Trap Cropping to Control Pests

, written by Jeremy Dore gb flag

Sorrel being grown next to lettuce and beans as a trap crop to keep slugs off

Most gardeners have experienced the disappointment of carefully raising a vegetable crop only to have it damaged or destroyed by an invasion of pests such as slugs, aphids or other bugs. The traditional advice in such situations is to heavily spray crops with pesticides but many of us prefer to use nature's own organic controls for the food we are going to eat. Trap cropping is one of those valuable organic techniques and is regularly used by organic farmers yet few gardeners are aware of the benefits it offers.

A trap crop, also known as a sacrificial crop, is a plant that you add to your garden to attract pests away from the main crops you are growing. The reasoning is this: just as many children will choose ice-cream over a plate of vegetables, likewise most garden pests have preferences for what they like to live on. By planting rows of a trap crop (the 'ice-cream') near to your vegetables the pests will be attracted to the trap crop and will usually leave your main crops alone. You don't harvest anything from your trap crop ñ it is just there to keep the pests off the plants you want to do well.

There are several factors which need to be taken into consideration when planting a trap crop:

  • Different insects prefer different trap crops: Which trap crop you choose depends on the pests you are trying to trap. If the plant isn't sufficiently attractive to the pest then it won't be any use so it is vital to pick the right ones. Often this is a matter for experimentation coupled with observation of what the pests go for in your garden.
  • Layout of the trap crop: For some insects it is sufficient to plant the trap crop around the border of your growing area. Others are harder to stop and it may be necessary to interplant them to draw them off the main crops. Quantities will depend on the insect you are trying to deter but farmers usually set aside something in the region of 20% of the main crop area for the trap crop. Smaller gardens growing a variety of vegetables will often need less than this.
  • Timing: Most insect invasions happen at a specific time of year. For example, I almost always get an aphid invasion in late May or early June. It is important to have the trap crop already well established by the time pests arrive.
  • Beneficial Insects: Trap crops are just one part of good organic pest control and need to be balanced with adequate companion planting of flowers to attract beneficial insects such as lacewings and ladybugs which feed on the pests.

A common concern with trap crops is that they could just act as breeding grounds for the pest which will then move on to the main crops. This can happen but several factors usually prevent things getting out of hand:

  • When pests increase so do their predators. The pests may be building up on the trap crop but as long as you have built in some companion plants there will usually be a hungry population of beneficial insects to start eating them. Often this controls the pests sufficiently and no further action is necessary.
  • When a trap crop becomes overrun with a pest you can remove it or thin it out. The pests are then disposed of with the plant on the compost heap or somewhere further away from the garden.
  • Alternatively choosing a trap crop with a long growing season or making more than one sowing of the trap crop can keep the pests at bay until the main harvest is complete.

Examples of Trap Crops

So, what plants are available to act as trap crops for the various pests that affect vegetable gardens?

Nasturtium
Nasturtium makes an excellent trap-crop to keep blackfly off other crops
  • Nasturtiums are very attractive to aphids (blackfly, greenfly, whitefly) which will often completely cover the stems. Expect to see ants 'farming' the aphids for the honeydew they release.
  • Nettles also attract aphids and because they do this early on in the season they are often followed by beneficial insects such as ladybugs.
  • Chervil is said to be very attractive to slugs.
  • French Marigold is variously reported to attract slugs, thrips and nematodes.
  • Radish is said to attract flea beetle and root fly away from cabbages although various other brassicas can be used as trap crops too so it is best to experiment with Chinese cabbage and collards as well.
Nettle
Nettles attract aphids which are followed by ladybirds

There is an excellent summary of the various trap crop combinations supported by research together with the pests they control on the German-based Pesticide Action Network website (in English).

Do they Work?

My own introduction to trap crops was rather accidental as I observed pests being attracted to other plants in my garden. Last year I grew sorrel with my lettuce and was surprised to see many slugs and snails living in its shade. As sorrel is such a fast-growing plant which retains moisture in its dense stems and leaves it was perfect for slugs and they didn't bother with my lettuce seedlings at all. So, this year, I deliberately retained the sorrel to keep the slugs at bay.

In other years I have grown nasturtiums which are great for keeping blackfly off beans and whitefly away from lettuce and currant bushes.

My experience so far is that trap crops are very useful but it is important to remember that they are just part of the equation. Also effective are methods that confuse flying pests (which will usually jump about amongst plants when first landing on a garden). A mixture of plants makes it far less likely that they will settle on the main crop and should be part of any companion planting strategy.

So, comprehensive organic pest control involves:

  • Diverse planting to confuse pests
  • Including flowers to attract beneficial insects
  • A few trap crops targeted at pests you know you have in your garden
  • Crop rotation to avoid pests overwintering in the soil (see our Crop Rotation article)

...and plenty of experimentation!

If you know of any particularly good crops for keeping pests away then please do add them below as a comment...

Pests, Beneficial Insects and Plant Diseases

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If you've seen any pests or beneficial insects in your garden in the past few days please report them to The Big Bug Hunt and help create a warning system to alert you when bugs are heading your way.

If you need help designing your vegetable garden, try our Vegetable Garden Planner (for PC & Mac) or if you'd prefer an app for your mobile or tablet device, our iPad & iPhone app Garden Plan Pro is available on the App Store here.

Show Comments



Comments

 
"Purple Majesty millet as trap for squash bugs. Two years ago I grew Purple Majesty Millet for its ornamental appeal. I was surprised to find it absolutely covered with squash bugs throughout the whole season. I was able to cut off the grain heads covered with young squash bugs and burn them. I also dusted the grain heads with flour to suffocate the young squash bugs. It certainly attracted them away from my squash. The next year my timing was not good and the squash was already established before the millet matured. I'm trying it again this year. Hope it works again. I live in north Texas."
Jackie on Friday 4 June 2010
"Thanks for adding that Jackie. We often get people asking about what they can do to prevent squash bugs so please do post back and let us know if the purple majesty millet does the job again this year."
Jeremy Dore on Friday 4 June 2010
"Thank you so much for your comments on deterring the squash bugs. I never had any for years of gardening. Then three years ago, they invaded. I haven't been very successful in getting rid of them. I hope the Purple Majesty Millet will help (if I can find some). I always plant Marigolds in my garden to deter bugs. It works pretty good, but not on Squash bugs! Thanks again."
Dianne on Friday 4 June 2010
"I heard that planting onions with squash will deter squash bugs, so I am trying that this year. I also heard that diluted onion juice deters them too. JANNINE from giantveggiegardener.com "
Jannine Cabossel on Saturday 5 June 2010
"Hey! Thanks for the onion idea! I'll try it, too. Maybe if I surround my squash plants with marigolds, nasturtiums, and onions, they will survive?? LOL"
Dianne on Saturday 5 June 2010
"Dianne, Barbara Pleasant describes how to deal with squash bugs in the comments section of her recent article about growing squash: http://www.growveg.com/growblogpost.aspx?id=137 which you may find helpful."
Jeremy Dore on Sunday 6 June 2010
"Thanks! I'll check it out."
Dianne on Monday 7 June 2010
"Thanks for the great article on trap crops. I've got a serious aphid infestation on my zucchini plants at the moment, and I'm trying to get the population down. Usually I grow an assortment of plants in combination, but went with a more conventional set-up this year. It's a good lesson learned. This article also helps explain why many of my nasturtiums didn't do so well, too. Why are aphids attracted to them? Is it the color of the blossoms or the dense structure of the plant? Or both? Also, the farm where I work uses sorghum as a trap crop for their eggplant. The border of the field is planted thickly with it. The idea is that the bugs who like eggplant like sorghum more."
Joan Lambert Bailey on Wednesday 23 June 2010
"Sir, this article is very good. it will help me to introduce new idea in my agricultural project i.e. on organic farming. If you are discuss on improve package of practice and crop management I am very oblized to you. have you any journals or books? I want to buy it. thank and regards from Pabitra Paramanya, M.sc. in Agriculture (calcutta university), India."
Pabitra Paramanya on Thursday 5 August 2010
"Hi Pabitra, I'm sorry but we don't have journals or books - we are an online Gardening website not a publisher. However, there are some very good internet sources of research articles on these subjects which can be located using Google."
Jeremy Dore on Thursday 5 August 2010
"I'm in south Louisiana, artichokes work great for luring leaf footed bugs, let the last ones bloom, they stay on them for a couple months. I'll try tha purple majesty, sounds like a cool plant anyway. "
Urban Farmer on Tuesday 28 September 2010
"Marigolds were seriously attractive food for my overabundance of earwigs in a damp cool summer, definitely cut down damage to my swiss chard and spinach."
S. Ontario Gardener on Tuesday 10 May 2011
"Hi Jeremy, you might look up www.jerrybaker.com to start your library of helps. He provides many different books pertaining to organic ways of dealing with pests. The spray I'm using right now seems to be working on the white fly and aphids. He uses garlic, onion, jalapeno pepper, Murphy oil soap, vegetable oil, and warm water. I have been spraying my plants twice a week and it seems to be doing the trick. He has lots of different "Fixers, Mixers, and Elixirs" (his words). Blessings - Faith"
Faith on Thursday 2 June 2011
"My squash, zuch, and cucumbers have always started out beautifully, but become infested with and decimated by squash bugs by late May or early June. This year, I'm trying floating row cover to keep them off, and planting Blue Hubbard Squash as a trap crop ((recommended by High Mowing Organic Seeds)."
Steve from NC on Saturday 31 March 2012
"I love trap cropping with sunflowers.... well I love sunflowers, so why not?"
Miss Lady Bug on Monday 4 June 2012
"Mix some cayenne and garlic in your mixture as well for squash beetles "
Buddyfolks on Thursday 14 June 2012
"thank u"
rajesh khanna on Tuesday 24 July 2012
"I happened to meet a person who was unusual in that he was a part time rice farmer who was working on how to do with less insecticide on his fields. He was spraying the rice plants around the borders of his rice fields and not spraying the rest. That he found was enough to protect the rest of his crop. Didn't realise it then but it sounds like the way trap crops also work, by discouraging the rice hoppers from breeding where they first invaded the field."
Debashis Ray on Sunday 2 September 2012
"Hi Jeremy, Being as we are talking about bugs here's a new one to try. Cut up some slices of cucumber and place on a foil tin with holes in it. The holes allow water to drain out and away from the cucs. The chemical reaction between the cucs and the foil drive the insects away. I placed about 4 of these tins around in my small 24 X36 garden. It's amazing. Cut my slug problem down about 90%. I didn't seem to have any other noticeable problems with bugs this summer. I really had a victory garden this year with 10' tall corn and unexpected 5' tomatoes that my support system couldn't hold. I'll be more prepared next year. I have learner so much from your site I just want to say thank you for it."
Faith K on Sunday 2 September 2012
"I used Murphy's oil soap with chives (I have tons of them) they don't seem to like it!"
shela on Friday 7 June 2013
"If you plant what pests like are you essentially helping those pests? I am missing the "trap" part. It would seem like you are simply providing more of what the pests like, what's preventing them from multiplying and then attacking your crops?"
Pavel on Friday 7 June 2013
"To be really successful, you must take time to understand the pests you are dealing with. What is their life style, how do they invade the garden and how mobile are they (eg crawl, fly, wind blown). Also, understanding growing degree days and how they impact plant and insect growth is important. With some plants you can time planting to miss the most destructive period in a pests life cycle. If you don't want to educate yourself, perimeter trap planting is generally the most effective method. You plant the same plant you are protecting around the edge of the crop area. These plants are almost always attacked first (unless the insects are high flyers). The guard plants can then be sprayed. I know, spray is a dirty word, but if you do not, you will need a very wide perimeter of guard plants and that is very costly and consumes potential crop space."
JC Schneider on Friday 7 June 2013
"To be really successful, you must take time to understand the pests you are dealing with. What is their life style, how do they invade the garden and how mobile are they (eg crawl, fly, wind blown). Also, understanding growing degree days and how they impact plant and insect growth is important. With some plants you can time planting to miss the most destructive period in a pests life cycle. If you don't want to educate yourself, perimeter trap planting is generally the most effective method. You plant the same plant you are protecting around the edge of the crop area. These plants are almost always attacked first (unless the insects are high flyers). The guard plants can then be sprayed. I know, spray is a dirty word, but if you do not, you will need a very wide perimeter of guard plants and that is very costly and consumes potential crop space."
ghidey birhane on Tuesday 12 November 2013
"I do want to share my experience with slugs and ants. I use Dried Molasses each year on my gardens. I throw it around. I have no ants nor do I have any slugs. One treatment will not do the job, but maybe 2 or 3 treatments in the beginning. I was taught this in a gardening class. Dried Molasses is Wonderful for the garden - read up on it."
Carol on Saturday 14 February 2015
"Your comments on trap planting attracted my attention but I'm confused. In the U. S. we plant borage to repel tomato worms; marigolds to deter bean beetles, aphids, potato bugs, squash bugs, nematodes, and maggots; nasturtiums to repel aphids, potato bugs, squash bugs, and to destroy white flies in a greenhouse; and rosemary to repel bean beetles, cabbage moths, and carrot flies. Are our climates that different?"
MaryLena Anderegg on Tuesday 10 March 2015
"Hi Jeremy this is my first visit here and am relatively new to vege gardening. I love your post and am learning heaps thank you very much. What does one do to keep white butterfly away from cabbage, broccoli, cauliflower and brusselsprouts?"
Diane Hoskin on Tuesday 31 March 2015
"My mother taught me to use the following spray for aphids on roses and I will be using it on squash this year. It was successful several years ago when I used it on squash plants. To a gallon of water, add a couple of tablespoons of liquid dishwasher detergent and a small can of snuff. Shake it up and spray leaves and stems. Do not spray the blooms or the squash."
MaryLena Anderegg on Tuesday 31 March 2015
"Along with fruits and veggies I also grow medicinal marijuana and the last couple of years have had problems with green caterpillars. Any suggestions on what I could use to trap crop these caterpillars."
Trent on Thursday 9 April 2015
"Land cress is more attractive to the white cabbage butterfly than your cabbage, kale and broccoli "
Shayne on Friday 10 April 2015
"Hi there, here's what I spray my plants with to get rid of many bugs. Fill up a bucket with tomato leaves and water, let it rest for a few days with no lid on the bucket. Filter and splay directly on the plants with the bugs. You can also use whole tomato plants and experiment simmering them in hot/boiling water. Nasturtium leaves are also ok to add to the mix."
marco on Tuesday 14 July 2015

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