*Shannon wrote this article for Rural Delivery magazine, one of our favourite magazines. Check it out if you’re not already a subscriber!
Every so often, a customer at the farmers’ market asks me about pesticides. They know I’m an organic farmer and they’re specifically asking because they’ve heard there are pesticides allowed on organic farms.
First of all, what is a pesticide?
It’s anything that is used to kill a pest. A pest can be a type of bacteria or fungus, an insect, a rodent, a mammal like a deer or coyote. A pest can be a plant like the annual lambs’ quarters or perennial glossy buckthorn. A pest can even be a person (though recommendations to rid you of that type of pest are for a different article). A pest is simply any organism that you’re not happy having around.
Pesticides are therefore a very large category and can be broken down into sub-categories. For example, an herbicide is a type of pesticide that focuses on herbs (or plants) and an insecticide is a pesticide that targets insects.
There’s a saying that when you remove a predator, you must take on the ecosystem role of that predator. Farms inevitably change the ecosystem and you end up losing some predators. And then you need to do their job, which often is not much fun. I know I prefer my hard-working (and cuddly!) farm cats to setting and cleaning out a bunch of mouse traps.
So, does Organic mean ‘No Pesticides’?
Organic can mean that no pesticides are used. On my certified organic farm, I don’t use any pesticide products (including ones allowed on organic farms…..we’ll write a future blog post on why), and there are many others like us. But overall, organic (with respect to pest management) means that you do everything you can to avoid using pesticides. And as a last resort, there is a list called the Permitted Substances List (part of the Canadian Organic Standards) with ingredients an organic farmer can use. Sometimes these products are called Organic Pesticides which isn’t an accurate term, but I’ll use it because it’s easy.
Organic Pesticides include plant-based pesticides, minerals, and biological organisms such as bacteria, fungi, insects and nematodes like Bacillus thuringiensis (Bt) and spinosad.
As an organic farmer, you need to prove to your inspector and certifying body that you tried other things to prevent the pest outbreak before you resorted to the Organic Pesticide.
So what can you do?
There are plenty of strategies and new ones are being trialed all the time.
Crop rotation: Moving the same crop (or same crop family) to a different part of your farm each year (or in some cases, within the same year), is a technique for avoiding and confusing pests. We’re so lucky here in Atlantic Canada that we get cold, snowy winters and many pests can’t survive them. But we still have quite a few pests that can, so moving their favourite crop to a different location makes it harder for them to find.
Soil and Fertility Management: Building soil health and managing the fertility of your soil helps to grow healthier plants that can better resist pest pressure. For example, aphids love plants growing in soils with excessive nitrogen – which often occurs in early spring hoophouses. We’ve so far avoided aphid pressure in our high tunnel by not adding any nitrogen-rich fertility (like compost or crab meal) in the fall or early spring.
Resistant seed varieties: Many seed catalogues list the pests a variety has been shown to resist, especially with disease pests. Locally-grown seed can be a good option since it’s often selected from the plants most resistant to local diseases. There’s growing interest among plant breeders to work with organic farms to see which plants are more resistant to pests that are commonly sprayed for in non-organic systems. I’ve also heard of renewed interest in selecting for varieties naturally resistant to insect pests like flea beetles and squash bugs. Exciting stuff!
Research: What is going on in your farm ecosystem that has allowed this organism to reach pest status? Learn your pest’s life cycle, its predators, and even the benefits that pest can offer when it’s not out of control. For example, some pests prefer living around a mulched crop while others are deterred or confused by it. Knowing that flea beetles move by hopping led us to cover our radishes using row cover without supportive hoops, to reduce the vertical space for any flea beetles underneath to prevent them from hopping (and damaging crops) throughout.
Attract predators: Creating habitat for the predators of your pests can attract them and keep them on your farm. Some farmers purchase and release certain beneficial organisms including insects, like ladybugs (especially for enclosed greenhouses), but remember that they’ll need more than that one pest to eat in order to thrive for long.
Physical exclusion: On our farm, we frequently use row cover and netting to protect crops from insects. While this netting definitely costs more than buying a one-time application of a pesticide, I like knowing it’ll be used for many years. Organic farmers can also use kaolin clay (there’s a product called Surround WP) which physically deters insect pests like cucumber beetles, flea beetles or thrips from feeding (also prevents sunscald on fruit).
Some farmers say, “We’re not certified organic, but we only use Organic Pesticides.”
I appreciate that though it isn’t the same as being organic. Farming organically isn’t just about substituting ‘conventional’ pesticides for Organic Pesticides. Organic Pesticides are only allowed as a last resort on organic farms and organic farmers who use these pesticides need to first check with their certifying body regardless of whether the pesticide supplier says it’s approved for organic use. Organic farmers can’t necessarily use them every year, they might need to show soil test results first, and not every listed use on the product label is ok for organic use.
Organic farming is often referred to as knowledge-intensive, because there is no set formula or playbook to follow. It’s all about the ecosystem of that particular farm. It’s about encouraging life – in all its various and messy forms, which isn’t easy for us humans in our frequent quests for control and perfection.
Sidebar: Permitted Substances List
The latest revision of the Canadian Organic Standards came out in 2015. You can find the new Permitted Substances List (or PSL for short) for free online.
Instead of writing about all the ingredients that are permitted, I’m going to focus on the ones I’ve heard the most questions about. Just because an ingredient is permitted, doesn’t mean that every product containing it will be allowed for organic use. Brand name products also contain ‘inert’ ingredients that may or may not be permitted.
Bacillus thuringiensis (or Bt for short): There are different strains of this naturally-occurring bacteria. Btk (var. kurstaki) is popular among organic farmers and is effective against a wide range of Lepidoptera (caterpillars). It is considered harmless to virtually all other creatures. With both the topical use (spraying) and systemic use (GMO), there are concerns around the development of pest resistance (some populations of diamondback moth have already shown resistance) and effects on non-target insects, like monarch or other rare butterflies or moths (though the Bt must be ingested to work).
- Spray: Btk is frequently sprayed on Brassicas (cabbage, broccoli, cauliflower) in the late summer when all the caterpillars that love them are at their worst. DiPel is a commonly used product.
- GMO: Bt has been inserted in some genetically engineered crops. In Canada, Bt corn is grown and the Bt is present in the plant matter itself. This exposes the insects to the Bt toxins throughout all parts of the plant during the entire growing season and after the crop is plowed under. Organic farmers cannot plant any GMO crops.
Spinosad: Is a chemical compound produced by the soil bacterium Saccharopolyspora spinosa. It’s shown favourable control for thrips, leek moths and many caterpillar pests. While it is considered to have a low toxicity to mammals, it is toxic to some beneficial insects (like bees, parasitoids, predatory mites) and aquatic invertebrates like mollusks. Entrust is a popular brand name for organic farmers.
Copper: A necessary mineral for humans and plants in very small doses and naturally-occurring in soils (though often very low in Atlantic Canadian soils). A heavy metal, it does not degrade, persists in the environment, and inhibits naturally-occurring organisms on leaves and in the soil. Problems arise with buildup in the soil and so organic farmers using copper for bacterial or fungal pests (for example, bacterial spot or late blight) should monitor with soil testing and practice crop rotation. Particular care must be taken in non-rotation areas like high tunnels or orchards. Copper is highly toxic to fish and aquatic invertebrates, can be toxic to bees, earthworms, sheep, and chickens and has been linked to liver disease in vineyard sprayers after years of exposure. Bordeaux mix is a combination of copper sulphate and hydrated lime.
Sulphur: Sulphur products (including lime-sulphur), like copper, have low potential pest resistance, and are considered preventive fungicides. It’s most widely used against powdery mildews. Less persistent in the soil than copper, it can be toxic to beneficial insects and to plants, at varying levels according to the species, especially at high air temperatures or when mixed with oil products. It is sometimes alternated with copper to prevent build-up.
Pyrethrum (aka Pyrethrin): Made of the dried flower heads of Chrysanthemum species called pyrethrum daisies, it acts on many sucking and chewing insects like leafhoppers, flea beetles, and thrips, as well as beneficial insects. While it’s toxicity to mammals is very low, it is slightly toxic to birds and very toxic to fish so must not be allowed to contaminate waterways. Pyganic is a brand name product used by organic farmers.
Rotenone: In Canada, rotenone products are no longer registered for agricultural use, including on organic farms. A plant derived broad-spectrum insecticide (occurring in the roots and stems of a small number of subtropical legume plants) that was once used as an alternative to chemical pesticides. It is toxic to cold-blooded animals including fish, and other animals including pigs. Rotenone kills by attacking mitochondria, the energy powerhouses of all living cells. Research found that exposure to rotenone caused Parkinson’s disease-like symptoms in rats and correlated with a higher incidence of Parkinson’s disease in humans.
A Whole-Farm Approach to Managing Pests bulletin, http://www.sare.org/Learning-Center/Bulletins/A-Whole-Farm-Approach-to-Managing-Pests.
A Total System Approach to Sustainable Pest Management, http://www.pnas.org/content/94/23/12243.full
Organic Agriculture and Integrated Pest Management: Synergistic Partnership Needed to Improve the Sustainability of Agriculture and Food Systems https://organicipmwg.files.wordpress.com/2015/07/white-paper.pdf
Resource Guide for Organic Insect and Disease Management http://web.pppmb.cals.cornell.edu/resourceguide/.