One principal “advantage” of organic food over genetically modified, conventionally grown crops is that organic food supposedly is free of pesticides. For example, last spring, Consumer Reports released “From Crop to Table Report,” has a section headlined, “Organic: Farming Without Pesticides.”
But the headline–promoting a widespread myth about organic farming–is flat out not accurate. The truth is, organic farmers use both synthetic and natural kinds of pesticides —with approval under the USDA Organic Act.
In fact, Consumer Reports backtracked from its misleading headline in its article, noting that natural pesticides — which are not necessarily safer than synthetic ones and often less targeted to protect beneficial insects — are common. It writes: “Federal law prohibits the use of almost all synthetic pesticides on organic farms.” It then stumbled again in its summary, writing, “Only 10 synthetic insecticides are approved for use on organic farms.”
Consumer Reports is typical among ideological organizations — promoting the misconception that organic farming can somehow magically control pests without using chemicals. Some specific chemicals are not approved for use on organic farms, including organophosphates, glyphosate, atrazine, and methyl bromide. But a surprisingly high number of pesticides are allowed. And now, a number of organic farmers are asking the federal government for permission to use more synthetic pesticides
Long list of organic pesticides
The USDA National List of allowed pesticides for organic growers is quite long. The list includes some substances that one would assume would be relatively harmless, such as mulch, dairy cultures or vitamin B. But others on the list should raise eyebrows: Copper sulfate, elemental sulfur, borax and borates are all known to cause some harm to humans and are approved members of the organic list. Among “synthetic” pesticides, pyrethrums are still allowed, and Vitamin C that is chemically derived (and therefore synthetic) is allowed, as are various forms of alcohol.
Whether “natural” or “synthetic,” these chemicals have unintended side effects. As to safety differences between the two categories, “You can’t generalize that broadly,” said Rob Wallbridge, an organic farmer in Quebec, Canada. “Every pesticide has a different profile, and there are many different ways to define safety.”
Acute toxicity (measured by half of a lethal dose, or LD50) is very often used, but rates of exposure, persistence in the environment, chronic chemical effects, and impact on off-target animals and plants also are important considerations. One criticism of organic pesticides, in fact, is that a farmer has to use a lot of them to get the same effect as conventional pesticide. If it’s true that “the poison is in the dosage,” then some organic pesticides (like sulfur or copper) do not look very benign.
What pesticides are used most often in organic farms?
- Bt (the bacterium Bacillus thuringiensis) is the most widely used pesticide, accounting for 90 percent of the organic pest control market. Ironically, Bt is also engineered into many GMO crops to express the Bt Cry protein (for example, Bt cotton, Bt soy, Bt corn), but is attacked by anti-GMO extremists as being ‘dangerous’)
- Spinosad, an insecticide derived from soil bacteria (and can cause some irritation and redness with direct contact, according to the National Pesticide Information Center), is also very popular on organic farms.
- Lime sulfur also has been used as a fungicide on organic crops. However, the EPA restricted its used in 2008 so that only professional pesticide appliers could use it. The reason? It was too caustic, capable of causing burns.
- Kaolin clay, which provides a physical barrier to sun damage and to insects.
What about the potential for collateral damage to beneficial insects?
Anti-GMO activists have repeatedly claimed that certain chemicals, including the herbicide glyphosate in conjunction with Bt-modified corn and other crops, have been responsible for reducing populations of bees, butterflies and other “non-target” species. While recent studies have challenged these claims. It’s been documented that certain organic pesticides can kill these species. According to the Xerces Society for Invertebrate Conservation, organic-approved pelylysticides including Beauveria bassiana, a naturally occurring fungus, diatomaceous earth, insecticidal soap, horticultural oil, pyrethrins, rotenone (another organic-approved synthetic which is now banned), spinosad, and copper sulfate can be very toxic to bees.
Surprising chemical loophole
In addition to these pesticides, organic farms are, in certain circumstances, permitted to use chemicals that are supposedly banned for organic use. One of these is methyl bromide, a fumigant that is used to boost strawberry growth. Although use of methyl bromide was banned several years ago, conventional growers can still use it if no viable alternatives are available. But organic farmers can also use it, for largely the same reasons. For “perennial planting stock,” those plants that are grown throughout the year, there aren’t many organic sources of the initial seedlings. So, organic farmers are allowed to use non-organic strawberry plants, complete with methyl bromide injected into the ground, and grow them as “organic” strawberries, as long as the plants are replanted and/or organically managed starting a year before harvesting.
No farmer likes pesticides. If it were possible to grow food without them, nobody would hesitate. But this isn’t possible around the world. But for anti-GMO activists to point at organic food as a “pesticide-free” alternative to genetically modified food is inaccurate at best. In fact, pesticide use overall has dropped, as much due to genetically modified foods as to better tillage and other farming practices. And not because organics are “pesticide free.”
Andrew Porterfield is a writer, editor and communications consultant for academic institutions, companies and non-profits in the life sciences. He is based in Camarillo, California. Follow @AMPorterfield on Twitter.