Written by Steve Savage
Amy Harmon’s excellent article in the New York Times describes how the Florida orange juice industry may soon be wiped out because of a new bacterial disease spread by an introduced insect. There could be a technology fix for the problem using genetic engineering, but the question is whether the growers will get to apply that solution.
The sort of crisis situation now facing the Florida orange industry is not at all unique in the history of farming. There have been many times when some new pest threatened the economic viability of a major crop.
Sometimes the pest “wins” and a particular farming industry simply goes away. In the mid 1880s when Coffee Rust made it from Africa to the coffee plantations that supplied England from Java and Sri Lanka, the industry collapsed, and so the English had to switch to tea to get their caffeine.
When Wheat Stem Rust made it too hard to grow wheat in the Southern colonies of what would later become the US, the farmers shifted their cropping to cotton and tobacco. That involved much higher labor requirements which in turn lead to the sad institution of slavery in that region.
But there have been other times when some new technological breakthrough has saved a threatened crop, as it possibly could for the Florida orange growers. I’ll give just one example here.
Back in 1874, a plant scientist name Pierre Millardet was walking down a road in Bordeaux France. The famous vineyards he was passing were being devastated by a fungal disease called downy mildew. It had been unwittingly brought across the Atlantic by the British who came back with specimens of the wild grape species they found in North America (e.g. Vitis labrusca – Concord types). Those grapes harbored the downy mildew which was not too problematic for them, but the Vitis vinifera grapes of the Old World were extremely susceptible. The wet climate of Europe was also ideal for fostering the fungal epidemic.
Millardet was very concerned about this problem as were all the French, looking at the possibility of not being able to produce wine. As he walked past vineyard after vineyard nearly defoliated by the disease, he came upon one small part of a vineyard that looked remarkably healthy. He quickly sought out the owner to ask why those vines looked so good. It turned out that the grape grower had been frustrated by the fact that so many passers by on the road would help themselves to his grapes as they ripened. He had concocted a mixture of copper sulfate and hydrated lime and sprayed it on the grapes to make them less attractive.
By accident the farmer had developed an effective fungicide. Millardet promoted this option, and soon the “Bordeaux mix” saved the French and other European grape industries. It also saved the European potato crop which was also being devastated by a related disease that belatedly followed the potato from its origins in the Andes and caused the epic Irish Potato Famine.
Fortunately, we have many superior fungicide options to protect these crops today. Copper-based fungicides were “state of the art” in the 1870s, but they are rather toxic to mammals, persistent in the environment, and bad for aquatic invertebrates. One of their remaining uses is in organic farming which has only a few fungicide options that qualify as “natural.” New, synthetic fungicides that protect grapes, potatoes, wheat and other crops in Europe and elsewhere are far better for health and the environment. Still, without the accidental discovery of the “Bordeaux Mix,” the European wine grape industry could have disappeared.
I gave an invited talk for the Specialty Coffee Association and its annual symposium back in February. The Arabica coffee growers in the highlands of Central and South America are facing a severe, new threat from a disease called coffee rust. My role at the the conference was to put that crop threat into a global and historical perspective. This grape disease story is one of the examples in my talk titled: “Humans vs Pests, The Long View.”
Written by Guest Expert
Steve Savage has worked with various aspects of agricultural technology for more than 35 years. He has a PhD in plant pathology and his varied career included Colorado State University, DuPont, and the bio-control start-up, Mycogen. He is an independent consultant working with a wide variety of clients on topics including biological control, biotechnology, crop protection chemicals, and more. Steve writes and speaks on food and agriculture topics (Applied Mythology blog) and does a bi-weekly podcast called POPAgriculture for the CropLife Foundation.
My roses have black spot – I wonder how related that fungus is to things like coffee rust or downy mildew. I bought some copper sulfate (it’s organic!?) but it doesn’t seem to be working. I hope I have better luck with a modern fungicide.
Black spot is from a different class – Ascomycotina (vs Basidiomycotina for rust or Oomycetes for downy mildew). Copper sulfate would have to be applied very frequently to be effective. Some of the better options are available to homeowners now. Look for the systemic actives like Tebuconazole or Propiconazole or Myclobutanil. Those are >20 years old, but they are the newest options sold to the public. They are far safer than copper sulfate for us or for the environment.
Thanks very much! I’ll have to see if those are available at my local Home Depot.
was wondering if you have sources on this:
“Fortunately, we have many superior fungicide options to protect these crops today. Copper-based fungicides were “state of the art” in the 1870s, but they are rather toxic to mammals, persistent in the environment, and bad for aquatic invertebrates. One of their remaining uses is in organic farming which has only a few fungicide options that qualify as “natural.” New, synthetic fungicides that protect grapes, potatoes, wheat and other crops in Europe and elsewhere are far better for health and the environment. Still, without the accidental discovery of the “Bordeaux Mix,” the European wine grape industry could have disappeared.”
Is copper still used in organic farming? I’ve read mostly no but was curious to see some info. Also is there a good compiled list of what pesticides are allowed to be used in “organic” farming and what their toxicity effects are compared to their synthetic counterparts.
I think a really good blog post could be written illuminating some of the more harmful pesticides that things like roundup and current synthetic pesticides replaced, as well as GMO crops that require less pesticide use like say blight resistant crops.
There are many different copper based fungicides. Copper sulfate (most like Bordeaux mixture) is fairly toxic (Oral ALD50 330mg/kg http://www.cdms.net/LDat/mp50R010.pdf). Others like Copper Hydroxide are less so ( 1650 mg/kg http://www.cdms.net/LDat/mp135000.pdf). The modern synthetic alternatives are essentially non-toxic to mammals such as fludioxonil for Botrytis (>5000 mg/kg http://www.cdms.net/LDat/mp5EM013.pdf), or Mandipropamid for Downy Mildew (>5000 mg/kg, http://www.syngentacropprotection.com/pdf/msds/03_270461222008.pdf). Copper isn’t something that breaks down into something else, so it is persistent.
Copper is used in much of organic, although some countries in Europe have banned all the uses. I’ve not seen a good compilation of the toxicity and other properties of organic vs conventional products. The fact is that a great many products from both lists are very low in toxicity. The truth is that “harmful pesticides” have been getting increasingly rare. I will be writing about that over the next few months because I’m compiling that history for some talks I’ll be giving later this fall.
Unfortunately, there are not any commercial disease resistant crops except for a couple of examples of virus resistance. Groups in Europe and the US have moved late blight resistance genes from wild potatoes to commercial types, but whether those will ever become available to farmers is unknown. Similarly a bacterial resistance gene has been moved from peppers to tomatoes by 2Blades Foundation. Again, whether it will be commercialized is unclear
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