As you have surely noticed, the
directions for use on a pesticide label are quite
complex. An important factor to pay special attention to is the
application rate. One product can list many different rates
depending on the crop you’re working in, the pest you’re
targeting, and also the soil conditions. Let’s look at an
example of how the rate varies based on crop and pest. Say you are treating a foliar
disease on green onions with Quadris Flowable Fungicide. Note
how the rate varies depending on what pest you are treating:  
For powdery mildew, you see the rate ranges from 6 to 12 fluid
ounces of product per acre, but for downy mildew on the same
crop, you see the rate is different. It ranges from 9 to 15
fluid ounces of product per acre. Sometimes a product has
different use rates for the same pest on different crops. Let’s say you treated your
carrots for powdery mildew using the rate of 15.5 fluid ounces
per acre, which is within the label rate of 9 to 15.5 fluid
ounces. Now, let’s say you have powdery mildew on tomatoes. 
Can you use the same rate since you are using the same product? If you check the directions for
use, you will find there is a different rate for powdery
mildew on tomatoes, even though you are using the same pesticide.
The label rate for powdery mildew on tomatoes is much
lower, only 5 to 6.2 fluid ounces per acre. Another thing to note on labels
are maximum-use rates. Labels list the maximum amount of
product that can be used per season. I will explain
the maximum-use rates in the next example. Chinh is a broccoli grower who
had an alternaria leafspot problem last year. This year,
he’s decided to take preventive action. He applies Quadris
Flowable Fungicide at a rate of 15.5 fluid ounces per acre
before the disease develops. He’s planning to use this
product throughout the season and estimates that he will need
to make at least 6 applications at this rate. Can he do this?
Look at the attached label and see what you think. [No audio] According to the label, the
maximum-use rate for this product is 92.3 fluid ounces of
Quadris per acre per season. Six applications of 15.5 fluid
ounces is equal to 93 fluid ounces, which exceeds the
Quadris maximum use rate of 92.3 fluid ounces. Chinh either has
to reduce the rate or reduce the number of applications so that
he doesn’t violate the label. However, there’s something else
to take into account. The active ingredient in Quadris Flowable
Fungicide is azoxystrobin. The label states that you cannot
apply more than 1.5 pounds of azoxystrobin per acre per season.
So when you apply other azoxystrobin-containing products
such as Azoxystar or Quilt, those applications count towards
the maximum amount of azoxystrobin that can be applied
per acre per season. When looking at rates, Chinh
must also consider the resistance-management guidelines.
According to this label, only 2 applications of Quadris Flowable
Fungicide can be applied before rotating to another product that
is in a different fungicide mode-of-action group. All of this is important when
determining the application rate. Chinh should not make more than
2 consecutive applications of azoxystrobin-containing products
before switching to a fungicide with a different mode of action,
and the maximum amount of azoxystrobin applied to his
broccoli cannot exceed 1.5 pounds per acre. I mentioned at the beginning
that soil type is also an important factor when
identifying an appropriate application rate. Fine-textured soils are heavier,
predominantly clay soils, or soils rich in organic matter
with small pore spaces. Water and pesticides bind to them
tightly and don’t move as quickly through the soil. That
makes pesticides less available to root systems and soil pests. Soils with coarse textures are
the least absorptive and have large pore spaces so they allow
pesticides to move through quickly. These are
gravel-type soils. Some labels will recommend rates
based on your soil type. This Caparol label recommends
the standard rate of 2 to 3.2 pints per acre. Now consider
the following questions: If you are applying this
herbicide to cilantro and have coarse-textured soil, what
rate would you use? Since coarse textured soils
allow pesticides to move through quickly, you should use the
lower rate of 2 pints per acre. What about soil with high
organic matter content? Pesticides will bind to this
type of soil, so you should choose the higher rate of
3.2 pints per acre. Note that this is the maximum
use rate per crop cycle. And now what about sandy soils? This herbicide cannot be used on
sandy or loamy sand soils. To summarize: When deciding the
application rate of pesticides, make sure to check the
following three things: 1. Check the label for the
correct rate for your crop. 2. Verify the maximum-use rate
per season, and any resistance management restrictions, and 
3. Check whether there are any specific instructions for
applications on the soil type in YOUR field. Remember, follow all label rate
instructions so that you don’t exceed the maximum-use rate and
end up with illegal residues!