Edible Produce·6 min read

Trap Crops: Using Sacrificial Plants to Lure Pests Away

Nasturtiums with orange flowers growing densely in a garden bed
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The short version: A trap crop is a plant you grow on purpose to draw a particular pest away from your main crop, so you can deal with the pest where it gathers. It is not the same as companion planting, and it does not protect a bed by itself. Identify the pest first, choose a pairing with evidence for that pest, get the trap growing ahead of the crop, and check both the trap and the crop often. If you do not remove or control the pests on the trap in time, it becomes a breeding site.

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Trap cropping sounds almost too neat: plant something the pest likes more than your crop, let it gather there, and deal with it in one place. It can take pressure off a crop, but it is closer to a small experiment you manage than a plant you sow and forget.

It also gets muddled with companion planting, so it is worth being clear about what a trap crop is before you rely on one.

What a trap crop is, and is not

A trap crop is a plant grown specifically to attract and hold a pest, drawing it away from the main crop so the pest can then be removed or controlled on the trap. It is a decoy.

That is different from companion planting, which aims for mutual benefit, such as masking a crop or feeding beneficial insects. It is also different from insectary or nectar plants, which are grown to feed and shelter the predators and parasitoids that eat pests. In short, a trap crop pulls the pest in, while an insectary plant pulls the pest's enemies in.

How to use a trap crop

How to manage a trap crop in four steps, and what happens when you do not: managed, the pest gathers on the trap plants and is binned; unmanaged, it breeds on the trap and spreads to the crop
  • Identify the pest first. A trap crop works for a particular pest, not for pests in general. Different insects share common names in different countries, so check what you actually have before choosing a trap.
  • Plant it early. Sow the trap earlier than the main crop, or around its edge, so it is larger and more attractive when the pest arrives. Where the trap sits relative to the crop can change how well it works, so be prepared to try a different position next season.
  • Check the trap and the crop. Look at both at least weekly while the pest is active. A trap can draw pests in from outside the garden as well as holding the ones already there, so the crop needs watching too.
  • Deal with the pests before they spread. Once the pest has gathered, squash or hose off small numbers, or pull the trap plants, seal them in a bag and put them in the rubbish bin. Do this before the pests breed up and move on.

An unmanaged trap simply becomes a nursery, breeding up the very pest you wanted to remove. This is the most common way trap cropping backfires.

Pairings to try, and how sure we can be

Aphids crowding the underside of a nasturtium leaf

Some pairings have research behind them, and others are traditional garden practice that may or may not work in your patch.

  • Winter cress and land cress for diamondback moth. Diamondback moths lay eggs on winter cress, also called yellow rocket (Barbarea vulgaris), and on land cress (Barbarea verna), and in a laboratory study the caterpillars did not survive on land cress or on most types of winter cress tested. A couple of the winter cress types did let caterpillars survive, so not every plant sold under these names will behave the same way. Results in the field have been mixed, including a trial in the United States where winter cress did not reduce moth damage to broccoli. There is no good evidence that it works for cabbage white butterfly.
  • Nasturtium for aphids is a traditional home-garden choice rather than a researched one. Aphids, especially black aphids, often cluster on nasturtiums, which makes them easy to spot and remove, but there is little evidence that nasturtiums protect a nearby crop on their own.

You may also read that mustard is a trap crop for harlequin bugs. That research was on a North American bug. The Australian harlequin bug is a different insect whose host plants include weeds such as mallow and dock, and NSW advice is to manage it mainly by controlling those weeds.

Marigolds are often listed as trap crops too, but that is a different job. According to the University of Florida, some marigold species and varieties can reduce root-knot nematode numbers when grown densely, as a cover crop, for at least two months before the vegetables go in on the same spot. Planting a few marigolds among vegetables did not reduce nematodes. Results depend on the marigold and the nematode species, so do not expect any marigold to protect a bed, and do not treat marigold as an insect trap. Our guide to root-knot nematode covers other ways to manage it.

Being realistic about trap cropping

Orange and yellow nasturtiums planted along the edge of a raised bed of brassicas

Trap cropping is variable in a home garden, with results that range from useful to negligible depending on the pest, the timing, the spacing and how attractive the trap is. It works best as one part of a wider approach, alongside netting, good garden hygiene, crop rotation, encouraging beneficial insects and hand removal. And it needs active management, because a trap you never deal with can make things worse rather than better.

Trap crops across Australia's climate zones

The idea is the same everywhere. What changes is when the pests arrive, so time the trap to be growing well before your main pest season. These zones are broad groupings, so if your garden sits between two, go by your local conditions.

  • Tropical (far north Queensland, the Northern Territory Top End, the Kimberley in Western Australia): pests are active for much of the year, so the gap between sowing a trap and needing it is short.
  • Subtropical (south-east Queensland, the northern New South Wales coast): a long warm season, so stagger trap plantings and keep checking them.
  • Arid and semi-arid (inland New South Wales and Queensland, inland South Australia and Western Australia, central Northern Territory): pests follow the irrigated growing season, so sow traps to match it.
  • Temperate (coastal and southern New South Wales, the ACT, much of Victoria, south-east South Australia): set traps out in spring, ahead of the summer pests.
  • Mediterranean (Perth and south-west Western Australia, Adelaide and southern South Australia): time traps to the spring pest flush before the dry summer.
  • Cool and alpine (Tasmania, alpine and highland Victoria and New South Wales): a shorter season, so sow traps as soon as the soil warms.

Frequently asked questions

What is a trap crop?

A plant grown to lure a particular pest onto itself and away from your main crop, so you can remove or control the pest where it gathers.

How is a trap crop different from a companion plant?

A companion plant is grown to help its neighbour. A trap crop deliberately attracts the pest, and then needs you to deal with it.

Do I have to remove it?

You have to deal with the pests on it. If you leave them, they breed and move to your crop, so remove the pests or the trap plants before that happens.

What is the best trap crop for aphids?

Nasturtium is the traditional choice. Aphids often gather on it, which makes them easy to find and remove, but it will not protect a crop unless you check it and act.

Will a trap crop attract more pests?

It can. A trap may draw pests from outside the garden as well as from your crop, which is why you need to check both regularly and act as soon as pests build up.

Does it really work?

Sometimes well, sometimes not. It is most reliable when the pest is correctly identified, the trap is ahead in growth and well placed, and you actively manage it alongside other methods.

Know your pest, plant the decoy early, watch it and the crop, and act before the pests move on, and a trap crop can take some pressure off the plants you actually want to harvest.

Sources we checked

Written by the Happy Valley Seeds team. Last reviewed on 18 September 2026. We checked the main facts in this guide against these sources:

Related growing guides

Want to try a decoy for aphids? Browse our nasturtium seeds, and plant them where you can check them easily.

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