Jonathan:
Safe use of the Tree Row Volume (TRV) concept rests upon the
assumption that there is a known relationship between tree row volume
and volume of water required to give
100% wetting of all foliage when spray is applied under the
conditions routinely used in a given orchard. I think it is
reasonable to doubt that such a relationship is
known by every grower for his particular situation. It is just as
reasonable to doubt that any such relationship between TRV and Dilute
Water Volume will be the same
for every orchard. The volume of water that impinges on tree
surfaces is affected by tractor speed, wind speed and direction,
distance of tree surfaces from the sprayer,
spray droplet mass, density of shoots, limbs, and foliage;
arrangement of limbs and foliage in regard to how it interferes with
open access to spray penetration....and so forth.
How all of these factors work together to result in a particular
Dilute Water Volume per acre, can be assessed with the use of
commercially available water sensitive papers
placed throughout the tree. Alternatively, the papers may be placed
only where coverage is critical, but difficult.
Drive past the decorated tree, spraying with all the same settings
as will be used for pesticide application, but apply water only.
Drive several alleys with the water spray...
all of those from which significant drift would reach the water
sensitive papers. Obviously, the determined Dilute Water Volume will
vary according to the time of year the
test is done, so such tests should be repeated as foliage density
increases; or some reasonable means of estimating the consequence of
foliage density should be used.
In using the water-sensitive papers technique, I think it best to
set the sprayer at the gallons per acre rate that you will use in
your pesticide applications. That is,
if you apply 50 gallons per acre in an Apple Maggot spray in a given
block, do the water test for that block at 50 gallons per acre
settings. Drive as many passes in the test
row as needed to produce a nearly 100% blue color of the least-wetted
papers in the tree. Then calculate the Dilute Water Volume, e.g. 50
gallons per acre X 4 passes = 200 gal/Acre.
Use a pesticide rate that will apply the label-recommended ounces per
200 gallon acre in the 50 gallon volume that you use per acre. Any
pesticide reductions you take for lack of
run-off are at your own risk, until you have determined from
experience that such reduction may be justified.
This determination takes time, but if you do it, you may be
surprised to discover considerable disagreement with the Dilute Water
Volume values that you had assumed,
based upon table values of TRV versus Dilute Water Volume.
David Kollas
Kollas Orchard
Tolland, CT
On Jan 15, 2010, at 12:58 PM, Jonathan B. Bishop wrote:
I am wondering how other growers/subscribers to this list determine
rates of application for pesticides to fruit trees on your farms.
We have used the Tree Row Volume methodology since the 1960’s
without any adverse effects. Explanations of Tree Row Volume (TRV)
and methods for calculating it appear in virtually every pest
management guide that is published, so I had assumed that this
practice was pretty much the industry standard. That is until this
season when I became aware that some pesticide manufacturers do not
recognize it or allow it to be used in determining the application
rate of their products.
We suffered extremely high incidence of damage from Apple Maggot in
2009 while using DuPont’s insecticide, Avaunt for control of the
pest. An investigation by DuPont determined that I was at fault
because by using Tree Row Volume I had applied the product at less
than the specified rate per acre (planted acre). They did not
assert that I had made in error in calculating TRV, but I was at
fault simply by the fact that I had used the methodology at all.
My contention is that I had applied the required 6 oz. rate in 50
gallons of water ( 6X concentration on a 300 gallon dilute tree),
but had reduced the amount of gallons applied to different blocks
of trees based on the smaller size of the trees. Since fruit trees
are three dimensional objects, I liken the principle behind Tree
Row Volume to painting houses. If you have two houses on one acre
lots, one being a 5000 square foot house and the other a 2500
square foot house, you don’t apply the same amount of paint to both
structures just because they are both houses on one acre lots! You
would (hopefully) require less paint to give the same level of
coverage on the smaller structure as a larger amount would give on
the big one.
This is not, apparently, the logic used by the chemical
manufacturers in determining the per acre rates for their products
and what I have learned from my experience with DuPont is that if a
grower in any way reduces the rate of product applied to an acre of
fruit trees, they do so at their own risk. By their logic, if you
shut down nozzles when going from a block of larger trees to
smaller ones, you would need to slow down, add pesticide to the
tank or nozzle up (to put the same number of gallons of spray
mixture per acre through less nozzles) in order to maintain the
rate per acre specified on the label. I would think that this would
over-dose the pesticide on smaller trees, but this is what I have
been told by DuPont in their official response to my questions.
They assume no responsibility if the rate per acre is reduced in
any way from what is stated on the label.
This industry, the chemical companies and the regulatory agencies,
that mandate what and how information appears on pesticide labels,
need to recognize that there is a difference in how we spray and
calculate rates on vegetable fields, which are virtually uniform in
height and ground coverage, and in orchards where there is
considerable variation in the amount of area covered by the
cropping surface. Unless we can develop a standard methodology to
differentiate a planted acre from a sprayed acre (volume) ( I
thought we already had one with TRV ) we are bound to increase the
amount of pesticide use (and residue levels at harvest) instead of
reducing it.
Regards,
Jonathan Bishop
???????????????????????????????????????????????????????????
B.W. Bishop & Sons, Inc. Bishop's Orchards
1355 Boston Post Road Growers of Fine Fruit
Guilford, CT 06437 Since 1871
Vistit us on the web at: www.bishopsorchards.com
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<http://www.virtualorchard.net> and managed by Win Cowgill and Jon
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Apple-Crop is not moderated. Therefore, the statements do not represent
"official" opinions and the Virtual Orchard takes no responsibility for
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