Comments on EPA Memorandum on 2005 Grower Impact Assessment of
azinphos-methyl use on apples (DP 307589)

Greg Krawczyk and Larry A. Hull

The Pennsylvania State University

Department of Entomology

Fruit Research and Extension Center

Biglerville, PA 17307

Phone 717-677-6116 ext.5

e-mail:gxk13@psu.edu

This document also include comments provided by Dr. James Walgenbach,
North Carolina State University

Summary of current uses of azinphos-methyl in Pennsylvania and Mid
–Atlantic region.  Azinphos-methyl (AZM) remains one of the most
widely used insecticides by fruit producers in PA and the entire
mid-Atlantic region.  With its wide spectrum of pest activity, AZM is
still listed as one of the best materials to control: codling moth,
oriental fruit moth, European apple sawfly, plum curculio and apple
maggot.  All of these insect pests are internal fruit feeders, a group
of pests that is responsible for close to 3000 rejections of fruit loads
destined to local fruit processors since 1998.  The processing fruit
standards enforced by USDA inspectors during fruit evaluation at
delivery call for rejection of the entire load if a single live insect
larva is found in the delivered fruit.  The detection of a single
“fruit worm” in the fruit results in rejection of entire load, often
1,000 bushels of fruit. 

AZM is also quite active against another group of pests called
leafrollers which affect the surface of the fruit: obliquebanded
leafroller, tufted apple bud moth, red banded leafroller and other which
can be found in our region orchards.   This group of pests, although not
the most important for our processing growers, is very important for the
fresh market part of our industry, where the slightest blemishes on the
fruit surface reduce the price for the crop and often can force the
grower to redirect fruit from the fresh market into processing.

Currently, an average insecticide program on apples for our region
includes up to four applications of AZM per season.  This high number of
applications is possible due to low usage rate of AZM in a manner that
still provides adequate pest control (usually at 1.5-2.0 lb per acre/per
application).  With our multi-species pest complex present at many
periods during the season, the following pest groups can be controlled
with a single application of AZM: a) a petal fall application controls
oriental fruit moth, plum curculio, European apple sawfly and affects
obliquebanded leafrolller; b) an application used during the first
and/or second cover period is directed against the first generation of
codling moth and tufted apple bud moth; c) any of the mid-summer
applications provide excellent control of apple maggot and later
generations of oriental fruit moth; and d) the late summer applications
provide control of codling moth, oriental fruit moth,  apple maggot,
obliquebanded leafroller  and tufted apple moth on late maturing
varieties.  If pesticide resistance is not a factor, such applications
of AZM should provide a very effective management tool for our diverse
pest complex. 

Available alternatives to AZM use on apples.

New compounds: During the last few years, numerous compounds were
registered for use on apples but none of them can provide comparable
pest spectrum activity or efficacy similar to AZM.  Examples of these
new registrations include: acetamiprid and thiacloprid (active against
oriental fruit moth and codling moth, European apple sawfly and plum
curculio but not against leafrollers), methoxyfenozide and novaluron
(effective against leafrollers and internal feeders but not against plum
curculio, European apple sawfly or apple maggot), and indoxacarb which
controls similar spectrum of apple pests but its efficacy is lower than
AZM under the same population pressure.  Other new compounds such as
spinosad, CM granulosis virus or pyriproxyfen provide good control but
for only a very limited number of pests.

Mating disruption (MD) is another very effective method for controlling
oriental fruit moth and codling moth, but the very high initial cost of
the treatments combined with the “only one pest “ activity
characteristic makes this control method practical only in a very
limited number of orchards with very high, problematic populations of
those two pests.  As much as the MD treatments are often the only way to
control pesticide resistant pest populations, it is not an economically
viable component of standard pest management tactics, especially where
multiple pest species need to be controlled at the same time.  

Synthetic pyrethroids (SP), carbamates and other organophosphate
compounds (such as phosmet) are also part of the available assortment of
insecticides registered for fruit pest control.  The low material costs
and relatively wide spectrum of activity makes the SP products very
attractive alternatives for controlling fruit pests traditionally
controlled by AZM.  But multiple research trials over the years as well
as field observations has proven that SP materials in the long run are
very destructive to the natural enemy complexes and the use of compounds
from this group generally results in an increase in populations of
secondary pests (such as mites or scales) that will require additional
applications of insecticides or acaricides.   

Resistance management.  The existence of pesticide resistance to AZM,
phosmet, synthetic pyrethroids and carbamates in some codling moth and
oriental fruit moth populations, effectively eliminates the use of these
alternatives  as the primary groups to replace the current uses of AZM. 
At the same time, it remains an open question about how fast resistance
to the newly registered compounds will develop in the field.  Some
laboratory data suggests that possible cross-resistance already exists
between the old and new chemical groups.  Elimination from the system of
the most effective OP compound (AZM) could result in a lower number of
possible alternatives for a rational rotation.

Efficacy of AZM alternatives.  Although some of the new compounds
provide equal or better control of specific pest species than AZM, none
of them equals AZM in its ability to control various pests with a single
application.  In Pennsylvania and the mid-Atlantic region, where the
apple pest complex is very diverse, a treatment that would be as equally
effective as AZM, would either require a mixture of various compounds or
multiple applications of the same compound, often at much higher rates. 

BEAD scenarios of fruit pests control with complete or partial removal
of AZM from the market:

Scenario 1 suggests replacement of AZM applications with an equal number
of phosmet applications.  In Pennsylvania orchards, a single application
of AZM can likely be replaced with a single application of phosmet, but
with a rate that is at least 2.5-3.0 times higher than AZM (i.e., AZM =
1.5 lb, phosmet = 3.75-4.5 lbs).  Based on a PA local dealer price list
(UAP Northeast) such a substitution would cost $54-75 more per acre (4
applications of Guthion at 1.5 lb/acre at $8.83 per lb replaced with 4
applications of Imidan at 3.75-4.5lbs/acre at $7.15 per lb). 

Under this scenario, it is likely that the quality of fruit will
decrease and actually more pounds of AI will be delivered to the
environment.  

Scenario 2 suggests replacement of AZM applications with one application
of thiacloprid (Calypso(), two applications of novaluron (Rimon() and
one application of acetamiprid (Assail().  The price difference between
these treatments calculated based on the same local dealer price list
will be $89.98 (1.5 lb Guthion( replaced with 3.4 oz of Assail @ $12.60
per oz; 6 oz Calypso @ $6.79/oz and two applications of 20 oz of Rimon @
$1.48 per oz).

Scenario 3 suggests replacement of AZM with CM mating disruption along
with a single rescue treatment of AZM.  Such a scenario would be roughly
$80 more expensive than 4 AZM applications depending on the kind of
mating disruption materials used for the treatment.  Under this scenario
the cost of control of other pests is completely ignored and not
involved in the economic calculation.  The single species MD material
will not control other pest species present in Pennsylvania and
mid-Atlantic orchards. 

The economic analyses of the various presented scenarios for AZM
replacement assume that AZM is only used to control codling moth and
completely ignores the other pests in the fruit system in the eastern
U.S.  It is an unrealistic and unacceptable assumption for the
assessment of possible economic effects of AZM removal from the apple
system.  Other pests, as presented in the earlier part of this
discussion, also need to be controlled.  Thus, additional insecticide
applications will have to be added to the cost analysis.  Such additions
would probably completely change the economic outcomes of the evaluated
scenarios.  Additionally, none of the scenarios take into account the
additional costs related to the increased need for orchard monitoring
and scouting required for proper applications of these new compounds. 
The change in the pesticide assortment is not a simple change in the
names of the compounds, but it is rather a change in how growers need to
think about pest management.  The proper use of the recently registered
chemistries requires a whole new set of knowledge about each single
compound and how each can be used in the most effective manner.

At the same time, although the cost of insecticide programs as part of
the total cost of fruit production represents only a small portion of
all inputs needed to produce good quality fruits, it is still the
portion that growers can still affect and try to reduce as much as
possible.  Under current conditions, it is almost impossible to reduce
any more the cost of labor or energy, other major factors affecting
grower profit.  Often, the cost of pesticide treatments are the only
part of the total production costs that growers can still manipulate. 
And the scenarios presented in the BEAD document are taking away even
this small portion of the constantly shrinking grower profit. 

Summary:

The economic effect of the AZM removal scenarios undervalued the real
economic impact that such removal will have on fruit growers in the
eastern U.S.  The three scenarios, where codling moth is the only pest,
are more specifically applicable to the western U.S. fruit production
areas, and do not represent feasible options for eastern U.S. fruit
growers.  Although, effective alternatives are available for the
majority of pests controlled with previous AZM applications, the high
cost of such replacements would most likely be unacceptable for most
eastern U.S. fruit growers during the foreseeable future.  Results of
our research trials conducted under our recently completed RAMP (Risk
Avoidance and Mitigation Program) project (2005) suggest that effective
control of fruit pests without OP insecticides is possible, but at this
moment such a change is highly costly and resource prohibitive. 
Additionally, more education will be needed for the grower community on
how these newer materials work, how to use them most effectively, and
how to avoid major fruit quality losses.  Even though there are a number
of  available alternatives, if AZM will be removed from the eastern U.S.
fruit market, a long transitional period will be necessary.  The fact
that alternative methods to control the pest complex present in eastern
U.S. orchards are available does not mean that those methods represent a
better alternative choice for fruit growers.  

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