Riser and wet-wall travel |
| 8 | Behind the toilet base | Damp harbourage and drain access |
| 9 | Beside the washing machine or dryer | Warm motor housing harbourage |
| 10 | Water heater or utility cupboard floor | Central warm zone, common building-wide route |
| 11 | Along the wall the kitchen shares with a neighbour | Migration pressure from an adjacent unit |
| 12 | Inside the entryway, near where deliveries are set down | Introduction via cardboard and grocery bags |
If point 11 catches consistently while your interior points stay clean, your problem is migration rather than a nest, and the strategy shifts toward a barrier. That situation is covered in preventing migration through shared walls.
How to read the catch
Leave the monitors untouched for three consecutive nights, then check them in daylight and record the count for each numbered board. Interpret the numbers rather than reacting to them.
Density
- Zero to two total across all boards: low-level or introduced activity. Targeted placement at the catching points is usually enough.
- Three to ten: an established localised population. Expect three to five weeks of treatment.
- More than ten, or a single board with five or more: a substantial nest very close to that board. Treat that zone as the centre of the problem.
- Adults caught in daylight hours: the harbourage is overcrowded, which correlates with a heavier population than the count alone suggests.
Composition
Mostly nymphs with few adults indicates an actively breeding nest nearby, because nymphs do not travel far from where they hatched. Mostly large adults with no nymphs, especially on perimeter boards, suggests insects arriving from outside your unit rather than breeding inside it. Learning to tell the two apart is worth the effort; our guide to identifying nymphs covers the visual differences.
Direction
Compare adjacent boards. If board 3 beside the refrigerator catches eight and board 6 in the pantry catches one, the nest is at the appliance and the pantry is simply a feeding trip. Traffic decreases with distance from harbourage, so the highest count is your best estimate of the nest location.
Turning the map into a bait plan
- Rank your boards by count. The top two or three define your priority zones.
- Concentrate placements within roughly half a metre of the highest-catching boards, inside the enclosed spaces those boards sit against: cabinet carcasses, appliance cavities, plumbing collars.
- Use several small placements per zone rather than one large one. Cockroaches consume tiny amounts, and coverage beats volume.
- Place a smaller number of maintenance placements at the perimeter points that caught nothing, to intercept future arrivals.
- Do not spray anywhere near your placements. Residual repellents make insects avoid the exact spot you need them to visit, an effect described in why sprays make roaches scatter.
Using monitors to prove the treatment worked
This is where monitors earn their keep a second time. Replace the boards with fresh ones after you bait and check them weekly. You are looking for a trend, not a single number.
- Week 1: counts often rise slightly as foraging increases. Expected.
- Week 2: counts should fall clearly. If they are flat, your placement is wrong, not your product.
- Week 3 to 4: a rise in small nymphs with adults near zero means egg cases laid before treatment are hatching into live bait. This is success, not failure. See cockroach egg cases.
- Week 5 onward: two consecutive weeks of zero catch on every board is a defensible definition of elimination, far more reliable than not having seen one lately.
Mistakes that ruin the data
- Moving boards between checks, which makes the counts meaningless.
- Placing boards in the middle of the floor instead of along edges.
- Using pheromone-lured monitors for the baseline survey and drawing a false map.
- Checking after a single night. Traffic varies; three nights smooths it out.
- Deep cleaning during the survey, which changes behaviour and invalidates the baseline.
- Treating a zero-catch result as proof of elimination in week one. Early zeros usually mean the boards are in the wrong places.
Frequently asked questions
Do sticky traps get rid of roaches?
No, and they are not meant to. Glue boards capture a small fraction of the population and have essentially no effect on colony size. Their value is diagnostic: they tell you where to put the bait that does the actual work.
How many monitors do I need?
Twelve is a good baseline for an apartment or single-floor home. Concentrate extras in the room with the most sightings rather than spreading them into rooms with no evidence at all.
How long should I leave them down?
Three nights for the baseline survey, then swap in fresh boards weekly through treatment. Replace any board that has collected dust, grease, or moisture, since the adhesive stops working.
Should I use bait on the sticky trap?
Not during the survey, because it distorts your map. And never place bait on a glue board during treatment, since you want insects to reach the bait and return to the harbourage, not to be stuck at the station.
Measure first, then treat
Three nights of monitoring costs almost nothing and routinely cuts weeks off a treatment, because it replaces guesswork about where the nest is with a numbered list ranked by traffic. It also gives you an objective way to prove the problem is gone rather than hoping it is.
Once your map identifies the harbourage zones, GreenLeaf RoachBuster gives you 50 odorless, stainless dry powder sachets per box, enough to run several small placements in every priority zone and keep maintenance placements at the perimeter. Always use as directed on the label, and keep both monitors and placements away from children and pets.
Wider reading: the complete Roach Control Guide maps every article on the site by the question you are trying to answer — first 48 hours, identification, method, room by room, comparisons, safety, rentals and local conditions.
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Use only as directed on the product label. Keep away from children and pets.
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