How Do Sticky Traps Work for Garden Pest Control?

Sticky traps are one of the simplest and most affordable monitoring tools in an IPM programme. They catch flying pest insects on a non-drying adhesive surface, giving you data on which pests are present, how their numbers are changing week by week, and when to take action. Used correctly they also provide some direct control of flying pests, particularly in enclosed spaces.

Understanding what sticky traps can and cannot do — and how to read the information they give you — makes them genuinely useful rather than a passive hope.

Yellow vs. Blue Sticky Traps

Colour matters because different pests are attracted to different wavelengths. Yellow traps attract a very wide range of flying insects including whitefly, aphids, fungus gnats, leaf miners, and thrips adults. They are the general-purpose monitoring tool. Blue traps are more specific to thrips — if thrips are your target pest, blue traps give you cleaner, more interpretable data by catching fewer non-target species. Use yellow traps for general surveillance and blue traps when you know thrips are your problem.

Where and How to Position Traps

Position traps at canopy level — most flying pests move within the crop rather than above it. Hang traps horizontally just above growing tips so insects flying between plants encounter the sticky surface. In a greenhouse, place one trap per 10–15 square metres as a monitoring baseline. Outdoors, traps are most useful in tunnels, under cloches, or near pest-prone crops like brassicas and beets.

Avoid placing traps where they will catch large numbers of beneficial insects — away from nectar flower patches and not in corridors where predatory insects actively hunt.

Reading Trap Catches

Count catches twice a week and record the number. You are looking for trends — a sudden doubling in whitefly catches over two days signals a population surge that warrants intervention. A stable catch with low numbers and visible natural enemies on the crop suggests the ecosystem is managing the situation. Replace traps when more than 50% of the surface is covered, as efficacy drops significantly when coverage is high.

Direct Control vs. Monitoring

In a small greenhouse or polytunnel with a modest flying pest population, sticky traps can make a meaningful direct contribution to pest reduction by catching adult insects before they lay eggs. Outdoors with normal air movement, this direct control effect is minimal — their value is almost entirely as monitoring tools. Do not rely on traps alone as a control measure in large or outdoor growing spaces.

Protecting Beneficial Insects

Sticky traps are non-selective and will catch beneficial insects including parasitic wasps and hoverflies. Position them carefully to minimise this, and consider removing or covering traps briefly if you have recently deployed beneficial insects nearby.