this presentation on pesticide
resistance management by Katherine Ghantous and Hilary Sandler from the UMass
Amherst cranberry station and Laura McDermott from Cornell University was
made possible by funding from Northeast SARE professional development program
with special thanks to Margaret McGrath Andrei Alyokhin and Richard Bonanno for
their assistance and expertise. What is pesticide resistance ? It is an
inheritable genetic characteristic of a pest that makes it less sensitive to a
pesticide. It can occur in all types of pests; weeds, insects, fungi, etc. The pest
is able to survive a pesticide exposure that would kill those individuals that
did not have those genes. The genes naturally occur in the pest population.
The pesticide does not create a mutation, does not cause these genes to occur. They
are already present in the population of pests. What happens is that the pesticide
used will select for resistance. It does that by killing susceptible individuals,
or those without the genes, and those with the genes are able to survive. They
are selected by the pesticide exposure. Pests with the gene will live, reproduce
pass on the genes for resistance to their offspring. The resulting pest
population will have increasing numbers of resistant individuals. In this natural
pest population, there are some individuals that have the genes that
make them less sensitive to the pesticide. In this case insects, the red
ones, have the naturally occurring genes. A pesticide application occurs and what
happens is that the individuals that are susceptible will die. In this case most
of them and a few that have the resistant genes with survive the pesticide application. The individuals with the naturally occurring genes, that make
them less sensitive to the pesticide, will survive and after the pesticide
application. After the humans have applied this type of selection pressure
to the population, the less sensitive pests that have survived, will reproduce
and the resulting offspring will have the genes that make them resistant to
the pesticide. This does not happen in a single
application, resistance takes time to develop. So even if on your particular
farm situation you have a lot of resistant individuals, there are much
more populations of these pests that occur outside of your farm as well. And
there’s a lot of flow of individuals between off-farm populations onto your
farm, which is good so you have the constant
influx of genes that stop this population from being entirely resistant.
However, on the converse side there’s also a flow of genes from your farm into
the native populations. After time as I said resistance takes time to develop if
there’s enough pesticide exposures on your farm there’s enough of the
selection pressure applied again and again over time the individuals will
enter the wild populations and over time resistance will become more widespread. Because resistance takes time to develop,
it gives us an opportunity to use techniques that can forestall or delay
or even prevent the development of widespread resistance. If an insect
population is resistant to a particular pesticide, in this case the green spray
at the top, that pest will likely not be resistant to other types of pesticides
that are not within that same group. So by rotating between pesticides what
happens is that you can remove some individuals that are resistant to the
first pesticide from the population with an application of the second pesticide.
We have seen resistance develop and cramp the cranberry industry already. We
have two particular poignant cases of this the first is weevil.
So this pest of cranberry is now resistant to all organophosphates and
the resulting pesticide that we use to control it, Avaunt, we are now worried
that it’s developing resistance to Avaunt. Spag is another example of a cranberry
pest that is now resistant to organophosphate and that we have a worry
that it might be developing resistance to Delegate, which is the pesticide that
is now used to control this pest. An example of weed resistance a good
example of this is when we look at Roundup Ready systems in this case we’ll
talk about the soybean system agricultural scientists have created soy
plants that are unaffected by glyphosate exposures, what this means is that soy
growers could then spray glyphosate over the top of their crop and kill all of
the weeds in the field leaving their crop uninjured.
This really simplified weed management it was a great tool when it first
appeared on the scene, however increasing glyphosate use both the frequency and
the large number of acres treated have increased the probability of selecting
herbicide resistance plant. Here’s a picture of a soybean field after a
glyphosate application, the weed here is horse weed. You can see here that a
lot of the horse weed has died off. These brown desiccated individual horse
weed plants but you can see that there are also quite a few number of horse
weed plants that have escaped this glyphosate exposure and have survived.
What happens now over time is that glyphosate resistant horse weed now
infects millions of acres from Delaware to Illinois. In addition to horse weed,
there are lots of other weeds that are also becoming resistant to glyphosate.
Pigweed/Amaranth ragweed and many others as well. So why is managing
resistance important? Well pesticide resistance is increasing,
currently there are at least 520 insects and mite species and of these 17 insect
species are resistant to all major classes of insecticides not just one.
There are over 273 documented weed species 150 plant diseases and ten
rodent species that have some type of pesticide resistance documented. There
are likely many more that we are not aware of yet. So why is managing resistance important? Well, we need pesticides to provide an effective
control of pests. We use pesticides because we we need to control pests. New
products for pest control are very hard to develop and if the current technology
that we have available to growers stops working it might be a very long time
until something comes along to replace it. We also need to practice good
environmental stewardship. Pests are mobile and resistance that develops in
one crop or one area can easily spread to other crops or other areas. And again
if we’re using ineffective pesticides we’re causing unnecessary risk so every
pesticide use is associated with some type of risks both to the human whose
applying it, the environment and so on. And, we take these risks because we
deem them worthy. However, if our pesticides are not working then we’re
using taking these risks unnecessarily. As I mentioned all types of pests and
all types of pesticides are at risk for resistance. Herbicides, fungicides, and
insecticides each one of these types of pesticides has a
resistance action committee that’s been developed. And these are international
groups that are founded by the agro-chemical industry for cooperative
approach to resistance management. They’re excellent sources for
information and education materials related to each class of pesticide. The mode of action is the chemical structure of a pesticides that defines the target
site, which is the physical location within an organism where the pesticide
acts. The mode of action is the action of a pesticide added target site, the way in
which it causes a physiological disruption at the target site. Each
pesticide has a group number that was assigned to it by the
resistance action committees for that type of pesticide. And these group
numbers help growers make resistance management decisions. The group number
should be clearly marked on all pesticide labels. Herbicides have two
separate groupings , one’s assigned by the herbicide resistance action committee
and one is assigned by the weed science Society of America. The HRAC will use letters for their codes they’re very, very
similar slightly different, but in most cases they will be in alignment
with one another. So you can see here I have an example of a label from Select
Max, which is a Clethodim product. Right on the top of the label it will say it’s a
Group 1 herbicide. If you then go and look at the information about what this means. In this case Group 1 it will tell you the site of action
it will tell you the chemical family and it will tell you other active
ingredients that are within this same group. The same is true for insecticides,
they all have a code that’s been assigned by the insecticide resistance
Action Committee. Here is a label for Lorsban. Right at the top of the label
it tells you with the group 1 B insecticide. If we then go look at the
insecticide resistance Action Committee website we can learn from that that 1 B is an organophosphate and it will give you a large number of other
pesticides that are within the same group. The same is true for fungicides the
fungicide resistance action committee code clearly marked at the top of this
label for a product called Abound. Group 11 In addition to the group
numbers labels also have a lot of good information about resistance management.
Sometimes there’s recommendations on the number of fungicides the sprays and
other types of things that one can rotate to, so I urge you to consult the
label for your pesticide to look for this type of information when making a
plan for your farm. In Cranberry management we put out a publication
called the cranberry chart book every year, and in this particular publication
we have detailed information about the different groups and the risk of
developing resistance. What we can use these numbers and these
groupings to do is to help us alternate rotate or sequence different pesticides
to help forestall resistance management. By using the codes when you’re choosing
your material now you have to use the codes that’s very important you can’t
rely on product names or active ingredients because many different
products and active ingredients can be in the same group. In this case here if
you were only looking at the product names to plan a rotation or sequence and
you’re saying I’m using Aftershock and then I’m using a Evito I’m using two
different products. In actuality these two products are both group 11 fungicide
so this is not a good rotation they’re within the same group. If you were only
looking at the active ingredients to plan your year rotation or sequence and
you’re saying oh these two products have two different types of active
ingredients if I alternate or rotate between these two then perhaps I’m doing
a good rotation or sequence but in truth these are both group 3 fungicides so
this is not a good rotation or sequence You want to look at the group numbers to
plan your sequences so to plan a true rotation or sequence you would want to
move between 11, 3, 19, and so on so again you really need to be
using these numbers not the names and not the active ingredients when you’re
planning on rotations or sequences for pesticide resistance management in
addition to choosing chemicals from different groups. Applications must be
timed correctly you really should be targeting the most vulnerable life stage
of the pest and you should be using spray rates and application intervals
that are recommended by the manufacturer, and that are in compliance with global
Agricultural Extension regulations. A high rate may possibly take out pests
that might be somewhat resistant but if you’re using a rate that’s too low it
may allow the resistant individuals to survive and reproduce so rate selection
is very important. There are many challenges to managing resistance some
products with resistance risk for one pest are also used for another. Pesticides don’t only work on the target that you’re targeting you have a large
ecosystem in your field so even if you’re targeting in
this case you’re using delegate to control black-headed fireworm in
Cranberry you’re also exposing the spag and the other bugs that may be present
on your farm but that are below the action threshold and you’re not
necessarily targeting. Some key points about managing resistance the goal is
delaying the development of resistance not managing resistant pests biotypes
once they are detected so once the resistance exists is more difficult to
manage than it is to use good practices to avoid the development of resistance
in the first place. You should always be using integrated pest management
programs on your farm and you should when at all possible minimize the
use of at-risk products. When we look here again this is an example from the
cranberry chart book that might this type of information is likely available
for other crops as well. You have in addition to information about the group
number the trade name the mode of action and the chemical group you also have
some information about the risk of development of resistance so some
chemicals are high risk and others are lower risk so when at all possible
choose a lower risk product and you should not be relying on pesticides
alone it’s important that you integrate different controls into your management
program in addition to synthetic pesticides there’s biological pesticides
there’s beneficial insects there are cultural practices for weeds you can do
hand weeding and so forth and there are chemical attractants and deterrence that
can be used so by implementing all of these tools together you have a program
that is less susceptible to developing resistance to pests developing
resistance to pesticides thank you for your time.