Trap Crops: what are they and how can they help control pests?

By Carrie Falotico, Master Gardener Trainee

Crucifer flea beetles (Phyllotreta cruciferae) and Brassica juncea, a trap crop that attracts these pests.

Plant pests can certainly be one of the most frustrating parts of growing your own food garden. Trap crops are part of an Integrated Pest Management plan. Here’s how they work. 

A TRAP CROP can be defined as a sacrificial plant that draws away damaging insects from the desirable crop.

Essentially, a trap crop works as an alternative host that draws away invading insects, giving the main vegetable crop an added layer of protection. In some cases, insects have a preference for these alternative hosts, and when given the choice, will go to the trap crop first.  After trap crops are infested with target insects, they can be controlled with timely insecticidal applications or mechanical removal. While trap cropping can be extremely beneficial, it is often not a complete solution. Trap crops will not control all insects and the use of integrated pest management (IPM) is necessary. IPM practices include rotating crops, attracting beneficial insects, and prudently using organic and synthetic chemicals.

This article gives a great explanation of trap cropping for small commercial growers. Many of these practices are also very useful in the home garden and can be done on a smaller scale.

Another great resource that details trap crops as well as intercropping and companion planting, that, when combined with trap crops, can make an even bigger impact when controlling pests.

Identification is key

You will definitely want to make sure you have correctly identified the pests causing damage to your plants. Different pests may prefer different trap crops and may require different integrative pest management (IPM) techniques. This resource is a helpful guide to identifying common pests as well as insects that are beneficial and helpful to gardeners.

Example: Flea beetles 

Flea beetles (including Epitrix spp. and Phyllotreta cruciferae) are a well-known garden pest on crops like kale and broccoli. For flea beetle control, Chinese southern giant mustard (Brassica juncea var. crispifolia) is an example of a trap crop that has been used effectively in the United States to protect crucifer crops from flea beetle damage. In studies conducted at Washington State University (WSU), a diverse trap crop containing Pacific Gold mustard (B. juncea), Dwarf Essex rape (B. napus), and pac choi (B. campestris L. var. chinensis) successfully protected broccoli from the flea beetle. Diverse trap crop plantings combine plants that have different phenologies (life cycles which can be influenced by the environment, weather conditions, and nutrition), chemical profiles, and physical structures that make them more attractive to flea beetles. 

It is important to note, however, that trap crops may not provide complete protection, especially during heavy pest infestations. You also have to manage the pests on the trap crop by removing them by hand and killing them, or using insecticide. Trap crops will be even more effective if several integrated pest management strategies are used together, like 

  • Control weeds in and around planting sites to limit food sources for flea beetles.
  • Remove old crop debris so that beetles will not be able to get protection in the winter.
  • Plant crops as late as possible. Plants grow faster in warmer temperatures and are more stable to resist damage from flea beetles.
  • Use row covers or other screening to keep beetles out when the seedlings are growing.
  • Remove row covers before the flowers come up so pollinating insects can reach the plants.

These articles give excellent detail on managing flea beetles:

Explore more

If you are interested in reading more about Integrated Pest Management and how it can help your garden thrive, this is a great resource

I hope you find this information helpful and that these methods help you have a more enjoyable gardening experience!

Before Reaching for Pesticides, Get to Know Beneficials – The Good Guys!

By Judi Di Bord, Master Gardener Volunteer

Did you know there is an alternative to controlling pests in your garden by using a pesticide?  Attracting beneficial insects, like lady beetles, green lacewings, praying mantis and dragonflies can help control insects that feed on your plants.  Beneficials don’t just help control pests. Some beneficials are also important pollinators! 

Ladybug (Coccinella septempunctata) on an Common Yarrow's umbel (Achillea millefolium)
Ladybug (Coccinella septempunctata) on an Common Yarrow’s umbel (Achillea millefolium). By Hélène Rival on Wikimedia Commons.

How can you attract beneficials to your garden?  One way is to purchase them at a local garden center and release them into your garden.  You can also attract them to your garden by growing plants to provide an enticing habitat for them.  If you are able to dedicate some space to growing these habitat plants, the rest of your garden can reap the rewards.

Following are some recommendations from the Penn State Extension Service:

  • Carrot Family (Apiaceae)  Plants in the carrot family are especially attractive to small parasitic wasps and flies. Interplant them in your vegetable garden and flower beds. Plants in this family include: caraway (Carum carvi); coriander/cilantro (Coriandrum sativum); dill (Anethum graveolens); fennel (Foeniculum vulgare); Bishop’s flower (Ammi majus); Queen Anne’s Lace (Daucus carota); and toothpick ammi (Ammi visnaga).
  • Aster Family (Asteraceae)  Attractive to larger predators such as lady beetles and soldier beetles. Incorporate into the vegetable garden and flower beds. Plants in this family include: blanketflower (Gaillardia spp.); coneflower (Echinacea spp.); coreopsis (Coreopsis spp.); cosmos (Cosmos spp.); golden marguerite (Anthemis tinctoria); goldenrod (Solidago spp.); signet marigold (Tagetes tenuifolia); sunflower (Helianthus spp.); tansy (Tanacetum vulgare); and yarrow (Achillea spp.).
  • Legumes (Fabaceae)  Generally grown as cover crops and attractive to many beneficials. Plants in this family include: alfalfa (Medicago sativa); fava bean (Vicia fava); hairy vetch (Vicia villosa); and sweet clover (Melilotus spp.).
  • Mustard Family (Brassicaceae)  Attractive to beneficials that are parasites and predators of the insect pests of the mustard family (broccoli, Brussels sprouts, cabbage, cauliflower, kohlrabi, mustard greens). Be sure to plant these away from the garden rather than in the garden since these plants attract pests as well as beneficials. Some are common weeds, such as yellow rocket and wild mustard. Plants in this family include: basket-of-gold alyssum (Aurinia saxatilis); mustards (Brassica spp.); sweet alyssum (Lobularia maritima); yellow rocket (Barbarea vulgaris); and wild mustard (Brassica kaber).
  • Verbena Family (Verbenaceae)  Attractive to a variety of beneficial insects. Many plants in this family are favorite garden flowers. They include: lantana (Lantana camera); Buenos Aires verbena (Verbena bonariensis); hybrid verbena (Verbena x hybrida); and lilac vervain (Verbena rigida).

Beneficial insects also need a source of water. Shallow containers such as ceramic pot saucers with pebbles for the beneficials to rest on are best.

Suggested OSU Extension publications:

PNW550: Encouraging Beneficials in Your Garden

For kids:

EC1601: The Wildlife Garden: Dragonfly

EC1604: The Wildlife Garden: Lady Beetle

EC1605: The Wildlife Garden: Praying Mantis

Suggested websites:

National Pesticide Information Center, Beneficial Insects.

Penn State Extension, Attracting Beneficial Insects