Shifting our attitudes towards pesticides

By Nir Oksenberg

9.6.15

The worm [not] in the apple

Our gut feeling tells us that pesticides are dangerous. Why is that? When I eat an apple, I savor its cool crispness, honey-like sweetness, and wholesome nutrients. I imagine somebody planting a young tree in the ground. A combination of water, sunlight, nutrients from the soil, labor and time allowed me to enjoy the fruit.

 

Does that perception of the apple change when we learn that apples require the use of pesticides? Pesticides often invoke images of a skull and crossbones and somebody in full protective gear spraying fields. It is not difficult to understand why people prefer pesticide-free produce. But what exactly is a pesticide? How much do we use and how necessary are they? What molded our perceptions of pesticides? We shouldn’t always listen to our gut feelings.

 

In 1500 B.C., Sumerians rubbed sulfur on themselves to ward off insects1. Today, we still rub pesticides on ourselves, albeit, better smelling ones. For example, if you use antimicrobial soap, you are scrubbing on pesticides.  Despite frequent household uses including garden supplies, pesticides are often associated with agriculture.

 

Agriculture originated more than 10,000 years ago, in the Fertile Crescent of Mesopotamia 2. Crops concentrated in one location provided more food, but also attract pests at levels that threaten food supply. In approximately 300 B.C., Theophrastus was the first to write about crop pest damage. Theophrastus, the father of modern botany, reportedly killed young trees considered to be pests by pouring olive oil on their roots. He also noticed that certain pests associate with certain crops 1. Crop protection did not become wide spread until Europe’s agriculture revolution in the 1700s and 1800s. Substances like copper, copper sulfate, lime, chrysanthemums, oils, lead, mercury and arsenic became popular ingredients used to control pests. In the 1920s, pesticide use became more ubiquitous with the use of planes to spray pesticides onto fields from the air. In 1962, Rachel Carson wrote the book Silent Spring. This lead to mass public awareness of the use and potential dangers of synthetic pesticides.

 

While many modern pesticides are synthetic, farmers have used natural pesticides for centuries. Some of these, including mercury, are highly toxic. Plants also produce their own natural pesticides to defend themselves. In 1990, Bruce Ames, published a paper entitled “Dietary pesticides (99.99 percent all natural)”. He calculated that we eat about 1.5 grams of natural pesticides every day. This amounts to “about 10,000 times more than the amount of synthetic pesticide residues we consume.” This list of natural pesticides contains some favorites – caffeine, nicotine, capsaicin in peppers, and pulegone in peppermint. Understandably, even though we consume many more natural pesticides, the idea of synthetic pesticides is harder to stomach for the average consumer.

 

What does 877 million pounds really mean?!

Our distrust in synthetic pesticides is rooted in our inability to interpret the many disembodied facts and figures given to us. Statistics on the use of synthetic pesticides are difficult to decipher and often misleading. For example, the United States used 877 million pounds of pesticide active ingredient in 2007. But, to understand what this number means, you need information on crop yield, environmental toxicity and persistence, consumer and user safety, application rates, number of acres treated, and other factors. For instance, a report finding that our use of all herbicides increased by millions of pounds in the last few years alone sounds bad. Nobody wants millions more pounds of chemical pesticides on our farm lands. If the report also reveals that while we have increased our net use of herbicides, we have been using significantly less toxic and persistent ones resulting in a net decrease on environmental impact, this more sophisticated knowledge might influence the interpretation of this number. While researchers collecting and analyzing pesticide use do carefully consider many factors, the results reported to the public by other sources are too often misrepresented. These soundbites are used to peak reader’s interest, but rarely communicate a precise reflection of actual amounts, effectiveness, or impacts of pesticides.

 

A world without pesticides

Given the public’s negative perception of pesticides, why are they still so ubiquitous? How necessary are they? Even with pesticides, insects and fungal damage destroy about 42% of the world’s crops. Without pesticides, we would lose an estimated 70% of the world’s food crop 3. Include environmental factors like droughts or floods, and we would be facing a global food crisis. To feed everyone, we would need at least 90% more cropland 4! This would lead to serious environmental threats including habitat loss, water consumption, soil erosion and degradation, and pollution. Also consider the vast increase in the number of laborers we would need to destroy weeds by hand without the use of herbicides. The Crop Protection Research Institute predicts the need of an additional 70 million workers in the USA alone.

 

Our reliance on pesticides is not an excuse for improper use. Pesticides can be overused as the primary method for controlling pest populations, as they work well and are relatively inexpensive. Yet, other methods such as biological controls (use of natural enemies), cultural controls (such as irrigation practices), and mechanical/physical controls (such as traps and mulches) are available. The most effective and sustainable way to control pests is a combination these tools. This is known as integrated pest management (IPM). IPM aims at managing pests while minimizing risks to people and the environment. IPM focuses on long-term prevention of pests. However, this approach often requires extensive research and understanding of ecological systems including pest life cycle and population dynamics. If we want to reduce our use of chemical pesticides, but not sacrifice yield or use more farmland, we need to invest in this research.

 

“Civilization as it is known today could not have evolved, nor can it survive, without an adequate food supply” –Norman Borlaug

Instead of demonizing the chemicals farmers use to safely produce food, we need to encourage their continued proper, regulated use. We need to further identify ways to decrease their necessity by combining them with other practices. We need to keep things in perspective. Yes, pesticides can potentially cause harm to humans. But an adult male can eat 571 servings of apples in one day without any effect from pesticides, even if the apples have the highest pesticide residue recorded for apples by the USDA. Yes, the use of some types of pesticides (such as herbicides in some crops) are increasing, but we are growing more acres of associated crops. At the same time the environmental toxicity of these herbicides is decreasing 5. Yes, there are serious threats caused by overuse of pesticides, including off-label use, the development of pest resistance and other real concerns not discussed in this article. But with good practices, we can manage these problems.

 

The next time you wash a fruit or vegetable and find yourself thinking about pesticides, try to keep things in perspective. Remember the 1.5 grams of naturally-produced pesticides in those foods. Remember that the dose makes the poison. A typical exposure to pesticides in our diet is at levels of 10,000 to 100,000 times lower than those considered risky to our health 6. Consider how the judicious use of pesticides enabled the production of more food on the agricultural land used to grow your produce. Know that farmers are increasingly educating themselves about IPM. Farmers are using a variety of techniques including crop rotations, the planting of disease resistant varieties, biological controls, and environmentally benign pesticides to produce food. Know that your apple is safe to eat, and eat it confidently knowing you don’t need to pull out a juicy worm.

 

  1. Taylor, E. L., Holley, A. G. & Kirk, M. Pesticide Development: a Brief Look at the History. South. Reg. Ext. For. SREF-FM-01, (2007).
  2. Kislev, M. E., Weiss, E. & Hartmann, A. Impetus for sowing and the beginning of agriculture: ground collecting of wild cereals. Proc. Natl. Acad. Sci. U. S. A. 101, 2692–2695 (2004).
  3. Pimentel, D. Pest Management in Agriculture. Tech. Reducing Pestic. Use Econ. Environ. Benefits 1–11 (1997).
  4. Trewavas, A. J. The population/biodiversity paradox. Agricultural efficiency to save wilderness. Plant Physiol. 125, 174–179 (2001).
  5. Brookes, G. Weed control changes and genetically modified herbicide tolerant crops in the USA 1996–2012. GM Crops Food 5, 321–332 (2014).
  6. Beall, G. A., Bruhn, C. M., Craigmill, A. L. & Winter, C. K. Pesticides and Your Food: How safe is ‘safe’? Calif. Agric. 45, (1991).

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