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Congress Wants to Destroy Drug Crops with Fungi: A Q+A with Mycology Expert John Taylor

Back in December "I came across a 186-page government-ordered report": that reviewed the scientific feasibility of using fungi as a targeted...

by Derek Mead
Feb 15 2012, 5:00pm

Back in December I came across a 186-page government-ordered report that reviewed the scientific feasibility of using fungi as a targeted killer of drug-producing crops. On the surface, it’s a fascinating, if not frightening, idea: Rather than fight the Drug War on the street, the U.S. government could release tons of fungal spores that specifically kill drug crops.

Think about it from a political perspective: With our government talking a big game about austerity, destroying drugs at the source would likely be cheaper than enforcing laws dealer-by-dealer. Of course, there are two less idyllic scenarios: Either the selected fungus works extremely well, and just wrecks plant and animal life (as has happened on numerous occasions in the U.S., although they weren’t planned applications), or, more likely, it turns out to be extremely costly and ineffective.

To get the straight dope from a specialist, I talked to Dr. John Taylor, a professor of mycology at UC Berkeley and one of the 14 members of the committee that conducted the review. We chatted at length about the potential for a fungal drug apocalypse. After he noted that his opinions are his, and not of the committee’s, we also discussed whether or not dumping plant-killing fungal spores into a foreign country is actually a good idea.

So where did this idea come from, to be using fungi to target specific crops?

Well, in the 1970s biocontrol was a big deal. There was a lot of research done. Some of the best examples are insect parasitoids that target pest insects. People worked on those and thought "Gee, fungi attack plants, maybe we can get fungi that will serve as herbicides."

You know, when I think about someone in Congress hearing about this it’s like "Hey, we can spray some fungus and it will kill all the drugs. Problem solved." What did the committee find?

Well it all depends on who reads the report, right? As you know, two people can read the same article, and they pick out the parts that support their bias, if they’re biased to begin with. First of all, the committee was told: You just deal with science, you're not dealing with policy. That was our mandate, and I think anyone who reads the report will see two problems with using fungi as mycoherbicides in this context.

The first is that there has not been a lot of successful use of fungi to serve as herbicides. Where it's been successful, the targeted plant is non-native and the fungus hasn’t evolved in the presence of that plant.

I believe the US government approached the governments of the Andean countries at some point with the proposal. What country would like another country spraying fungus over them?

The problem in this study is that the fungi they picked to look at are fungi that naturally attack the drug crop. Those plants have had time to develop defenses against the fungi. In this situation, you will just encourage the success of resistant plants. That's the first problem. Just with that, the program is not likely to be particularly effective.

The second problem is that mycoherbicides have only been successful when testers have had the cooperation of farmers, who actually want to get rid of the weeds. In the case of drug crops, you will not have that cooperation. In fact, you'll have farmers who are actively trying to discourage the use of mycoherbicides, potentially by breeding for resistant plants, and that's going to make the application even more difficult.

Then the other concern is a big unknown. You don't know what other plants might be attacked when you increase the amount of a particular fungus in an area.

What kind of environments are you targeting here? How does that come into play? Because when I think about the cocaine trade and opium, those are vastly different environments.

Well, yeah, they are vastly different environments, and the method of applying the fungus and all the other details that would need to be worked out would certainly be different for the two areas. In Afghanistan at one point, researchers made some calculations on just how much water it would take to make enough spores to effectively attack opium crops. It wasn’t clear if there was enough water in Afghanistan to do it. So there would be huge practical concerns.

It's possible to use fungi as herbicides on drug crops – you can never say something is impossible – but the cost of doing it looked to us to be prohibitive. Apart from the fact that it was likely not to work very well, just the cost of researching every possible angle would require a tremendous amount of money, a lot more than the report itself cost.

Yeah, that was another point that the report hit on, was that there hasn't been much testing of this, and I wasn't sure if that's because of funding, or if it's hard to get approval, to say, you know, "Let's test some killer fungi!"

Well, I'm not an expert on testing killer fungi, but I'm guessing it would be hard. As I understand it, there are acts of Congress that mandate any such testing would have to take place in the United States. We've got a lot of safeguards for our environment and for introducing pathogenic fungi that have not evolved here onto crops that did not evolve here. Those concerns are likely to engender a lot of citizen concern.

That part really stood out to me. We already have an idea that it might work, but we don't know how well, and to test it we'd have to test it at home, basically.

That's my understanding, but you know, again, we were admonished not to consider the social aspects. We really did not get deeply into that area. But it's worth remembering that the first work on this, the work I told you about by Art McCain, was aimed against cannabis (PDF). That mycoherbicide would have been used in the United States. You know, if you just think about the social forces that would be in play… that's a big barrier to this approach.

Definitely. From what you understand of how this works, you couldn't just fly over Columbia and spray out spores like you would chemical herbicides, could you?

Well I believe the US government approached the governments of the Andean countries at some point with the proposal to do just that, and I believe they replied "No, we really wouldn't like you to do that." What country would like another country spraying fungus over them?

But if you wanted to use Fusarium on domestic cannabis, you'd have to think: How would this play in California, if federal planes started spraying a fungus over Mendocino County?

I can’t imagine any that would.

I believe Clinton, when faced with an opportunity to do just that, decided that that was not a good idea. It could easily be construed as something like biological warfare. I think the social aspects deserve their own study. The evidence suggests that no government so far has been very excited about having another one spray microbes over its country.

Yeah, I think that is a hard thing to sell.

That thinking might be why governments don't want to invest a ton of money in [mycoherbicides]. They don't see it going anywhere.

So, if you got rid of the political barriers and you were to do this, if you were to find a fungus that was particularly effective, what are the end risks of actually utilizing this?

Until you do the research you don't know. I would say the risks would depend on how carefully you did the research before you released the fungus. I mean, we're talking about a big project and a lot of time, to test your fungus on the plants in the area that might be affected by it.

I also think you can't ignore the social problem. At all levels. For example, if you're an Afghani opium farmer, there are things you can do to prevent the application of fungi. You could shoot the airplanes. There would likely be some resistant cultivars, and the farmers could start propagating them.

Using this approach, using mycoherbicides in a hostile environment and biologically in the worst situation for actually controlling the plant, you'd be starting out with a lot of marks against you.

And, as you pointed out, mycoherbicides have not exactly taken off as the herbicide of choice around the globe. They have been very useful in a few situations, and it's something to consider, but the situation given to the committee was not ideal. In fact, it's probably one of the worst ways to try to use them.

It'd be a lot easier to attack cannabis in the United States, where it's not a native plant. And if you could do it with a fungus already native to the U.S., that would easier still. Using a fungus native to Afghanistan on a plant native to Afghanistan is going to be tougher.

Interesting. This would be more effective against cannabis?

I’m not sure. The Fusarium that McCain worked with was isolated from hemp plants in Italy and the natural range of cannabis is South and Central Asia, so the fungus may or may not have come from cannabis's natural range. My guess is that if you were a cannabis farmer you could probably get around it by finding resistant strains.

But if you wanted to use Fusarium on domestic cannabis, you'd have to think: How would this play in California, if federal planes started spraying a fungus over Mendocino County? People would not be happy.

Where fungi are causing problems – and they do without any group trying to create a bad one – is where they're moved from continent to continent. That movement happens all the time.

Thinking about the history of attempts to use biological controls, a lot of them haven't gone very well. What are the odds that this ends up being a fungal apocalypse that just kills all the plant life on Earth or something like that?

No, there wouldn't be a fungal apocalypse. First, if the people making decisions read the report, they wouldn't go that way. The report comes down pretty strongly on all the problems that we face. If they read the report, they would be dissuaded from investing in that line.

If you, for example, put a lot of the mycoherbicide fungus Crevellia in Afghanistan – as much as you could make – it might not have much effect, because there's already a lot of that fungus there. And although you could make truckloads of it, when you think about how many spores are already produced in nature, you might not be adding that much. The plants that are susceptible might suffer a little bit more, but the plants that have resistance to the fungus, that have evolved that resistance over the ages, might not be affected. The use proposed for example in Afghanistan is probably a good scenario for not causing additional environmental problems, but it's a bad scenario for actually achieving control of the drug crop.

There are 100,000 described fungi in the world, and estimates range from 1 ½ million up to ten times that number of actual fungal species in nature. There are a lot of fungi out there, and many of them earn their living as parasites of animals and plants. But animals and plants are evolving all the time to counter that parasitism.

So if you wanted to make a super fungus that would kill all the plants on Earth, well… good luck with that. That would be a case where I'd be willing to use the word, impossible.

An exotic (non-native) fungus is wreaking havoc on bat populations in the U.S.

Where fungi are causing problems – and they do without any group trying to create a bad one – is where they're moved from continent to continent and brought to an area with hosts that are naïve with respect to that fungus, hosts that didn't evolve with that fungus. That movement happens all the time.

In a few of those cases the fungus finds a host that's ideal, and the fungus can nearly exterminate that host. A classic example from the United States, from the early part of the 20th century, was a fungus brought in that killed the chestnut trees. It killed off 4 billion trees. It's still around, and chestnut trees are still around, but they can't get big enough to reproduce before the fungus kills them.

There used to be elm trees all over the United States, and a fungus came and pretty much wiped them out. There's an oak relative, tan oak, that is being wiped out by a fungus. The disease is called Sudden Oak Death. The Monterey Pine tree is on it's way out, due to another fungus, another Fusarium species.

These disasters had nothing to do with government projects to make a fungus, or with bioterrorism. The buzzword we use is that they are bio-errors. They're due to the transport of living plants that carry with fungi them. There's a huge trade in plants, and people in that trade of course are not interested in any additional regulations, so there's no reason to think that that problem is going to quietly go away.

On the animal side, the most tragic one is a fungus that spread around the world and is killing amphibians. It's a global demise of amphibians, I think nearly a third of the species of amphibians are affected. Its area of origin is probably Africa, although that's not completely certain yet.

Then the more recent one is the white nose syndrome of bats that appears – again, it's not certain – but looks like a fungus that came from Europe. It might have been spread by people who explore caves, spelunkers. It started in the Northeast United States and is spreading south and west, killing as much as 90% of the populations of half a dozen species of native bats.

I think I understand where people are coming from when they say "Let’s use fungus to control something else." But in this case, the outcome is either random, or simply not feasible.

Yeah, I think it's too hard to do. To say I'm going to exterminate this plant with this fungus is very hard. To say I'm going to exterminate a plant with a fungus is easier. But you don't know which plant. If I were the powers that be, and had a lot of government money, I would put that money into trying to prevent the intercontinental spread of plant pathogens that hitch rides on plants or plant products, not into trying to make a mycoherbicide against drug crops. The economic effects of the unintended spread of pathogens are huge, and the problem is so big you can't do anything about it afterward. The only possible action is to prevent it in the first place.

Yeah, well I think that hits the nail on the head right there. I had one last question for you: I was wondering if you had any good fungi jokes that you tell in the trade?

Oh god, no, they're all really lame. The classic one is "you’re a fun guy" but… no.


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