pests; organic; companion planting; crop rotation

Solve pest problems by using your farm ecosystem

Pest insects destroyed an estimated 18% to 26% of annual crop production worldwide in 2011, according to research from the USDA’s Animal Plant Health Inspection Services (APHIS). Most losses (13% to16%) occurred in the field, pre-harvest, and were heaviest in developing countries. That’s us.

Synthetic chemicals have been used for pest control for the past 50 years. But repetitive use of chemicals to control insects, weeds and plant pathogens has generated its own set of problems. Pests have developed chemical resistance, secondary pests occur and there are toxic residues in plants and/or soil.

There may be ecosystem damage, soil health deteriorates and there are risks to human and animal populations. Another unfortunate negative is that monoculture (a single crop continuously planted), increases the presence of insect pests and soil pathogens.

Synthetic chemicals have been used for pest control for the past 50 years.

As the pest populations increase, crop managers crank up their chemical spray programmes, which leads to further resistance and so on. It’s a vicious cycle.

Rotating with a variety of crops, and planting companion crops can help to break these cycles and improve soil health. The plus for small-scale farmers is that they are better positioned than large-scale farmers to make changes to their farming practices and to try out new methods.


The standard cycle for crop rotation is every three to four years, depending on the crop. Cycling crops limits problem insect populations and soil-borne pathogens. Think of it like this – by rotating crops, the (destructive) bugs don’t have time to get comfortable, and follow-on crops can be chosen for their ability to repel pests.


Companion planting uses a mix of plants to keep pests away. For example, if you plant onions into a cabbage field, the smell of onions is enough to put the cabbage pests off. Unattractive as it may be, the marigold is a very useful companion plant as it repels certain soil nematodes.

Companion plants can act in two ways, they repel, or they attract predatory insects that prey on pest insects.

pests; companion planting; barrier crops
There are many examples of planting with barrier crops that can repel pests or create preferred habitat for them. The barrier crop creates a boundary around the primary crop.


Farming is not rocket science but that doesn’t mean it’s a walk in the park. Farming is a career that demands resilience and the ability to think on one’s feet while scanning the horizon. Take your eye off the ball and it will hit you from somewhere out in left field.

Pest control, crop rotation, soil and plant health, macro- and micro-nutrition, the weather, heat units, water-holding capacity are among the myriad of factors engaging and interacting to ensure a good harvest. These are fairly complex issues that need to be understood.

The word sustainable has become a fairly sickening one

Complex does not mean overwhelming – farmers can limit pests and promote sustainable agriculture, using biological agents and natural systems as models. There is a good agronomist somewhere in your area, and the greatest library on earth is a click away. There are also other farmers; never underestimate their knowledge or their willingness to help a brother grower.

The word sustainable has become a fairly sickening one, used as it is with nauseating frequency by every babbling politician; people who generally know little to nothing of what it means to be out there battling the weather, the markets, the government, the cabals and the pest outbreaks.

But, like it or not, one must look at the sensible use of the soil, our major resource, so that farming does not become synonymous with mining.

Indeed, those who mean to farm our continent to supply their own countries with food will not be that concerned about ‘sustainable’. To survive and thrive, Africans must farm properly giving due attention to detail, diligence and excellence and proper husbandry of the soil. .

I don’t hold with the concept of a shortage of capacity in Africa. There are many highly competent, experienced scientists who devote their working lives to solving agricultural problems and Africa has excellent farmers, large-, medium- and small-scale. The age-old problem of inadequate, corrupt governments is nothing new to farmers.

pests; companion planting
Companion planting in vegetable gardens uses plant diversity and differences to keep pests at bay. Fresh produce farmers know that herbs in the field have crop value as well as the ability to keep insects away. Plants like onions and garlic repel pests with their strong smell and the useful marigold repels nematodes.


Imagine your farm, big or small, as an agricultural ecosystem, with you, the farmer as it’s co-driver. In that ecosystem the parts interact to create balance. This is the law of the universe. The agro-ecosystem will respond to pressure.

It doesn’t help to compartmentalise your farm in the belief that what you do in one part will not affect the other parts. So, if you are to take nature as your model, you must keep looking at the whole system rather than at the individual parts.

Fixing a problem by wiping it out will only ever provide short-term relief. If you put a spoke in the wheel, the bicycle falls over – not the wheel. The synthetic chemical intervention will give a quick fix, nothing more.

When antibiotics have been pumped into a patient for an illness, the immune system weakens and that patient is vulnerable to contracting another illness. A further course of antibiotics is prescribed, the immune system goes down again and the cycle of sickness continues.

The same thing happens on the farm. For years farmers have poisoned pests to save their crops; the pesticide or herbicide works for that season, but next year the pest returns better armed. To build the health back into your system, feed the soil, use planting mixes, target pests selectively rather than broadly, and make sure the plants have the nutrients they need so that they are strong enough to withstand some attacks.

Keep looking at the whole system, whether it’s a field or a thousand hectares.

pests; integrated pest management
These salad greens are grown with no pesticide or herbicide inputs. The farmer says plant health plays a big role. He tolerates the insects that arrive in his field. “The losses are insignificant,” he says.


The use of natural enemies to control animal and plant pests has been very successful in many cases, but the trend is towards mass release of pest predators. Again the solution, while far better than non-selective chemical spraying, looks at applying pressure from the outside.

Pheromone trapping is another form of biological control, acting to lure the moth into a trap as it responds to a sex hormone that calls it to mate. The mating urge keeps the pest off the crop.

It may be time to look more carefully at the strengths in the farm ecosystem

The integrated pest management system (IPM) relies on the farmer’s ability to monitor his (or her) crop, and then combines biological and artificial controls after assessment. Synthetic chemicals are used only when absolutely necessary. IPM works well, it reduces pesticide use significantly, and it makes sense to a farmer and it uses a ‘bigger picture’ method.

It may be time to look more carefully at the strengths in the farm ecosystem and use those strengths to keep your fields in a healthy balance.

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