Hello, my name is Ben Thrash.
I'm a University of Arkansas System Division of Agriculture extension entomologist.
And today we're out here looking at some of our virus plots.
We're evaluating virus on corn earworm
out here in these soybeans, and we're looking at several different viruses.
But what I kind of want to go over today is showing the application timing,
when to apply this virus, looking at size of worms,
how many worms we have out there in the plots, what to look for
post application and what you might expect to see from this virus.
So what you want to remember about this
virus is that it takes a little bit longer to control than our normal insecticides.
Now, a normal insecticide we recommend not going back into the field
until at least three days after application.
Well, with the virus, you know, it takes five to seven days and normally
to see any virus-dead caterpillars.
What you may see prior to that is larvae move into the top of the canopy.
They'll be laid out on the on the tops of the plants,
which normally isn't the case in corn earworm.
But whenever they're infected with the virus, they don't feel very good.
They move to the top of the canopy.
A lot of times what people see is,
they'll go out a few days after application
and they go, 'man I got more worms and what I started out with.'
Well, actually what's happening is you're just picking up
more in your sweep net than you had originally,
because more are moving to the top of the canopy
and they're easier to catch in that sweep net.
So, remember when after an application of the virus, you want to wait
five to seven days before you
before you go out there and evaluate really what you have.
Some things that you want to look for.
Like I said, was moving to the top of the canopy.
The worms can start sweating.
It kind of looks like sweat.
If you get down there really close and look at the worms, you'll see little
almost it looks almost like little water droplets on top of the larvae.
You'll also may start to see some dead and dying caterpillars.
You might start to see some discoloration in some of those caterpillars.
A lot of times they'll start to get lethargic
to where if you prod them with your with your finger,
they don't curl up in the C shape that you're normally used to.
They're just kind of lay there, roll over. If they'll roll over on their side,
they won't upright themselves.
So that's some things to look for five to seven days after application.
So I went through this field
and pulled some leaves that had some dead caterpillars on them.
And you can see just these
kind of greasy spots that are left from some of these old dead and dying caterpillars.
These are just full of virus particles that are just continually spreading
throughout the field to
other newly hatched corn earworms throughout the field.
You know, the thing that I can tell that these are actually dead corn earworm
caterpillars is that you can actually still see the head capsules
left where they are.
And that's pretty much the only thing.
Besides that, you know, it just looks like a greasy spot left out there on the leaf.
So seeing this virus out here in the field, that just allows you to know
that the virus is working and there's more virus out there in the field.
So one thing we get a lot of questions over is storage of the virus.
And people are really concerned about having to store the virus
within a refrigerator constantly. That's not exactly the case.
This virus is pretty stable in the outside environment.
However, you can't store it in the — you can't put it in the back of your truck,
you can't put it inside your truck and leave the windows rolled up.
It's a living organism.
If you do that, you leave it out in the 100 degree heat,
it'll actually kill the virus and render it ineffective.
So that's some things that you need to keep in mind when storing the virus.
If you buy it from the co-op, you can put it you know,
you can put it out at the airstrip as long as it's in the shade.
You can leave it out there for a day, as long as you keep it,
you know, in the shade, keep it in a relatively cool environment,
the virus will be fine.
What you don't want to do,
like I said, is leave it in the truck where it's over 100 degrees in there.
That'll render that virus ineffective.
Some other things we want to make sure that we have in check is our water pH.
You don't want to water pH over 9.
There are some areas in Arkansas where your water pH can be as high as 9.
You want to keep that pH below that, because if it starts getting up near
that, it'll start breaking down that protein matrix that encapsulates the virus
and it will render that virus ineffective.
And you'll be left wondering why the virus isn't working.
So something you have to remember about this virus
is that it only kills corn earworm.
And so it's very important to ID which worms you have
in your field correctly.
And something I always show people is,
you know, it's hard to mix up a large saltmarsh caterpillar with a corn earworm.
But whenever they're first hatched out,
they can actually look quite a bit like a corn earworm.
If you look right here.
That's actually a saltmarsh caterpillar, and this is a corn earworm.
And remember, they're two different colors right there,
but color is not a reliable indicator
of what species of worm that you have out there in the field.
On these little bitty saltmarsh caterpillars,
if you hold them up to the light,
you can actually see those long hairs that are typical
of those saltmarsh caterpillars.
And that will really help you be able to ID.
whether you have corn earworms or not.
You can see there's quite a few other caterpillars out here,
because this virus does not have any activity on those other
caterpillar species.
And, you know, you may look at it as a good thing or a bad thing,
because this virus is not going to have any negative impacts
on your beneficial insect species that you have out in the field.
But the downside is, is that if you have multiple caterpillar species
that you're trying to control, it'll only control the corn earworm.
Now, what's important
to make this virus effective is that it needs these worms need to be
under half an inch long.
We prefer a quarter inch long worms that half an inch
is good enough with this virus.
And if you kind of look right here,
that's about what size worm is the maximum that you want to spray
with this virus. It's just right under half an inch.
As you look at that worm, that's too big of a corn earworm
to be able to spray with this virus and get effective, reliable control with it.
So another question that we get commonly
is how long will this virus stay out in the field?
I've personally seen it stay out in a soybean field as long as forty one days.
You have to remember that this is any like any other virus
that like the flu or anything like that, is that it spreads around throughout here.
As long as there's other caterpillars that can become infected with this virus.
out in the field,
then this virus can continually keep reproducing inside those caterpillars.
I'm still seeing a lot of moths out here in this field,
and they're continually laying eggs when those eggs hatch,
they eat. Those dead larvae that are already out there in the field
are just full of virus particles and they infect those larvae,
well, whenever they start eating out here in the field.
So this virus can persist a very long time
and it can really help growers out as long as you've got worms out there.
This virus will just keep on reproducing out in the field.
That's kind of what we've got today.
And we'd like to thank the Soybean Promotion Board for funding our research.
And thank you very much.