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Natural Pest Control – North American Survey Worth Revisiting

I just had a lovely phone call with my sister. One discouraging note was her recent decision to finally give in and purchase some pesticide spray. (She’s usually a greenie, but as she put it, “I just want to have some plants.”)

Her tomatoes and other starts have been eaten down to little nubs several years running, despite trying various methods like beer traps and soap sprays. She’s in sunny southern California, so the tricks we learned in our mother’s garden in rainy Oregon may not entirely apply.

I was concerned of course. Not only on principle (I myself will accept garden failure or eat grasshoppers before I would spray chemical pesticides) but also from the heart, because I love my sister and her family. Their branch of my extended family is already dealing with a restricted diet due to food allergies, and the chemical and social pressures of the greater Los Angeles environment.

Looking for online resources, I found the following excellent article from Mother Earth News, circa 2011, based on a survey of gardeners from all regions of North America:

For North American readers this info seems well-researched, and has loads of useful links to sub-articles on beneficial insects, specific species and tactics, differences in results between different regions, and more. Some key pests from other regions may not be mentioned, but many of those described are common garden pests worldwide. Having lived in both regions, I can verify that slugs are the #1 pest in the rainy Pacific NW, while grasshoppers are a bigger issue in the inland / Rockies region.

Controls like hand-picking and Bt show up as very effective on many pests. Other simple steps like rigid collars or row covers are also popular. Beneficial insects and companion planting get mixed results (they’re harder to target, after all), but there are some fascinating suggestions. All the recommendations are based on responses by actual gardeners, not university test plots or industrial farmers.

Now for the doom and gloom side of the argument:

Here’s an article highlighting some problems of the pesticide approach:

The biggest concerns I have in my sister’s case are:

  1. Bioaccumulation – pesticides concentrate in foods, body fat and breast milk, and I would prefer that my young school-aged nieces get as little exposure as possible. These are mostly food plants she’s trying to protect.
  2. Diminishing effects – my sister wants to spray “just for the first few weeks” to get the plants established, but most pesticides breed resistant bugs, and they can also reduce the health of the plants encouraging further infestation. It’s possible that some of her current problems can even be traced to residual pesticides or herbicides from previous property owners, creating ill health for the plants.
    She will be embarking on the pesticide ‘treadmill’.
  3. Just plain ignorance. Most pesticides aren’t well labeled, and many are not well-tested for long-term, cumulative health effects either in humans or for wildlife and soil biota. I have spent four years teaching basic chemistry, and I doubt I could tell my sister whether her chosen pesticide is “safe.” She has an art and communications degree, and while she’s no dummy, there is simply no way for her to know until it’s too late… and even then, the level of knowledge available will likely still be a labyrinth of doubts rather than a definitive problem and cure. The best cure is prevention: if you don’t know what’s in it, and what those words mean for your long-term health, don’t use it.

I can’t make my sister’s choices for her, but I can find the best resources and make the information available. Hopefully with access to info on specific pests and effective, non-poisonous control tactics, she’ll find those mysterious chemicals are not necessary after all.


  1. A couple of years back a locust plague kicked off to the north of here and worked its way south through the farm here. All that happened was that the local birds had a massive protein hit in their diet for a week or so and I spotted a few locusts bouncing around in the sunlight.

    Generally I reckon insect predation is a sign of a lack of plant and animal diversity in a garden and/or the surrounding area. Mono cultures provide excellent food sources for large populations of specific insects which take advantage of an easy and very large food source.

    It may be difficult to achieve in all locations, but the long term solution is to have a large diversity of plants (ie. a poly-culture) in a productive food system. This will in turn provide housing and shelter for an ever larger number of diverse insects, frogs, reptiles, animals and birds, who in turn will eat those insect pests without your assistance.

    Will they eat some of your produce? Yes, but they will save you a whole lot of hassle and work. It is easier and cheaper to simply grow a bit more produce to allow for this. The other benefit is that if you feel strongly about it, you’re not sending your resources to support the chemical industries. Mono culture agricultural practices are very difficult without constant inputs such as fertilisers and pesticides. I feel from them as it is a tough gig.

  2. Hard to get the diversity in the garden to deal with pest problems if you live in an area like Los Angeles. I think we’ve come to realize pests and disease problems that are severe enough to destroy an entire crop are just a symptom of an underlying problem. The problem in her case is rather than fighting the bugs asking why they are there to begin with. I suspect her garden soil is either deficient in either major essential minerals (calcium, phosphorus) or minor (zinc, boron etc) or they are there but unavailable due to a number of reasons. I think everyone who gardens owe to themselves to get a good soil test both for the health of the plants and your health since your eating them. A CEC (cation exchange capacity) test for base saturations and a reading of plant availability like the La Motte test are an excellent place to get started. I’ve had good success following recommendations given by Crop Services International, a testing company.
    Classic permaculture example of chicken/duck interaction will help enormously too, kept in perimeter location.

  3. Hi Alby,

    Of course you are correct too. Healthy, nutrient dense plants are less likely to suffer from insect predation. Good point too in identifying that this all starts with the soil. As an interesting side note, I recycle every scrap of organic matter that works its way onto this farm into the top soil including humanure. Excellent point.

  4. This year i read in a forum about organic gardening in Germany, that someone made a little experiment in his garden. She planted plants in soil which was treated with the usual methods by the antecessor: fertilizers and pesticides. In the beginning of the first year she just sowed phacelia and buckwheat ( Fagopyrum esculentum ). The soil wasn’t dug over but just superficialy loosened up. In the following winter the garden was mulched with grass clippings and with the rest of the green manure. These mulch layer is renewed every time there is some organic matter to deposit.
    The follwing year all the snails (slugs?), which are not decimated “especially” with slug pellets, have eaten up especially “foreign” plants. She had self planted salad (direct seeding) and some bought salad seedlings. The seedlings were all eaten up, even within the rows, but the direct sowed salad shows not a single bite of a slug.

    She thinks, that it’s because of the smell of putridity which comes from the soil wich attracts all the slugs and the foreign plants most probably also grew up in a putrid soil.

    Elaine Ingham published a revolutionary fact in the following discussion:

    Topic: soil chemistry facts (49 Messages) Aug 27, 2004

    Teaching the Soil Biollgy and Soil Chemistry course with Dr. Lancaster here at Southern Cross University, and we are showing some very interesting relationships between soil chem and soil biol.

    Did you know that NO AGRICULTURAL SOIL lacks the NUTRIENTS needed to grow plants?

    Maybe one or two rare exceptions to that rule when we get into non-ag [agriculture] soils, but any soil used for agriculture does not lack the nutrients needed for plant growth.

    We calculated how many years’ worth of phosphate was actually present in wheat filed soil in Australian, soils where growers have been told they needed to add thousands of dollars of PO4 because there was no phophate present. There was 15,000 years worth of phosphate present in that soil (something like $48,000 worth of “fertilizer”), if that phosphate could be made available to the plants.

    So, no soil on earth lacks any nutrients, the soils only lack the biology to free the locked minerals, especially organisms which can dissolve rocks like lichens, fungi, diatoms and cyanobacteria.

  5. I’m going to respectfully disagree with Ms. Ingham on that one. While it’s true plants will “grow” on any soil and plants adapt to the deficiencies of their area, to have optimum health, disease resistance, pest resistance and be the healthiest for the HUMAN eating them the soil must have the elements in not only good supply but also balanced with each other. In fact I’d say the opposite there is hardly a soil that ISNT deficient in at least some major or micro element. While it’s true a lot of soils suffer from unavailability due to low biological activity, ph etc to say no soils are deficient is pure rubbish. Any CEC (cation exchange capacity) base saturation soil test will show otherwise and if you look at the work of Dr William Albrecht he shows very clearly how different soils affect the quality of forage grown and its nutritional value to animals eating it. He showed also that soils in areas with higher rainfall then evaporation, unless resupplied with rock or silts are actually losing nutrients to leaching faster then they are replaced leading to wide spread deficiencies of elements. If every soil had the same composition they would all grow the same plants and animals! That is obviously not the case and soils vary enormously in nutrients. Soil composition dictates what grows, plants are not the cause of soil conditions for the most part. This is why the buffalo roamed in the midwest and trees grow in the east in the U.S.

  6. NO AGRICULTURAL SOIL lacks the NUTRIENTS needed to grow plants … the soils only lack the biology to free the locked minerals, especially organisms which can dissolve rocks

    Question 1: If you have with a great deal of SOM, where are the rocks?

    Question 2: If you make gardens especially raised beds, hugelkultur or otherwise, where are the rocks?

    Question 3: If you have rocks, is the natural mineralization process equal to or faster than the constant ongoing extractive process of growing food?

    Dr. Ingham is right in general terms, ie, get the microbiology going but I think not in specific terms, ie, you’d better replace what you take out by remineralizing with rock dust.

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