Managing Insects Economically Using Conventional Hybrids and Thresholds

Managing Insects Economically Using Conventional Hybrids and Thresholds


Welcome to the grain management and low
margin years video series. I’m Brian Jensen with the IPM program and UW
extension at the University of Wisconsin-Madison. My topic will be
managing insects economically. I’ll cover three topics. One including independent
crop consultants using conventional hybrids and also a little bit about the
economic thresholds. It may seem unconventional to talk about hiring
independent crop consultants in a year when we’re trying to reduce costs but I’ll
cover some of the advantages and disadvantages of hiring independent crop
consultants. As far as using conventional hybrids, we’ve seen a shift with growers
trying to save money going from GMO hybrids back to conventional corn. Quick
update on how that can be done efficiently so that you’re not caught by
surprise with any problem on down the road, and also you can save money using
economic thresholds for managing insects. What is an independent crop consultant?
There’s no official definition. I’ll kind of give you what I think an independent crop consultant is. It’s one who offers consultative services. They
receive the majority, if not all, of their income from those services, and there is
minimal connection with compensation from sales. Some of the services that an
independent can’t provide it will vary quite a bit from one consultant to the
next but some of the services may include Routine Field Scouting, Soil and/or Plant Tissue sampling, input recommendations for insects, weeds, and
diseases, input and recommendations for crop nutrients, as well as crop
production in general. They may also help you with conservation planning, nutrient
management planning, and crop budget analysis.
Some of the advantages that timely field scouting leads to improve control. You’re
catching weeds at an early stage, insects at an early stage where they can
be easily controlled. As a result that’s going to reduce crop losses. It also
avoids unnecessary applications, and it helps develop a pest history over time
so you can make decisions. For example with secondary insect pests like white
grubs and wireworms rather more efficiently. Any better crop
consultants walk a lot of acres. They see a lot of pests and they have first-hand
experience with monitoring those acres. The majority of independent crop
consultants are certified crop advisors. That is a program that’s administered by
the American Society of Agronomy it indicates a base level of knowledge in
that each certified crop advisor has to pass two comprehensive exams. Also,
continuing education units are required to the extent that within a two-year
period of time they have to attend 40 credit hours of training. Certified Crop
Advisors or CCA’s also have to adhere to a code of ethics, which includes client
confidentiality it also indicates that they should protect the interests of the
clients by recommending only those products and/or services that are in
their clients best interests. They shall not give professional opinion or advice,
make recommendations without being thoroughly informed, and also ACCA should
not issue a false statement or false information even if directed so by the
employer. Independent crop consultants also
provide you unbiased crop management advice in that they are not connected to
sales or if they are sales should be a very small portion of their business. You
hire independent crop consultants and they work for a limited number of people;
that being you can get in touch with them easily, and they will get back to you
because of their somewhat low client load, and also all information they
provide to you is confidential. Basically they provide you with all the
information that you will need to make sound management decisions. And finally
they provide peace of mind, and peace of mind is going to vary the value of peace
of mind is going to vary from one grower to the next, but I think one of the
advantages is that they provide you that peace of mind knowing that your crops are
being monitored, and that the best recommendations are going to be made
available to you. Some of the disadvantages. There is a fee associated
with these independent crop consultants, that is how they make their living. You
can do the field scouting yourself if you have the training, the experience, and
especially the time. There is no reason why you can’t do that scouting yourself,
but it just takes a little bit of time. Anyone can claim independence, do check
references, and also ask for whatever connection they might have to sales. Also
disadvantage of independent crop consultants is that their management
philosophies can vary from yours. Check references, talk to them about their
general philosophies towards pest and crop management, and see if the two
of you get along. When considering hiring a consultant,
if you do, it’s not for everyone, as for their background education, their experience,
and any references that they would be willing to provide you, and also ask
about their continuing education plans. What meetings, what conferences they go
to, to stay up to date. Now for that second topic that is switching to
conventional hybrids. Do consider why did you switch in the first place. I think in a
lot of cases you might answer for convenience. That may not be the only
reason, but I think one of the top reasons and arguably so, is a lot of
people switch because the convenience that the GMO hybrids provide. If
you make that switch to conventional hybrids, are you prepared to do the field
scouting, or accept the risks if you don’t, and are you prepared to make their
control recommendations if needed. There are some costs involved with
switching to the conventional hybrids. On this screen I have some estimates for
what the different traits might cost you. Your actual costs may vary up or down a
little bit but these are baseline ballpark estimates. The estimates that I
have gotten for the above-ground traits are roughly sixty-five dollars per bag
on the average with a range of between thirty-five and ninety dollars per bag. For that
trade corn with both above and below ground traits an average is 125 dollars
per bag with a rang between 100 and 175 dollars per bag. When comparing the cost
of these traits don’t just look at prices, do compare genetics. Make sure
you’re getting value there if you go with conventional hybrids. Also when comparing
the individual traits, look at the insects that are controlled, as well as
those that are suppressed. Suppression means a much lower level of
control, so that’s important to know and understand. Okay some things to consider
when switching from the below ground traded corn. First is remember that corn
rootworm control is only needed on continuous corn. There is no reason to
have the GMO hybrids for first year corn. However there are some exceptions in the
southern and southeast part of Wisconsin. In the past the Western corn rootworm has
been known to lay eggs and soy beans. If that is the case, you may need some level of control on first year corn, but in the past, including this year, most people and
I’ve talked to they have not seen that phenomenon of root worms laying
eggs in soybeans much in recent history. Also remember that most at plant soil
insecticide treatments for root worms are restricted use pesticides, meaning
you have to be trained and licensed before you can buy and/or use them. There
are two exceptions; large man 15g is a general use pesticide. You can buy that
without any training, without any licensing, and also seed treatments
are general use insecticides. Some application considerations prior to
using that plant soil insecticides. Number one: is your planner equipped with
granular insecticide boxes, whether they’re the old style open delivery boxes,
or the newer style closed delivery boxes. I guess what I’m getting at here
is when you make that switch from traded corn to conventional corn, and if you’re
going to be growing continuous corn, you will need options to control corn worms
and to consider ahead of time the cost of those boxes.
If you’re not going to use the boxes you’ll have to plumb your planner for
the liquid root worm insecticides, or if you have dry starter fertilizer, you will
need to equip your planner with liquid fertilizer units, and also regardless of
which method you use to control corn rootworms, you’ll have to make sure that
all application methods are calibrated properly. I got some estimates on the
cost of insecticide boxes. There are some used ones out there available. It’s kind
of a range between seventy-five dollars per box upwards of 250 dollars per box.
New units, whether it’s for a finger tight planter or the vacuum planters,
were pretty consistent between 400 to 500 dollars per roll. Another option for
the granular insecticides are to use the Smart boxes. Without mounting
brackets the costs that I’ve seen are approximately four hundred dollars per role
for a 48 row planter, and that goes up with the economy a scale to five
hundred dollars per 12 row unit. Also starting this past year in 2016, there is
another delivery method that’s a thrive 3D system which uses capture thrive 3D
insecticide or formulation. There are startup costs for that, and they roughly
twenty-seven thousand dollars total for a 24 row system, or 20,000 for a 12 row
system. Also there are rebates included with product sales and things
like that, roughly about sixty dollars per gallon. I guess my point with this
slide is when you do make that conversion from the GMO hybrids or
traded hybrids or conventional corn, you need to have some method to control them, and if you don’t have that method to control root worms, these are some
approximate costs that it might take to equip your planter. In looking at the cost
of seed treatments, they are about four dollars and eighty cents per acre as compared
to the soil plant insecticides, you know there’s a bit of a range there depending
on product. Anywhere is between nine dollars and twenty dollars per acre,
with an average of you know roughly fourteen or fifteen dollar per acre. Do
keep in mind as you make that switch from the traded hybrids to the
conventional hybrids, there is an additional value to doing so. What I’m talking about is Bt resistance management. There is quite a
concern in the last few years in preserving these Bt hybrids and to help
preserve them, we need to diversify our management practices that could include,
certainly will include rotation, seed treatments, as well as soil applied at
plant insecticides, so there’s extra value in going to the
conventional methods of rootworm control. As we’re making that switch or anticipating
making that switch let’s consider the efficacy of the soil applied
insecticides, in other words how well to the individual insecticides work. I’ll
provide you in a slide or two our rootworm efficacy trial data, and what I call it
is my consistency data from the years 2001-2013. I don’t have data for you
prior to that because we’re on a different evaluation system than what we
are right now, and our numbers are not backwards compatible to the old
system of rating corn roots, and in 2014 to current day we use a different method
of attracting corn rootworms into our plots and Nexus I get extremely high numbers
or beetles so I at least for the time being I’m concentrating on the years
2001-2013. To consider an insecticide that
has acceptable control, it needs to perform lower than a 0.5 injury scale,
meaning 0.5 there’s one half of a node of roots that are pruned back. I think
most entomologists will assume that actual threshold is 0.75 or
three-quarters of the node roots pruned back. I’m being a little bit
more conservative with my estimate for these consistency ratings. Also for an
insecticide to be included in this consistency data, the untreated check had
to have significant pressure, and in my rating system that nodal injury scale
had to be greater than 1.0 or 1 complete node of roots pruned back. All
plots were conducted at the UW-Arlington AG research station. In corn following
late planted corn, which served as a trap crop, that guarantees me damage, it also
guarantees made fairly high pressure of root learn beetles. So my point there is
that these are usually populations that are quite high, higher than what you
might expect to see in most fields. I only use data from those treatments that
were applied at the current rootworm labeled rate. A lot of times we’ll have
different rates that we’re looking at in order to dial in an acceptable
range for control. I only used those rates that were labeled.
Data from experimental formulations although were the same active ingredient, were
not used, and I lumped all placements together both pearl and T ban. Over the
years we don’t see a big difference between the two, as well as all
application methods were clumped together, whether it was an open
delivery system or a closed deliver system. Here’s a table that I was
referring to. For example in that top row we have both Aztec 2.1, Aztec 4.67.
They’re both granules, there’s soil applied, and in that top row Aztec 2.1
provided me a high consistency rating in 21 out of 30 trials, and Aztec 4.6G,
2 out of 3 trials. Capture not looking as good for us in recent years. It might
be an insecticide that’s better suited for fields with low populations of corn
rootworms. Counter 15G and 20G, four out of five years have provided consistency.
Not a lot of trials that are represented here in part because counter was labeled
long ago, and we had done a lot of work with counter both formulations, as well as
other formulations under that old rating system that is not forward compatible to
our current rating system, but there is no reason for me to think that the
formulations of counter would be any different than what we see on on this
chart. Force 3G, 18 out of 29 treatments that look good. That was a bit
surprising to me going back over the data. I still consider that fairly good
results, and again, these are our trials under extremely high rootworm pressures.
Force CS, or the liquid formulation, provided us acceptable control in nine out of nine trials, and that final line is Lorsban
15G not so well. That is one product that is of general use, and because of
that consistency data, I guess I would prefer to have someone to get
trained and certified for the other restricted use products that you see
listed above. This next slide is for the efficacy of seed treatments put in the
same trials, and again this is corn planted after a trap crop, and
it’s a situation where you would expect extremely high damage. It is not a
situation where I would want to put a seed treatment in to control corn rootworms. I
guess my point it’s not the damage in my trials would have been higher than I would
expected the sea treatments to work but they still did relatively good, working
in about a third of the trials. We can get additional value from our
conventional hybrids if we scout fields for beetles. Roughly one to three field
visits during that period of time when the adults are laying eggs, that’s early
August through early September, and the threshold is if we see more than
three-quarters of a beetle per plant on a field average, we do need to treat or
rotate out of corn in that till next year. If we’re below that threshold of
0.75 beetles per plant on a field average, we don’t need to treat at
all. So the value we get from that field scouting is this: if we find in the
previous year that we have extremely high beetle counts, our options would be
to rotate, use soil applied insecticides. I think they will work adequately, or
quite well if we choose the right insecticide, and also
you can maybe on in these fields you would want to consider using a GMO
treated hybrid with a below ground trait. On those fields with medium beetle
populations, rotation is still a real good method of control, and it is
certainly a place where I would consider using soil applied insecticides. If we’re at threshold, again rotation is still an option, the soil applied insecticides
are still an option, but that is also a situation that I might consider using AC
treatment. Here I have documented low beetle populations, and that would be an
instance where I would expect the seed treatments to provide adequate control. Some people wonder is it worthwhile to
scout for beetles with the assumption that all continuous corn fields need some
form of beetle control the following year. If we look at this map developed by
the Wisconsin Department of Ag, Trade, and Consumer Protection it kind of
highlights the variability we have in beetle populations around the state. If
you look at that map closely the red dots are those fields that are at or
over threshold. Those fields will require some form of control next year in 2017.
Those fields with a yellow dot are just below the economic threshold, kind of
what I would term a slightly below economic threshold I guess I should say.
Those that are green dots have very light beetle pressure of 0.1 to 0.4
beetle per plants, and all of those black dots are fields where the survey
personnel could not find any rootworm beetles in that field. So my point with
this slide is beetle scouting can be worth your time and effort, and I think
all those red dots kind of indicate that. They’re based throughout the state,
it’s not just the southern part of the state that has high beetle pressure, but also
given that there is still a lot of variability from one field to next for
rootworm populations. Okay in recent years with perceived high beetle
populations, people have been adding a soil applied at plant insecticide with
rootworm traits. Let’s look at that as a possibility for saving dollars as well.
If you have a single rootworm trait, it is not going to pay to use a soil applied
insecticide with that trait unless you have extremely high beetle pressure. If
you’re using a dual hybrid with dual traits, or a pyramid hybrid, I cannot
think of a reason why adding an at plant soil applied insecticide is necessary. I
would expect under all circumstances that pyramid hybrid to provide adequate
control for corn rootworm feeding. Now let’s look at switching to
hybrids going from those with above-ground traits to conventional
hybrids. The four insects I’ll talk about briefly are European Corn
Borer, Western Bean Cutworm, Black Cutworm, and also Stalk Borer. Current population
trends based on DATCP surveys for corn borers, in 2015 we had historic
low populations. That was based on the 74 year history of the corn borer survey/
In 2016 we had somewhat higher populations, slightly higher populations,
but also in some cases they were regionally higher but those higher
populations were very isolated in individual fields. So if
one is considering going from the traded hybrids to the conventional, quite
frankly in 2017 this might be a very good time period to do that because of
low corn borer population. Western Bean Cutworm in general over the last few years
populations have been low in Wisconsin, but regionally high in
the central part of the state. Blackout worms which are an occasional pest and
can be controlled by some of our traded hybrids. I think we need to remember that
they’re an occasional test. You will not get value from that above ground trait
each and every year. Black cut worms are easily scouted for, and we have economic
thresholds available to use to help you decide when is the proper timing for
control, for control I’m talking about using broadcast foliar applied
insecticides. Application timing is going to be somewhat critical, but as long as
we’re scouting our cornfields between v1 and v4, we’ll be well ahead of any
potential cutworm problems. Also the last one I’ll talk about is Stalk Borers.
Again it’s an isolated pest. Usually it’s found along field edges, next to
grassy waterways, terraces and/or weedy areas of field. It’s easily scouted as
long as we’re scouting our early stage corn, V1 through V4, we can identify
problems early on and come back with a well-timed treatment which usually can
be what we would call a spot treatment just treating those areas of the field
with Stalk Borer. Let’s take an example of first
generation European Corn Borer control without traits. What I would suggest
doing is to start scouting my fields mid-June at about 600 growing degree
days, and I would focus my energy on the earliest plant of cornfields first.
They’re going to be most attractive to the adult to come in and lay eggs. The
economic threshold we’ll talk about briefly, it is available in some of our
extension publications. Each larvae will cause about a five percent yield loss
in first generation. Let me give you a scouting scenario. Let’s assume that we
were out scouting, and we found that fifty percent of plants were infested
with an average of one larvae per infested plant. That’s a field average of about a
2.5 percent yield loss. Let’s assume a expected yield of 180 bushel
per acre times a 2.5 percent yield loss, we’re looking at
losing about 4.5 bushels in that situation. We’ll assume a selling
price of four dollars per bushel. In that case we would expect about eighteen
dollar per acre loss from Corn Borers in that field. Then you just merely compare
your treatment costs with that $18 per acre loss for Corn Borers. Second
generation is going to be a little bit more difficult I think to control. We do
scout for egg masses. As far as control expectations, do remember you’re scouting
tasseling corn, you will need a high-clearance sprayer. If you need to
treat one of the other problems with a second-generation corn borer control,
it’s about a two week flight period so timing of control will be very
difficult. It will be difficult to get complete control with one application,
but also what helps a little bit is there’s a lot of other hosts around the
countryside that corn bores can be attracted to to lay eggs, and if you do
find yourself with unexpected second-generation corn borer damage, you
can always consider that field for early harvest. Black Cutworm Management, again,
remember it’s an occasional pest, we do not have a problem with it each and
every year. To scout for it I would suggest you go out and spot check fields at
emergence, and those fields out of wood spot check are those fields with soybean
residue. The adults, for some reason, are really attracted to that soybean
residue to lay eggs and there are fields with a lot of broadleaf weed growth early in the spring. The economic threshold for Black Cutworm would be to
treat if you have five percent damage plants, and in this slide you can see a
Black Cutworm in the upper right hand side, and the range of damage that Black
Cutworms can do, and the lower left we see a little bit of leaf-feeding. That’s
important to note that damage is not considered economic; that is damaged
from a very small larvae on seedling corn, and it gives you a little head up for what
could be coming. In that middle bottom slide are some classical symptoms of
cutworms cutting plants off at ground level, and in that slide furthest to
the right is what we call wilted whorl or dead heart. That’s from a large Black
Cutworm larvae burrowing into that corn plant below ground level. And finally
let’s talk about using economic thresholds as a method for saving
dollars in these low margin years. First, what is an economic threshold? It’s that
pest population that needs to be controlled to prevent, and that’s an
important part of the definition, to prevent economic loss.
Using these economic thresholds incorporates dollars and cents into our
control decisions. Also, economic thresholds that have been developed for most field
crop insects, if not all field crop insects, at least the major ones
certainly have economic thresholds developed. I’ll talk a little bit about
the soybean aphid economic threshold and walk you to that as a scenario for
economic thresholds. For soybean aphids, that threshold is a three-part threshold.
We need to have an average of 250 aphids per plant
on eighty percent of plants, only during the R1 through R5 growth periods. Soybeans in
the vegetative stages, although you may find soybean aphids on, they do not cause
economic loss, at least that we have ever been able to measure, and growth stage six
and beyond soybean aphids do not cause economic loss, primarily because most of
our yield has been made by that R6 growth stage. These thresholds have been
developed through University collaborations; it includes close
monitoring of replicated research trials. Data has been gathered from multiple
sites and from several years across the soybean producing states including
Wisconsin. The results are, I hope, unbiased. They are developed by
University staff and faculty, and they are peer reviewed, and what I mean by
that is other entomology researchers look at the data, look at our results, and
they decide whether or not that information is
valid or not. Let’s give you a little more background information on the
soybean aphid economic threshold. At the economic threshold of 250 per plant, we have
not been able to measure yield loss, whether it’s economic or not, we have not
been able to measure yield loss. It is, therefore, a very conservative number.
It’s a very conservative estimate, and it’s important at that economic
threshold of 250 per plant that the population is increasing because we can
measure economic loss somewhere between six to seven hundred aphids
per plant. Therefore spraying prior to the economic threshold of 250 per plant
will not be economical, and you’re probably wondering why have we set that
economic threshold so low. It’s two part, primarily because the population
dynamics of soybean aphids. They can increase in populations in a very short
period of time, therefore we want to give people a little lead time so that they
can prepare to spray. So again that’s twofold because the population
dynamics of a soybean aphid increase so quick, and also because we want to give
you built in a little lead time before you need to spray. So do you adjust the
economic threshold with lower insecticide costs or changing commodity prices? To be
truthful both of those situations have little effect on the economic threshold.
Again remember we do not, cannot measure yield loss at the economic threshold of
250 per plant. However there are consequences if we lower the economic
threshold, and spray before that. We will kill off beneficial
insects, and as a result soybean populations can and will rebound after
that, especially if those natural enemies are no longer present. As a result we may
have to spray a second time. Also secondary insect pests, for example
two-spotted spider mites may rebound in the absence of their natural enemies, and
we also have to remember, too, that as soon as we drive into that field,
assuming we’re using ground application, we will suffer some small yield loss just
because of wheel traffic. There are places to go for help. I’m sure in this
short video we have not been able to give you all the information you need,
and you may have questions coming up later. Always remember to contact your
local County Extension agent if you have any questions. Do consider getting a
subscription to the Wisconsin Crop Manager Newsletter. It’s a free
newsletter. You have the site to subscribe to it, and also the Department
of Ag hazard pest bulletins, as well as the site where you can subscribe to. The
Wisconsin Crop Manager will give a bit of a heads up on on past problems and
crop management problems we’re dealing with, as well as how to manage them. The
pest bulletins put out by the Wisconsin Department of Ag is an outstanding first
alert bulletin. That bulletin comes out on a weekly basis during the summer, and
it will give you a heads up for when they’re finding problems in the
field. Thank you.

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