Trap Crops Help Protect Your Favorite Plants from Insect Pests

Tall tomato plants surrounded by zinnia and dill trap crops for insect pest control.
My Garden Life
April 29, 2024
Table of Contents

By Kelly Miller

Trap crops are a way to offer potentially damaging insects an alternative to eating your valuable vegetable plants. For many gardeners, dealing with pests is one of the trickiest parts of keeping plants healthy till harvest. Invaders such as aphids, Japanese beetles, and slugs can wreak havoc. They weaken plants by munching on shoots and leaves and gobble up ripening veggies before gardeners get the chance to pick them.

There are many methods for dealing with pests, such as removing them by hand, introducing beneficial insects like ladybugs, or planting crops with naturally repellent properties, such as garlic.

Another helpful strategy is the use of “trap plants” that protect crops by providing pests with tasty meal alternatives.

What Are Trap Crops?

Trap crops, also known as trap plants or decoy plants, are those added to a garden to lure pests away from nearby crops. This is a form of “companion planting,” i.e. strategically planting different crops nearby one another to enhance the growth of one or both.

A trap plant is different from a repellant plant. Repellant plants, such as garlic or marigolds, are those that harm or irritate pests via odor, taste, or texture, thus driving them away from an area. A trap plant simply redirects a pest’s attention from one plant to another.

Japanese beetles infest a pink zinnia flower making it a good trap crop to protect other plants.

When planting a trap crop, the goal is to provide pests with one of their favorite foods—something that they like even more than the “cash crop” you’re trying to protect.

Trap crops are used in commercial agriculture. For example, farmers in California plant alfalfa between strawberry rows to lure away lygus bugs. The same strategy can be applied to backyard gardens.

The ideal trap plant is inexpensive and easy to grow in the same conditions as the protected crop. For example, four o’clock flowers are commonly used to lure Japanese beetles away from rose plants. Four o’clock flowers are rapid, low-hassle growers that produce plenty of foliage to keep pests busy. And while these flowers are lovely in their own right, they’re not as precious as roses.

Close up of pink and yellow four o'clock plants in full bloom.

What Are the Best Trap Plants for Popular Garden Crops?

The use of trap plants begins with understanding which pests are attacking your garden. Remember, a healthy garden is full of life, including many types of beneficial insects.

Before implementing a pest management plan, make sure that the damage you’ve detected is being caused by pests, and not by other issues such as disease or over/underwatering. Then, capture a pest in the act of attacking your plants and figure out what it is. The iNaturalist app is a helpful tool for making accurate identifications. 

Once you know which pest you’re dealing with, you can decide on a helpful trap crop. The table below presents a few of the most common combinations of garden pests, affected crops, and effective trap crops. 

Target PestCommonly Affected Cash CropsTrap Crops
AphidsMelons, cucumbers, zucchinis, carrots, beans, beets, broccoli, cabbage, bok choy, kale, spinach, rosesNasturtium, Sunflowers
Cucumber beetleCucumbers, zucchinis, melons, squash, eggplants, beansAmaranth, Zinnia, Blue Hubbard Squash
Tomato hornwormTomatoes, eggplants, peppers, potatoesDill
Japanese beetleBerry bushes, roses, treesEvening Primrose, Zinnia, Marigold, Four O’clock
Slugs and snailsLettuce, cabbage, strawberries, flowersChervil, Parsley
Squash bugs and squash vine borerSquash, pumpkinsBlue Hubbard Squash
Leaf minerSpinach, beets, cucumbers, celery, tomatoes, Swiss chard, cucumber, zucchiniLambsquarters, Columbine

How to Use Trap Crops: Timing, Siting, and Pest Removal

Trap cropping works best when a gardener has prior experience with certain pests and can take a proactive approach. If this is your first season dealing with a particular garden pest, take notes about when they appear and which crops they attack. Next year, you’ll be prepared!

When to Plant Trap Crops

Most garden pests cause problems during a certain time of year and attack plants during specific growth phases. For example, tomato hornworms appear in late July and feed on the leaves of ripening tomato plants. Timing is essential for providing pests with alternative food during the period in which they typically cause damage and populations are high.

A bucket of tomato hornworms plucked from plants and ready to be disposed of.

Trap crops should be established before cash crops. The standard recommendation is to plant trap plants two weeks before planting cash crops.

Plant them early enough so that they’re offering plenty of tempting foliage by the time their partner crop is ripening and vulnerable. Or, as a last-minute pest control approach, purchase mature, potted trap plants and place them near your protected crops to address an infestation that’s already in process.

Where to Plant Trap Crops

Perimeter trap cropping involves planting rows of trap plants that entirely enclose a cash crop. This is an effective method but requires devoting a lot of space to decoy plants. Less-intensive approaches include thin rows of trap plants alongside protected crops, or putting a few potted trap plants around the corners of your garden. Trap plants should be 3–8 feet (0.9–2.4 meters) away from the plants they’re protecting. 

Zinnia, sunflower, and dill trap crops surround rows of vegetable plants in a large vegetable garden.

Removing Pests from Trap Crops

Disposing of Large Insect Pests

Once a large number of pests have accumulated on a trap plant, it’s easy to efficiently kill or remove them. Larger pests can be individually pinched or removed.

A hand is plucking a beetle from a potato plant.

Pluck off the insects and drop them in a bucket of soapy water for quick kill and disposal.

Japanese beetles dropped into a bucket of soapy water to kill them.

Disposing of Small Insect Pests

For small insects like aphids, it’s easiest to cut off heavily infested leaves and then destroy them entirely or dispose of them in a sealed container. If a trap plant is thoroughly covered in pests and near the end of its seasonal growth, it may be best to remove the entire plant.

Spraying plants with insecticidal soap is also an effective way to treat smaller insect pests such as aphids, spider mites, and thrips. You can use insecticidal soap on the affected plants without causing harm to your trap plants and it’s safe to use around food crops. However, keep in mind that any insecticidal spray is usually non-selective and you risk destroying beneficial insects in the treated areas as well.

Explore More Companion Planting Benefits for Your Garden

Trap planting for pest control is just one way that certain plant pairs can work together in a garden. Other companion planting benefits include attracting pollinators and boosting soil nutrients. Access our comprehensive Vegetable Garden Companion Plants chart to learn more.

Orange marigolds are planted among leaf lettuce to help repel insect pests.

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