This is the second in a series of posts that seeks to explain some of the detailed, crop-specific reasons that pesticides get used, and how that is actually important for true agricultural sustainability. In this post I’ll talk about a pesticide that is a main-stay of Organic farming and also widely used by other farmers.
Fire and Brimstone!
“Fire and Brimstone” is a biblical expression describing Hell that later became a derisive term for a style of Christian preaching. The term “brimstone” is the ancient name for the highly irritating element, sulfur, and it was a vivid image of why you wouldn’t want to end up in Hell!
It turns out that “brimstone” (sulfur), is not just a Biblical image of eternal suffering, it is an important and widely used pesticide active against certain diseases and against mites.
Sulfur is exceptional in many ways:
- It is the oldest of all pesticides (~5000 years, to early Egyptian civilization)
- It is still the most heavily used pesticide in California (if represents 26% of the pounds of the top 100 materials used in CA – over 40 million pounds in 2008)
- While modern pesticides are used in the range of a pound to a few ounces/acre, sulfur is used at 4-10 lbs/acre and as frequently as every seven days
- It is the pesticide that leads to the most farm worker complaints (skin, eye and lung irritation )
- This pesticide has been predicted by a new risk model to cause significant “bird kill” at the rates at which it is commonly used – particularly on grapes (table, wine, raisin)
- It is by far the most widely used fungicide/miticide in “Organic” agriculture
OK, now I’m going to argue that sulfur (brimstone) is actually an important part of agricultural sustainability.
Considering the above information, you should probably be asking, “why in the ‘place with brimstone’ would you defend the ‘pesticide from hell?!’”
This is not an academic argument. Right now, I’m actually involved in a “broad stakeholder” process that is trying to define what sort of pesticide use is “sustainable,” and I find myself in the very unlikely position of defending sulfur. For instance, I am arguing that the model which says it kills birds needs to be validated before we can reach that conclusion.
I’m not really a likely candidate for this job of defending sulfur. I’ve spent enough time doing experimental work in sulfured vineyards to understand how irritating it can be. My consulting clients are not the companies that sell sulfur, they are the companies that invent newer, better alternatives. So, why would I defend sulfur?
A Walk in a Vineyard Without Sulfur (c 1980)
I remember being in an experimental vineyard plot around bloom in early June, probably around 1980. I was shocked to smell a pleasant fragrance - nothing like the acrid smell of sulfur that I had come to associate with any vineyard. This was an experimental block that had only been treated with the new, synthetic, DMI fungicide, Bayleton. It was the first real alternative to sulfur that the grape industry had ever seen. Grape flowers don’t even have any petals, they don’t need to attract pollinators, but with no sulfur around you could smell the wonderful fragrance that they produced (perhaps as some sort of evolutionary remnant? )
The Development of Pesticide Resistance
Well, that scent (whatever it represented) might have been noticed in a lot of California vineyards in the early 1980s as growers happily moved away from weekly sulfur dustings to applying Bayleton every three weeks. But quickly, the grape powdery mildew pathogen developed resistance because of the over-use of Bayleton. Because of that, Bayleton is no longer a viable tool for disease control for California grape growers.
Why Sulfur Is Still Important Today
Today, the grape industry has several other good alternatives to sulfur for powdery mildew control, but it still uses sulfur as a part of the seasonal control program. The sulfur serves to reduce cost, but most importantly, it serves to prevent resistance development as happened with Bayleton. So it turns out that the ‘pesticide from Hell’ is an important reason why the more benign options can be used in a sustainable fashion.
There are lots of other examples like this in other crops where relatively old, high use-rate products are still used because they help prevent the development of pest resistance to the newer alternatives. These chemicals don’t quite rise to the standard of ‘pesticide from hell’ but they are other examples of less-than-ideal options that serve to preserve the usefulness of much “softer” compounds. (I should also point out that sulfur is an important plant nutrient and is in some essential amino acids we require in our diet – it is just an issue of quantities).
Organic grape growers are pretty much limited to sulfur because even though the new synthetic fungicide options are safer, they do not fit under the “natural” limitation. By the way, some Organic growers in various crops use flame weeders for weed control, in which case they round out the entire ‘Fire and Brimstone’ image.
My next post in this series will be about “Pesticides that buy time.”
Air applied sulfur image from NARA/EPA, 1972 in the National Archives. Typically, sulfur dust would be applied with ground equipment.
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