- [Instructor] Let's imagine your corn farmer
and you would dream of having nice, healthy corn crop,
like we see in this picture.
But being a farmer isn't as simple as planting the seeds
and making sure that the crop gets enough sunshine
and water and fertilizer, you also have to deal with pests.
And pests you can view as anything
that might eat your crop or destroy your crop,
or make it just really hard for you to have a good crop.
Now, some of you all are familiar
with the notion of pesticides,
where you're essentially poisoning the pests.
Now for various reasons, that might not be a good idea,
and we'll talk more about it.
And so there's a notion of integrated pest management,
which is how we can do multiple things which might include
pesticides or might not include pesticides, to really keep
things under control.
And to get a good sense of how bad a pest can be,
I will introduce you to the Western corn rootworm.
Now, the reason why it's called a worm,
even though in its adult phase,
it does not look like a worm, is that in its larval phase,
when it's a baby, it looks like a worm.
And even though the adult will also feed on the corn silks,
the real damage is done in the larval stage.
When they're feeding on the roots,
that's why they're called corn rootworms.
And the USDA estimates that just in the United States,
damage due to Western corn rootworm is about
$1 billion per year.
About 800 million of that, is just lost corn crop.
And about 200 million of that is all the costs in order
to prevent this pest from doing their damage.
Now, as I mentioned, if we think about
integrated pest management,
there's many ways of addressing this.
One way of course, that many people think of, is pesticides.
And this is an image of crop dusting.
I don't think this is a corn field here,
we can see the pesticides coming from the biplane.
And it's a way of spreading the pesticides,
not the only way, but for various reasons,
this is not optimal.
You could view it as polluting the environment
in certain ways.
A lot of us aren't so keen on eating crops
that have pesticides on them.
And we've learned in other videos on evolution and natural
selection, there's variation in any population.
And the more that you expose a population to something,
and it kills off the ones that are susceptible,
the more chances that the ones that aren't as susceptible,
reproduce and thrive.
So at some point you might have an insecticide resistant
pest on your hands and then your insecticide,
isn't going to be all that useful.
So when we think about integrated pest management,
we think about art,
what are other ways to address this?
Maybe in conjunction, maybe ways
that could be perceived to be more natural?
Well one obvious thing is to think about, well,
what are the predators of that pest?
And this is the wasp spider,
and this is what's known as a ladybug in North America
and ladybird in much of the rest of the world.
And they will actually feed on the Western corn rootworm.
So you might want to introduce this onto your farm
if you're trying to grow that corn.
Another thing that farmers have done
to some degree of success, is early planting.
By planting the crop early,
it's less favorable for the root worm to lay their eggs.
And also it gives a chance for the roots to get stronger,
so that by the time that they're attacked by the rootworm,
they're going to be more resilient.
You could also have hybrid versions of corn
that just have larger roots.
So once again, they're going to be more
resilient to the rootworm.
Another technique is to genetically modify the corn.
And that also is a bit of a controversial topic,
depending on who you talk to.
You might've heard things about GMO,
genetically modified organism.
Some people think they're fine.
Some people are wary of them.
But there is a transgenic version of corn.
Transgenic means, that we took DNA from some other organism
and put it into the corn.
And that transgenic version is known as BT corn.
That actually has DNA from a bacteria,
which produces a protein,
which is harmful to certain types of root worms.
Now, another really interesting technique,
which people have used to some degree of success,
is known as crop rotation.
Let's imagine looking down from the sky
onto a corn crop here.
So we're looking down from above.
So what normally happens is,
is that the eggs are laid near the corn
and the larvae can't travel so far.
So they, if they're near the corn,
they get to the roots and then they're able to,
the reproduction cycle goes on.
But if we rotate the crops so that the next year we're not
planting here, but maybe we are planting the corn over here
and then in that first place, we're planting soybean.
Well, that can solve the problem,
because the eggs will be laid here.
But next year the corn is going to be here.
And over here, we will have the soybean,
which is not a suitable food for the corn rootworm.
Now what's really interesting,
and this is another one of those fascinating stories
of evolution and natural selection,
are there cases because there's variation in populations,
where some of the adult rootworm actually doesn't lay their
eggs in the same corn crop, where they feed,
they lay it in an adjacent corn crop.
So that next year when the crop rotation happens,
then their larva are going to have access to the corn
in the other field.
Now you might say, how did they know that?
How did they know that the farmers were planning to rotate?
Well, generally the rotations are pretty simple.
You keep alternating between two crops
like corn and soybean.
And most of the Western corn rootworm
would not have done that,
but just some of them might have started to randomly travel
a little bit further.
And then those would be more likely to reproduce.
So the ones are more likely to reproduce
will then exist more.
And then that behavior would be passed on,
if it is a genetic trait.
There's other situations once again,
because of the variation in populations,
where some of the eggs stay dormant for an extra year.
So even though you might rotate to corn this year,
the year after that, you rotate back to corn
and then the eggs hatch and the larva can feed.
So it's a fascinating, almost arms race,
between the farmer and these pests.
But I hope you appreciate, it's far more interesting
than you might have realized before.
And I haven't even given you a comprehensive list
of all the types of pests and all of the ways
that you might want to manage it.
You can do physical removal, you could do barriers.
Maybe you'll think of another creative way
to have integrated pest management.