Bad Plants Go Good

Bad Plants Go Good

Part of Ep. 1303 Plant Communities

UW-Extension Plant Pathologist Brian Hudelson looks at some other plant diseases that are beneficial to people.

Premiere date: Oct 05, 2005

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley:
I'm with UW Extension plant pathologist Brian Hudelson. I just learned about corn smut, or Huitlacoche. And it's all your fault!

Brian Hudelson:
I guess so, isn't it.

Shelley:
You were the one that suggested corn smut. For some reason, plant pathologists seem to get a lot more excited about diseases than the general public.

Brian:
Yes, I think that is generally true.

Shelley:
Corn smut was interesting because it was a disease that was a benefit to us. Is that an isolated case?

Brian:
Most of the time, when plants are diseased that's not a good thing.

Shelley:
Only for you.

Brian:
Only for me, yeah. But there are examples, other than corn smut where the diseases are actually a benefit to humans. I'm holding an example of one right here. This is a disease called ergot, which is common on grasses, including some of the more common small grains like wheat, rye and barley. It's a fungal infection, just like corn smut. The individual grains in the seed heads get infected. They swell up and turn this blackish-purple color.

Shelley:
Again, just like the kernels of the corn.

Brian:
Right, and in this particular case this fungus happens to produce a variety of different types of very toxic compounds. And if you're feeding this sort of grain to cattle or if humans eat too much of this you can end up killing the animals or the humans. This particular disease has a huge history.

Shelley:
It's been around a long time.

Brian:
Way back to the Middle Ages. There was a problem called St. Anthony's Fire, which was caused by ergot. People would grow grain and it would have ergot. They would harvest the grain and then grind up the grain, make flour and bake bread. Unfortunately, these toxins aren't destroyed by the heating process. Then, folks would eat the bread and they would come down with a variety of different symptoms, sometimes circulatory problems that would lead to gangrene. If you eat enough of this, you can kill someone off with this particular disease. There was a group of monks in Europe the Order of St. Anthony. They set up hospitals to treat folks suffering from ergotism, as the disease was called.

Shelley:
Isn't ergotism generally blamed now for what resulted in the Salem Witch Trials?

Brian:
Certainly, there are some people who theorize that the women who were accusing folks of being witches had eaten the bread that had ergot in it and were hallucinating, another symptom of the disease. And maybe were actually imagining that people were flying like witches.

Shelley:
Maybe they thought they were really flying.

Brian:
Right. But what's interesting about that particular disease, is now folks actually inoculate grain fields with ergot. Because folks found that if you isolate some of these toxic compounds out of the grain you can use them in very small dosages, for example, to induce labor in pregnant women. And also, to sometimes treat migraine headaches.

Shelley:
So, it has a good side.

Brian:
That's right, even though it's a very nasty disease in many ways, it can be beneficial to us.

Shelley:
So, if I see it in my backyard, don't eat it but let the scientists work with it. Okay, I'll behave. Here's another one that I have seen in my backyard. Generally, when I get beans like this, I throw them out.

Brian:
This is a disease called bacterial brownspot. It's caused by a common bacteria. Most plants have this particular bacteria on their surfaces. Oftentimes, there's no disease at all. But when you get high enough populations of the bacteria, you get brown spots on your beans. You can also get a disease on your lilacs called bacterial blight. This is a really interesting organism. There were some researchers here at the UW who were grinding up corn leaves to inoculate their corn fields. And they inoculated half the field with this ground up leaf material and left the other half non-inoculated. That evening, there was a frost. When they came back the next morning the half of the field that had been sprayed with this ground up corn material was frozen. And the other half was not. They eventually found out that this particular bacterium can actually induce frost formation. There's a little protein in its cell membrane that mimics an ice crystal.

Shelley:
What good is that?

Brian:
Well, what they found was they can take this protein and they can use it to make snow at ski resorts.

Shelley:
There's a reason for the skiers to eat their green beans! That's where they're getting their snow. How neat is that! What else?

Brian:
I have a poinsettia here, which is a very common Christmas plant. It's not red yet, unfortunately, in this particular example. But in this particular case we have an infection of an organism called a phytoplasma. This is a bacterium-like organism living in the food-conducting tissue of the plant.

Shelley:
It's pulling it up? It looks healthy, though.

Brian:
It looks very, very healthy to us but actually, it's most likely diseased. They found that a lot of poinsettias are infected with this particular organism. And phytoplasmas, in general, tend to cause stunting and also oftentimes induce branching in plants.

Shelley:
Not very good in my backyard.

Brian:
Not necessarily, but in poinsettias that's a good thing, because poinsettias often grow very large, tree size. And phytoplasms will keep them short.

Shelley:
So they can be in my house as a house plant.

Brian:
That's right. Interesting.

Shelley:
Another bad thing turned good for us.

Brian:
That's right.
Shelley:
There's one last one that's been around forever. I've always loved the history of it. It's tied in with tulips in the 1600s.

Brian:
That's right. There's a group of tulips called the Rembrandt tulips because they were grown back in the time of Rembrandt. And a lot of Dutch artists actually painted these tulips.

Shelley:
They were pretty!

Brian:
They're beautiful, striped petals, fringed petals, very, very attractive. As it turns out, these particular plants were infected with a virus called the tulip breaking virus. That virus caused the striped pattern in the petals.

Shelley:
Of course, nobody knew that back then.

Brian:
Nobody knew that at the time. They were quite valuable. There were people who were selling homes and boats to buy single bulbs of these.

Shelley:
Can you imagine?

Brian:
Unfortunately, virus-infected tulips tend to decline very rapidly. They don't last very long.

Shelley:
They didn't get a real good deal?

Brian:
That's right. Now, striped tulips are at our garden centers. These are not virus infected, typically, but they've been bred for that particular stripe characteristic and blossoms.

Shelley:
Probably inspired by those viruses back then.

Brian:
These particular bred tulips actually last a lot longer.

Shelley:
Well, maybe not still worth a boat.

Brian:
Probably not.

Shelley:
I can't wait to see what's next in the plant disease world.

Brian:
I think we'll discover other things that are beneficial.

Shelley:
Great, thank you, Brian.

Brian:
You're welcome.

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