A non-chemical option for alleviating some insect pressure
Story and Photos Courtesy of Bob Westerfield
As an avid vegetable gardener for more than 30 years, I have grown virtually everything that can be planted in winter and summer gardens. Maybe it’s just me, but it seems like things have gotten more complicated when it comes to growing vegetables. I remember only a decade or so ago planting scores of cucumbers, squash, tomatoes, and everything else and harvesting an abundant crop with very few problems throughout the season. Over the last decade or so, it seems like I am continuously battling more disease and insect issues than ever before. It is also evident that, as a state vegetable specialist, my call volume has increased tremendously, especially questions regarding insect problems in the home garden. The other major trend I have seen is that folks in general now prefer, and sometimes demand, locally, and to some extent, naturally, grown produce. With insect pressures higher than ever, it is becoming quite a challenge to both grow and recommend controls to combat these garden pests. One nonchemical option of alleviating some insect pressure is the use of trap crops.
My first experience with trap crops was in my own garden, quite by accident. I always seem to have terrible, pesky pigweed in my garden. While it is a difficult weed to control, it did not take long for me to realize that it is also super attractive to multiple bad bugs that would otherwise be on my vegetable crops. I have seen everything from potato beetles to leaf-footed bugs devouring pigweed. While I am not suggesting you plant pigweed in your garden, it does provide evidence that certain “bad” are attracted to plants other than your prized vegetables.
Trap cropping is not a new concept, but it is not widely used in home gardens. Essentially, a trap crop works as a decoy, or alternative host, that hopefully lures invading insects away from your vegetables. Once the target insects infest the trap crop, they can be sprayed with insecticides, reducing the invading population. The end result is reduced use of pesticides on edible crops, which makes them healthier. In some cases, insects actually prefer the trap crops and will go there first. Trap crops do not work for every type of insect and are fairly specific about what they help control.
There are several ways to implement a trap crop system. To attract damaging insects, plant a separate block of desirable crops about two weeks earlier than the main crop. Grow the trap crop a short distance away, approximately 8-12 feet.
Cherry tomatoes are one example of an effective trap crop. Although they may be a desirable crop in the garden, they are highly attractive to insects, including stinkbugs and leaf-footed bugs. A small block of cherry tomatoes planted a distance from the main crop will often attract the majority of pest insects. The trap block can then be sprayed to knock down the invading pests.
Hubbard squash is another effective trap crop, luring in cucumber beetles, squash vine borers, and squash bugs. These large, vining type plants need a lot of room to grow. Because they are a winter squash, they will grow all season and will not be ready to harvest until the fruit is mature at the end of the season.
Okra is highly attractive to leaf-footed bugs and stinkbugs. It is also a highly desirable home garden vegetable. Similar to cherry tomatoes, a sacrificial block of okra can be planted to draw insects away from the garden. It can then be sprayed with chemicals once the invading insect’s population is high enough.
Another form of trap cropping is to use an entirely different species of plant. In many cases, the trap crop will be completely unrelated to the vegetable you are trying to protect, but will attract the same type of pests. Sorghum and sunflowers (Helianthus spp.) are examples of trap crops that can be used near desirable plants. Research has shown that both of these plants are extremely attractive to stinkbugs and leaf-footed bugs. Both trap crops are extremely inexpensive to establish from seed.
Since the trap crop is most effective when it begins to flower or seed, it is important to establish it earlier than the desirable crop. Ideally, you’ll plant the trap crop two weeks before the desirable crop. To provide extended control, continue to stagger new plantings of the trap crop every two to three weeks. Two to three rows of each trap crop should be planted at a time. It is important to scout trap crops frequently to prevent the insect population from getting out of hand before some type of control measure is applied. Trap crops will need care similar to your desired crops when it comes to fertility and irrigation. Weed infestation should also be managed with mechanical or chemical methods.
Trap cropping is one weapon that can be used to combat insect pressure for the home gardener. Research has shown that it can assist in providing some relief of insect pressure to desirable crops. Trap cropping may not work for everyone, but it is a possible solution for those who want to use fewer chemicals in their garden.