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Why can’t we farm without chemicals like my grandfather did?

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This question came up in an Internet discussion last week, and it is really an interesting question. Let’s assume your grandfather is 60 years older than you are. This would take you back to around 1950. And if your grandfather was farming in 1950, he was using a lot of agricultural products on his farm. Despite the bucolic image of farming, it is terribly hard work, and farmers were pretty quick to adopt any new products that looked like they would make the job easier. And in the 1950s, insecticides and fertilizers were very common indeed.

To look at the history of this in perspective, we need to go much farther back than 50-60 years. Records show that sulfur was used as a pesticide by the Romans in 2000 BC, and by 100 BC, they were using extracts of hellebores (ranunculus) for insect control.

We know from colonial records that they were using nicotine (extracts of tobacco) as an insecticide as early as 1690, and rotenone was extracted from jicama and other plants as early as 1848 and used as an insecticide and to kill fish.

But the first real manmade pesticide came about in France quite by accident. In the Bordeaux region of France, growers had taken to spraying the grapes near the roads with a mixture of copper sulfate and lime to keep pilferers from stealing the grapes. It was bitter tasting and easily visible from the road.

However, this was a period when downy mildew was a serious problem on wine grapes, and botany Professor Pierre-Marie-Alexis Millardet of the University of Nancy noted that grapes near the roadway did not seem to be affected by the downy mildew. It was clear that the copper sulfate/lime mixture acted as a fungicide, and it was dubbed “Bordeaux mixture.”

As Dixon notes, this was hardly an accidental discovery. Millardet developed the exact proportions and techniques for applying Bordeaux mixture through extensive experimentation. It is also interesting to note that this historical compound is highly poisonous and has been replaced by much safer and more effective fungicides today. Nonetheless, the organic growing industry insisted that it be allowed to continue to use it over newer, safer methods even though the EU had planned to ban it in 2002.

Millardet was also responsible for finding a way to battle the Phyloxera pest that was decimating the wine grapes in France, and for these two major accomplishments he could have been as famous as Petri or Bunsen had he been any sort of self-promoter.

Phyloxera, a sort of aphid-like pest, was accidentally introduced to France from the US where it was much less of a problem. Millardet and a colleague controlled the spread of phyloxera by grafting French grapevines onto American rootstock, creating a grapevine that was resistant to the bug, thus saving the French wine industry.

Farming in the 19th Century

My great-great grandfather, William A Cooper, emigrated from Wolverhampton, England to the US in 1840, settling on a small farm on land near Pittsburgh in what is now Oakmont, PA. We don’t know exactly how small it was, but the tax rolls showed it valued at $240, much less than the neighboring farms. Nonetheless, he and his family farmed this land successfully until nearly 1890. This was most probably what we’d call a “subsistence farm,” where they fed themselves, but probably had little excess crops or livestock to sell. This was the most common mode of farming in the 19th century although larger farms began to spring up by 1900.

In early farming, it was common to rotate crops between at least corn and alfalfa, so that the nitrogen required by the corn would be replaced by the legume, alfalfa. Sometimes farmers rotated through three or four crops, giving the soil a chance to rebuild.

Insecticides in the late 19th century were catch as catch can affairs, and mostly didn’t work very well. Some farmers tried to chase away bugs by dragging logs around the perimeter of the field and filling the resulting trenches with kerosene, tar and the like. Arsenic based poisons like Paris Green (copper arsenite) and London purple, an arsenite of lime. Both were by-products of dye manufacture, and while they were marginally successful at insect control, they were quite poisonous to humans and led to some deaths among the hired hands, and eventually among a few consumers. This led to the banning of the arsenites, which actually didn’t work all that well.

But the main transition in farming took place in the 1930s, when farmers were only 21% of the populace compared to 93.3% in the 1790s. Under these conditions, farmers began to specialize in single cash crops, leading to broad swathes of farmlands growing much the same crops. This quickly became an ideal “salad bar” for insects, and the pest problem became much worse.

In the 1930s, farmers were using:

  • Arsenicals, 80-90 million pounds
  • Sulfur, 73 million pounds
  • Kerosene, 10 million gallons
  • Mineral Oil Emulsion, 40 million pounds
  • Naphthalene and paradichlorobenzene, 21 million pounds
  • Pyrethrum, 10 million pounds
  • Nicotine sulphate, 2 million pounds
  • Rotenone, 1.5 million pounds

In addition, as international commerce increased, insects began to arrive from foreign shores who had no local natural enemies. Among those were San Jose scale, which was discovered in San Jose in 1881, but had probably come from China on some imported fruit trees. While there were natural enemies that could be imported in a few cases, overall, it was the vast number of immigrant insects that farmers had to deal with that turned them to chemical controls.

This took place much more effectively after World War II, with the introduction of DDT to farmers and the development of many hundreds of other similar insecticides. They were cheap, effective and seemed at first to be relatively harmless (to humans). However, as we now know from Rachel Carson’s writings, some of these early insecticides bioaccumulated and had substantial environmental effects. Carson’s book contained a number of exaggerations and assertions that turned out not to be true, but it did raise the consciousness of a whole generation of farmers and consumers about the safety and effectiveness of some of the chlorinated organics like DDT, and resulted in its banning in the US. DDT remains an important tool in fighting malaria and is still legally used in many tropical countries. The EPA also completely banned chlordane and heptachlor in 1973 because of their carcinogenicity.

In the US, however, this resulted in the introduction of considerably less toxic pesticides including Bt, as well as the reduction in the quantities used. Savage has detailed this reduction in toxicity recently.

So, if you grandfather farmed anytime since the late 19th century, he certainly used pesticides, and if he is farming today, he probably is using a lot fewer pesticides and most likely using ones that are considerably less harmful to humans and the environment.

Fertilizers

Early farmers either rotated crops between heavy feeders like corn and restoring crops like alfalfa, or they simply moved to new ground once the land had become depleted. Of course, they also used whatever available manure they had to enrich the soil, but the amount of manure they really needed was often more than they could obtain from their livestock.

At the same time, farmers were trying to increase the yield of their crops, particularly of cash crops such as corn. As Crow points out, the usual approach was to select the tallest, strongest ears as seed for the next year’s crops. However, this became less and less successful over time, because their corn was becoming inbred, and successive generations slowly became weaker.

G.H. Shull was born in 1874 into a family of sharecroppers, where he was one of eight children. Because of the demands of farming, he had little time for education and was largely self-taught. He did manage to work his way through high school and ended up teaching in a country school for a couple of years. Then, he went to Antioch College, where he worked as a janitor while studying, and managed to graduate near the top of his class. He received his PhD from the University of Chicago and joined Cold Spring Harbor Laboratory with some of his Chicago colleages.

As early as 1876, Charles Darwin pointed out that inbreeding produced weaker plants, while cross-breeding produced stronger ones. However, once Mendel’s laws were rediscovered in 1900, the reasons for this became obvious.

But it was Shull who pointed out in 1908 that hybrids between two inbred lines restored the original plants’ vigor. This eventually led to the idea of 4-way crosses between the crosses of two inbred lines, and that is the methodology that Henry Wallace used to develop his first commercial hybrid seed. Later, techniques for predicting which crosses would be more productive allowed breeders to produce equally productive hybrids using just single crosses. These hybrids were stronger, more productive and more drought resistant and quickly became the only seeds farmers used by 1935. This was particularly important during the dust bowl period from 1934-36.

This corn was more productive and eventually required more nitrogen and thus the use of more fertilizers. And following World War II, nitrogen fertilizers became much more inexpensive and available. The great increase in productivity in corn farming was thus a combination of these more productive hybrids and the fertilizers farmers applied.

So, to conclude, your grandfather probably used pesticides and fertilizers just as we do today. However, the pesticides we use now are certainly safer and used in lower quantities. And, as Bruce Ames pointed out in his classic paper, 99% of the pesticides we find on plants were made by the plant itself for self-protection, and the amount of actual man-made pesticides is way too small to be of any significance.

Like Thomas Wolff said, You Can’t Go Home Again. Farming has changed because of larger farms which attract more insects, foreign insects without natural enemies, and more productive hybrid cash crops that require more inputs such as fertilizers.

References

  1. Frederick Fishel, “Pest Management and Perspectives,” University of Florida IFAS Extension, Publication #P1219, bit.ly/1lUvCRs
  2. Bernard Dixon, “Pushing Bordeaux Mixture,” The Lancet Infectious Diseases, 4(9) 594, 2004. bit.ly/1dv3hfn
  3. James E McWilliams, “Let us Spray: the transition to manufactured insecticides,” bit.ly/1roWQDx
  4. USDA. Farmer’s Cyclopedia, Plant diseases, prevention and Control. 1919, bit.ly/1jwQD30
  5. Wessel’s Living History Farm, “Early Pesticides; 1930s,” bit.ly/NKH5H8
  6. Wessel’s Living History Farm, “The Dawning of the Chemical Age of Pesticides: 1940s,” http://bit.ly/1m65ZNF
  7. S. Savage, “Why you probably don’t know that pesticides have changed,” Applied Mythology blog, bit.ly/1iA7vqg
  8. James Crow, “90 Years ago: the beginning of hybrid maize,” Genetic Society of America, bit.ly/1p5RgnI
  9. Bruce Ames, et. al., “Dietary Pesticides are 99.9% natural,” Proc Natl Acad . Sci, 87, 7771-7781, 1990. bit.ly/1jboGAN
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