Late Season Insects In Soybeans (From Ag PhD Show #1110 – Air Date 7-14-19)

Late Season Insects In Soybeans (From Ag PhD Show #1110 – Air Date 7-14-19)


B: Late-season
insect scouting in soybeans is so incredibly important. Today we want to talk about
a few of the different bugs you might find in your
fields. D: Well soybean aphids, Brian, are going to
get most of the attention. They’re this pest that when
you get a heavy aphid infestation, it’s a disaster
out in fields. But, I do want to focus on some of the
defoliators too. B: Let me just summarize what we want
you to know when you walk out into that field. Number
one is that Darren mentioned defoliation. Ok, defoliation
is only a small part of yield loss. So when we look
at this yield loss overall from losing part of a leaf,
just look at the hail charts. Go to Iowa State’s
hail charts or University of Nebraska’s hail charts and
that’ll show you – it takes a tremendous amount of
defoliation to lose yield, unless you get disease in
there. The problem with defoliation by bugs is that
many times the insects are carrying disease into that
plant. So that’s the big reason why we don’t want
those bugs defoliating the plants because they’re
injecting a toxin or a disease into the plant very
often. Yes, anytime a plant is defoliated slightly, it’s
got open wounds, now you’re more likely to have both
bacterial and fungal diseases. But I do worry
most about insects, as opposed to wind and hail
damage. D: Well certainly, Brian, that disease problem
could be an issue as you open up the plant and here’s
why we put a fungicide oftentimes whenever we’re
spraying an insecticide, and growers who do that say year
on year, they’re going to see a good average gain over
time. But when we look at just for the defoliation,
take the disease piece out of it, take the fungicide
piece out of it – do you wait for 25% defoliation? Do
you wait for so many plants out of ten to have leaf
defoliation on them? B: Yeah but you can’t take disease
out of it and that’s the whole thing. What we’re
really after here – here’s the thing – when you walk
into the field, every time when you’re finding harmful
insects there, you have to ask yourself the question,
“Have I reached an economic threshold?” So you’ve got
the defoliation part, you’ve got the disease part; you’ve
got to put those together all the time. I can’t ever
just separate the one from the other. And you have to
say, “Alright, is it going to pay to treat?” When I
look at the insecticides, most of them cost two
dollars. The cheap pyrethroids cost two
dollars. If you have some spider mites out there, you
need a spider mite type product, ok you might have
to spend 2-4 more dollars – maybe it’s a little more
than that. But look at, “How much is it going to cost me
to treat and how much is my crop actually worth?” And
the whole thing is, as we go through this summer and
soybean prices continue to go up all the way into the
fall, well your crop’s worth more, which means the
economic threshold goes down. So for example,
soybean aphids – the threshold, I can promise
you, is not 250 aphids per plant. The earlier the bug
comes in the more chance you have to have disease, the
more chance you have to have yield loss. So what I’m
saying is, the earlier it is – the lower that threshold
is. Then the more the crop is worth and the less it
costs to treat. Ok, you got to look at those things,
that really impacts what your economic threshold is. For example, if I’m already
out there spraying fungicide or foliar fertilizer or a
biological, and I can just throw 2 dollars’ worth of
insecticide in – I only have to have a few aphids per
plant. Probably 10, maybe 50 at the most and I can
justify treatment when I look at today’s soybean
price and that very very low cost. D: The other thing
that’s really key here is get out and scout your
fields. So if you’re going to be spraying a field, get
out and scout. Do a sweep net through the field. See
what you’ve got out there for bugs, because – alright,
you may not have that many soybean aphids, but you also
have some bean leaf beetles, and you also have some of
these thistle caterpillars and green clover worms and
other bugs that are out there. They’re all going to
come together, it’s not going to be,“Well did I meet
the threshold on any single bug?” No, it’s, “I’ve got a
whole bunch of different bugs out there, and yeah,
I’ve got 10 of these and I’ve got 20 of those and
I’ve got 30 of those.” It’s a big deal and it does add
up on top of each other. You just have to scout first. I
don’t want you throwing insecticide in just saying,
“Well, just throw it in I’m going out to spray, I’m
going to save a trip.” Well, if you don’t have any bugs
out there, you’re wasting your money. And, if you had
one aphid per acre – well you’re wasting your money
too, and you’re killing off all of the beneficials
needlessly. If the beneficials have this thing
under control, and you’ve got no harmful bugs, there’s
no point in putting insecticide in. One other
thing to note is your insect pressure is likely to be
different between fields. So as you go into one field and
you say, “Man I got some bugs here – you go into
another field and you don’t see quite as many. One of
the things that we’ve heard a lot from farmers over
the last few years is, “Hey, if I put a seed treatment on
with a good rate of a neonic treatment in there, I don’t
have as many of quite a few of these species of bugs
including soybean aphids in those fields later in the
season.” So, yeah if you get some suppression with your
seed treatment that’s awesome, but here’s the
other thing – many of those companies with those seed
treatments have respray programs, so if you do have
insect outbreaks later, they help you with the cost. You
may even get free insecticide. So make sure
you check that out with your seed and seed treatment
providers. B: Alright, so even though it’s getting
later in the season and you might say, “Oh, my wheat’s
done, I don’t want to scout my corn anymore.” You have
to be looking at soybeans all the way into mid-August. Soybeans make their yield
late in the year – don’t let bugs rob that yield from
you, especially when the soybean price is going up
and when insecticide costs so little. Just make sure
you’re scouting at least once a week in all your
fields. D: It may not be too expensive to control some of
these bugs, but how much will it cost to control our
Weed of the Week? We’ll talk about this weed coming up
next.

1 thought on “Late Season Insects In Soybeans (From Ag PhD Show #1110 – Air Date 7-14-19)”

  1. Great quality produced, bite size videos you guys make. Include a tent for your field day to talk about video production. There are similar ag shows, but they're usually shot on a Soviet era camcorder, or the speaker mumbles basically 99 percent of the university videos

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