The Drug War's Fungal
"Solution" in Latin America
page 1 page 2
page 3 page 4 page
5 page
6
Printable version: HTML Word RTF WP
"Andean Seminar" Lecture Series
sponsored by GWU and WOLA
Friday, December 8
Jeremy Bigwood
This afternoon I will speak of the recent history of "biochemical" or "biological" agents called "mycoherbicides’, fungi that have been designed to infect and kill drug plants, such as coca, poppy, and marijuana, with a special emphasis on the proposed use of mycoherbicides in Colombia and their possible clandestine use in Peru during the 1980s until the present.
I prefer to characterize the activities of mycoherbicides as "biochemical" rather than "biological," because in all cases, mycoherbicides attack their targets, or even non-target organisms – plant or animal– through the synthesis and secretion of fungal toxins, called "mycotoxins". These compounds, to which the fungus itself has immunity, are synthesized and secreted to dissolve the cell walls of the target species after which the cell's contents can be absorbed into the cells of the attacking fungal cells. The fungus then reproduces itself and moves into the physical space of the target cell and starts the process over again until it is itself killed or it has killed the host. Where no food source is present, it can remain dormant for years. To summarize, mycoherbicides are fungi -living biological organisms that gain access to the cells of target species through secreted toxic chemicals.
In order to provide context, at this point it would be useful to take a quick comparative look at the methods used to eradicate drug crops.
The first method is manual. In this method, plants are removed by destroying them physically, for instance, pulling them up by the roots. This technique has been successfully used in the US, and by US-funded para-police, para-military forces that I consider to be mercenary, such as UMOPAR and CORAH in Bolivia and Peru respectively. Even though the actors may disgust us by having sold themselves to a foreign power with an aim to damaging the well-being of their compatriots, the manual eradication they perform causes the least amount of environmental harm, but exposes the eradicator to the hostility of local farmers.
The second method is chemical. A chemical is mass-produced in a laboratory, mixed in a formulation with other additives, and applied to the target often by air. Below is a brief series of herbicides used by the US government, starting with the mixture that was called "Agent Orange" and used in Vietnam, and ending with the present-day favorite, Glyphosate - which with other additives is being used today to defoliate wide swathes of the Amazon in Southern Colombia.
All of these chemical herbicides have known toxicity, ranging from the mutagenic and carcinogenic breakdown products of Agent Orange, to the effects of Glyphosate on aquatic life and soil microorganisms, not to mention the collateral damage caused to nontarget plants and animals by drift.
Below, are the major Fusarium mycotoxins, the active ingredients of the Fusarium species and the primary subject of today's lecture.
The concept behind the use of these organisms is that their spores are to be mass-produced in laboratories; these are then applied over the target species, where the spores germinate, spreading toxic mycelium that will attack the targets. The concept, according to the proponents of mycoherbicides, is that these fungi are specific and will only attack the targets they are designed for, a concept that has not been supported by the scientific evidence. Also, allow me to emphasize that while mycoherbicides are organisms, living entities, their activity against their targets is mainly chemical - produced through the chemicals they synthesize, and they do not attack through mechanical means. Above are illustrated the major classes of mycotoxins found in Fusarium.
What do we know about mycotoxins in general?
Most, if not all fungi produce mycotoxins. These chemicals may be part of a defense mechanism for the organism or may be offensive, or both. Some well-known mycotoxins that have both deleterious and positive effects are from ergot, a fungus that can inhabit rye, whose infestations and contamination of bread have led to the poisoning called "St. Anthony’s Fire," in which large groups of intoxicated people have died, after experiencing hallucinosis, and loss of feeling in the extremities. This was a particular problem during the middle ages and was solved by separating the purple-black fungal sclerotia from cereal. In fairness to ergot, I should point out that in the modern age, mycotoxins isolated from ergot have a wide range of medical uses: ergotamine alleviates migraine headaches, and ergonovine has saved the lives of countless women who have taken it to control post-partum hemorrhage. So far, there are no such positive uses of Fusarium mycotoxins.
Another thing we know about mycotoxins in general is that their production by fungi is very dependent on environmental circumstances and available nutrient sources. Thus, it is often possible to take a fungal strain that is known to produce high amounts of a given mycotoxin, cultivate it on a given media, and find no detectable mycotoxins. The opposite is also true. Some fungi that produce small amounts of mycotoxins in the wild can be induced to produce larger amounts -or even different mycotoxins in the controlled conditions of a lab. This caveat becomes important when trying to wade through the mycotoxicological literature in which at certain times a given species isolated by certain scientists have been found to contain compound X, but other scientists have only found compound W, Y, and Z! As is often the case in academic minutiae, and especially in the world of mycology, these debates can rage for decades until one side or the other dies off.
Fusarium mycotoxins:
What do we know about Fusarium mycotoxins? So far, Fusarium mycotoxins have had an entirely negative history. So negative, in fact, that when I was working with mycotoxins in the 1970s and early 1980s, I was permitted to work under DEA license with psilocybin, ergot alkaloids, and without any license for the very toxic Amanita toxins, the GABA-mimicking mycotoxins, but I was not permitted to work with the Fusarium toxins. Why not? These Fusarium toxins were considered to be weapons of war!
And what do we know of Fusarium as a genus? The first written description of a Fusarium rot of corn comes from a Spanish friar in Mexico during the 1600's. The botanist Link first described the genus in 1809. Fusarium became associated with the rot of stored potatoes by German scientists in the 1850s. However, this should not to be confused with another rot of living tubers caused by yet another species of fungus, Phytopthera, the fungus that caused the great Irish potato famine during the 1840s.
In the 1890s, horses, cows, and pigs were reported as losing hair and hooves after eating Fusarium-infected grain in Nebraska. This was the first report of the toxicity of the species. Various species of Fusaria were then shown to attack many crops, including cotton, banana, sugar cane, and cereals, and even humans.
Also, in this timeframe, in 1916, the first report of Fusarium infection (Fusariosis) in humans was published in an Argentine medical publication, in which a patient suffered from Fusariosis of the nose!
