by Amber

Control Garden Pests with Plants?

Last week, I came across an article about scientists discovering that farmers could reduce pesticide use simply by changing the way they plant a monocrop. Interesting. Can we control garden pests with plants using this concept too? It seems doubtful many farms would implement such a change, unless plagued with pesticide tolerant superbugs. Most rely on those one-shot miracle solutions in a jug. It seems to me that this might just be applicable to backyard garden and urban farm crops. Definitely worth considering, if not trying out. Whether you’re an organic gardener or not.

Row Cropping: Wrong control garden pests with plants approach.

Rows of different varieties looks so neat, tidy, and organized. But is it the wrong approach if we can control garden pests with plants planted differently? (Ridge View)

Just because your ‘field’ is only 20 foot by 20 foot, or a quarter of an acre micro farm, the way we plant crops isn’t that much different than a traditional farm. It’s a matter of scale. They’re still grown in masses, though gardeners are far more into crop diversity than most farms today. A garden has to produce as many different types of foods as we can pack in there. But, we still grow in rows of just one variety of plant – a single genotype. According to the findings of a new study, this is aiding and abetting the enemy. Makes perfect sense – instead of a small source of food, we’ve laid out a feast.

The idea that farmers and scientists don’t quite understand why a field with a variety of plants attracts less pests than one with all the same kind is chuckle-worthy. Forty acres jam-packed with a delicacy is a huge drawing card. Life is good in that bughood! But remember those seeds whose catalog description include “pest resistant” in its attributes. Why is one more prone to insect damages than another?

They think it has to do with nutritional balance. Whatever the insect is getting out of the plants is available in different amounts from one variety to the next. Some might be too rich, while others are low in something vital, and in between there’s perfect. Interspersed planting changes everything. They say it can actually harm the pests. The same kind of approach is used to control disease in rice and wheat. But no one has done this yet as a method of pest control, though the study published in Nature a couple of weeks ago finds that it holds promise.

Digging for more info, since the study is paid access only, I found some quotes from a lead author, William Wetzel, from Michigan State University in a Take Part article:

“What we found was that all these insects have a very specific nutrient level on which they thrive, grow fast, and have high survival… When they get the wrong level of nutrients, they do very poorly.”

“A key result from our study was that the negative of eating plants with the wrong nutrient level outweighs the benefit of eating plants that are the right nutrient level.”

So, what if we mix it up more when planting the garden? Perhaps this person’s planting scheme would work for some people. No planting a pest feast happening here:


High diversity or interspersed planting, better approach to control garden pests with plants

Not much genotype duplication in this garden. (Thomas Generazio)


Even though our scale is tiny in comparison to a farm field, we are still sowing exact copies of the same plant shoulder to shoulder in rows and patches. If it’s a feasible suggestion for farmers, then the idea has some merit. Maybe we should be growing three different varieties of the same thing in that 10 foot long row instead of one. It certainly would offer a natural means of prevention versus our normal reactionary approach to stopping the damage.

Yes, for some it means buying more seed than they’re planting. But when stored properly, that seed is viable for at least 2-3 years, if not longer. And it could mean spending less on biological control and imported predator insects. If you can control garden pests with plants, it’s certainly less labor intensive than running around with a sprayer! And less stressful than praying it doesn’t rain too soon after you got the chance for application. Maybe shared ordering co-op to keep costs low for financially challenged growers.

But the study included 53 insect pest species from all those nuisance families – caterpillars, beetles, aphids, flies, etc. However, it’s possible this approach works better for some types of fruits and vegetables than others.

Take brassicas, for example – cabbage, broccoli, brussel sprouts, and cauliflower. It’s almost impossible to grow these without some form of pest control, even if it’s provided by row covers. But Chinese Cabbage has excellent pest resistance. Is it possible to gain control by interspersing this between the others? No one will know for sure until it is tried. Some cabbage pests are drawn to green leaf varieties, while others have a decided preference for the reds. So, what happens if you mix it up even more by rotating the row planting with red, Chinese, green, Chinese, red… and so on?

And then there’s corn earworm. Varieties with tight husk have good resistance, and the best corn patch comes from planting two types. Therefore, it seems that sowing one variety in one half, and the other in its own section is the wrong approach. Perhaps better earworm control is possible with interspersed sowing.

So garden planning, planting, and seed ordering is more complex. A task that means weighing the possibilities for each different crop type you grow. But in exchange for less growing season problems, the effort would pay off. From a risk analysis point of view, the way humans plant food screams high risk. And the bugs have the best odds. Could the centuries old system be the very cause of the problem? Look at it as outfoxing the enemy with guerrilla tactics. As opposed to this never ending situation of sending your troops in organized rows and regiments straight into the stream of arrows and cannon fire you know is coming every summer.

Food for thought, if not an interesting experiment project for next summer.


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The garden played a starring role from spring through fall in the house Amber was raised in. She has decades of experience growing plants from seeds and cuttings in the plot and pots.