Attracting Beneficials
Answered by: Conrad Richter
Question from: Deborah
Posted on: February 06, 2013

The last pecan production meeting I attended sponsored by our county agent mostly dealt with chemical fertilizer and chemical pest and disease control. I asked about organic solutions to these challenges and was told that red clover attracted beneficials. I didn’t get much else in the was of fertilizer or any other ideas to help thwart off disease and pests. I am hoping you can help recommend some things for me. I feel like this is the time to act.

This touches on the practice of companion planting and the long held belief that certain plants can reduce pests and promote soil fertility. There is no doubt in my mind that certain plants do have the power to enhance growth of garden plants in these ways. But the effects are subtle, perhaps too subtle to meet the expectations of gardeners. If the idea is to eliminate a pest problem or to remove the need for supplementary plant food then companion plants will likely disappoint. If the idea is instead to shift the balance of a complex ecosystem of soil, plants, pests and diseases in one’s favour, then yes companion plants have the potential to do that. But it is never as simple as planting ‘this’ many companion plants to reduce pests by ‘that’ amount.

Just consider the idea of attracting beneficials. If the beneficials in mind are the bugs that go after a pest that is bothering your pecan trees, then the companion plants must first attract the pests. If the hoped for beneficials do not show up to eat all those pests then the pest problem on your trees could become worse, not better. Often it is a crap shoot as to what the outcome will be. And studies to "prove" companion planting have been hampered by this and other difficulties.

But that’s not to say that there is no merit to companion planting, or that there is no point in trying. In fact some of old farming practices have come back in favour, practices that are really rooted in the companion planting philosophy. For example, a common old tactic is to use trap plants. These are plants that pests prefer to attack, thus diverting the pests’ attention away from the plants one is trying to protect. When these plants become infested they are destroyed before pests can spread. This idea does work: for example alfalfa is planted in cotton crops to trap lygus bugs. Wikipedia has a page on trap crops that lists practical examples of trap crops.

There are other proven companion planting tactics, and you may be able to adapt these methods to pecan farming. We know, for example, that certain marigolds can reduce nematodes in the soil and reduce above ground pests. A oft repeated claim is that stinging nettle helps to improve soil fertility of neighbouring plants. But even in this last example, one has to take care to avoid the stinging nettle from overtaking the intended beneficiary crop, and one must watch for pests that take up residence on the ample foliage.

Because companion planting interactions depend on external factors that are difficult to control you will find that there is not a lot effort to develop companion planting methods for your crop. You will need to adapt long time companion practices for your crop. Many probably will not work in your situation, or will have only subtle effects that you can’t be sure about. Here is where sharing experiences with other pecan growers is so important.

If I were you I would start with two approaches: 1) learn as much as I can about companion planting and try to winnow them down to what might work for pecans, and 2) talk to pecan growers who have grown them for many years and see if any have developed special companion plant-like tactics. One other thing that I would implement immediately is an effective pest monitoring program. Regardless of how you control your pests, you will get better results when you are monitoring pests on your crop in a consistent and thorough way throughout the growing season.

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