Washington state is located in the very northern portion of the
United States. The state is characterized by having two very
distinct climates, a moist cool climate west of the Cascade Mountains
and a hot dry climate east of the Cascade Mountains.
The majority of commercial fruit production is located in eastern
Washington, primarily associated with major river systems of the
Columbia, Wenatchee, Okanogan and Yakima. Irrigation is critical
to the production of pome and stone fruits with each acre receiving
30 to 40 inches of supplemental water each year.
Codling moth, Cydia pomonella L., is the KEY pest of the
apple in Washington. Control of codling moth has been achieved
with organophosphate insecticides for the past thirty years.
Dr. Stan Hoyt developed integrated mite management which coupled
the biological control of Tetranychid mites, McDaniel spider mite
and the European Red mite, and chemical control of codling moth.
Integrated mite management was possible because Dr. Hoyt discovered
that the predatory mite, Typhlodromus occidentalis, had
developed tolerance to certain organophospate insecticides, especially
azinphosmethyl and phosmet. This program has provided Washington
apple growers a stable and economical pest control program for
many years. Most Washington apple growers have not applied a
specific miticide since the late 1960s.
The use of organophosphates for codling moth control resulted
in the disruption of biological control of a wide range of other
secondary pests, such as aphids, leafhopper and leafminer. These
secondary pests also developed resistance to the most commonly
used insecticides. And as a result additional insecticides were
required to control them.
In the early 1980s the western tentiform leafminer, Phyllonorycter
elmaella, developed populations resistant to most organophosphate
insecticides and many carbamate insecticides. Control can be
achieved with oxamyl (Vydate) but this product often results in
the suppression of predatory mites, a rapid increase in phytophagous
mite populations and the subsequent need to apply specific miticides.
Dr. Bruce Barrett and Dr. Jay Brunner demonstrated that in a majority
of situations a parasitic wasp, Pnigalio flavipes, could
keep leafminer densities below damaging levels if interactions
were allowed to occur. P. flavipes was also shown to be
tolerance of many of the same organophosphate insecticides that
T. occidentalis was tolerant to. The prophilactic use
of oxamyl has declined substantially as growers have learned how
to rely upon P. flavipes for control of leafminer.
In 1989 an average of three insecticides, mostly azinphosmethyl,
were applied to control codling moth. Aphids, mainly Aphid
pomi, the green apple aphid, and leafrollers, Pandemis
pyrusana and Choristoneura rosaceana were the pests
for which the majority of other insecticides were applied.
By 1993 the average number of insecticides applied to control
codling moth had increased to 3.3 per year and the rates had also
increased. Some growers reported levels of codling moth injured
fruit much higher than expected even with 4 to 6 applications
per year. By 1993 leafrollers had become the most important secondary
pest based on insecticide use and they were often identified as
causing more fruit injury than codling moth.
The trend of increasing insecticide applications was very troubling,
especially with reports of codling moth resistant populations
from California. While the protection of fruit is still possible
in California the cost of control programs is high. In Washington
codling moth resistance levels have not been as high as those
detected in California, however, coupled with leafroller resistance
problems Washington growers are facing tremendous challenges in
maintaining a cost-effective stable pest management system.
The development of codling moth populations resistant to many
organophosphate insecticides is troubling but the potential for
this resistance to be expressed as resistance to other insecticides
is even more alarming. Cross-resistance of OP resistant codling
moth to carbamate insecticide was expected since the mode-of-action
is similar. Cross-resistance to insect growth regulators was
not anticipated and these products were expected to provide a
new line of chemical defense against codling moth. However, research
in California has indicated that OP resistant codling moth are
also tolerant of some insect growth regulators. Additionally
in Europe codling moth has developed resistance to insect growth
regulators where they have been used as the primary means of control
for several years.
A scenario that is too often played out in Washington apple orchards
has its basis in the disruption of natural controls by organophosphate
insecticides used to control leafrollers and the resistance to
these products in several pest species. Leafrollers cannot be
controlled with insecticides commonly used to control codling
moth. Thus, growers must rely upon additional insecticides,
such as, chlorpyriphos (Lorsban) or encapsulated methylparathion
(Penncap-M) to achieve adequate control. These insecticides are
highly toxic to P. flavipes, the parasite providing biological
control of leafminer. Released from natural controls leafminer
populations increase and growers are must use oxamyl (Vydate)
to achieve control. Oxamyl is toxic to predatory mites and McDaniel
or European Red mite populations often increase to damaging levels
requiring the use of specific miticides. Few miticides are currently
registered on apple that the potential to select for mite resistant
populations is high under these conditions.
Codling moth and leafroller resistance, higher levels of fruit
injury by insects, concerns for farm worker safety and environmental
stewardship and increased costs of pest control has promoted efforts
to find alternative pest management approaches that would be safe,
stable as well as economical.
Since 1991 there has been as active research program conducted
by Washington State University on the use of pheromones, i.e.
mating disruption, as a control of codling moth. Under normal
conditions the female moth emits a sex pheromone, i.e. calls the
male, which attracts the male from long distance so that mating
The underlying premise of mating disruption is that high concentrations
of the codling moth sex pheromone, codelmone, are dispensed into
the orchard thus preventing male moths from locating females and
mating. The exact mechanism by which this is achieved is not
totally understood but in Washington the approach has worked well.
In the three year study of the transition of apple orchards to
a pheromone-based codling moth control program pheromones (Isomate-C)
provided control as good as the growers standard method (Gut and
Brunner 1994). In one orchard codling moth densities exceeded
levels that could be controlled using pheromone alone.
In experiments conducted in over 200 orchards over the last five
years different pheromone dispensers systems (Isomate-C, Checkmate-CM,
TNO) have been directly compared. In these tests Isomate-C has
provided the most consistent and highest level of codling moth
control. Collective experience indicates that mating disruption
can provide codling moth control when low densities are present
but may require supplemental applications of insecticides under
moderate densities. Under high codling moth densities mating
disruption alone will not provide adequate control of codling
moth and almost always must be supplemented with insecticides.
A consistent problem associated with the use of mating disruption
is the disproportional amount of fruit injury on orchard borders.
Over three years in the study of transitioning of orchards to
a pheromone-based codling moth control program two to three times
more fruit damage was detected on the border compared to the orchard
Leafrollers have been the most important pest problem occurring
in codling moth mating disrupted orchards. In the first or second
year of codling moth mating disruption leafroller populations
have increased to damaging levels. Leafroller may be the Achilles'
heal of codling moth mating disruption. Unless they can be controlled
using "soft" insecticides, such as, Bacillus thuringiensis
(Bt) and insect growth regulators or biological control agents
it will be necessary to use broadspectrum insecticides, greatly
reducing or eliminating most of the economic and environmental
advantages of codling moth mating disruption.
The potential to use mating disruption over large contiguous area
was part of a proposal to the USDA-ARS for management of codling
moth in the western US. The goal of this proposal is to reduce
broad-spectrum insecticide use by 80% in five years by demonstrating
the utility of implementing mating disruption as a control for
Five implementation sites in three western states (Washington-3,
Oregon-1, California-1) were selected. Sites in California and
Oregon are primarily pear production areas while Washington sites
were primarily apple areas. The size of the pheromone treated
area at each site varied as did the number of growers and crop
One site established in Washington was at the Howard Flat growing
area near Chelan. This is a fairly isolated production area of
about 1,200 acres. Apple is the predominant fruit crop produced
though pear and cherry are also grown. Thirty-six (36) growers
farm at Howard Flat and they pack fruit at four cooperative warehouses
and 16 crop consultants provide advice on pest control and horticultural
In 1994 a grass-roots effort of crop consultants and interested
growers attempted to initiate an areawide codling moth control
program. Only about 300 acres were treated with pheromone and
results were mixed. Grower education meetings were held to explain
how best to use mating disruption and to show why higher than
expected injury occurred in some orchards.
This did not deter interest in the approach and in the fall of
1994 meetings were held to explore the idea of organizing the
entire Howard Flat area as an Codling moth Areawide Management
Project (CAMP). Growers and crop consultants established a CAMP
Board consisting of five consultants and three growers. In cooperation
with a Howard Flat Technical Advisory Committee a proposal was
submitted to the USDA-ARS Fruit Research Laboratory in Yakima
to be a site to receive funding to help implement an areawide
codling moth management pilot project in the western US.
The proposal was funded and $105,000 was allotted to Howard Flat
in 1995. The funding provided a salary for a full-time coordinator,
supplies, and operations. Over half of the funding, $55,000,
was used to subsidize the cost of the pheromone to the growers
at a rate of $50 per acre. The cost of the pheromone used, Isomate-C+,
was $110 per acre so the grower was paying out of pocket $60 per
acre, this in addition to insecticides that he would need to apply.
Organization meetings with growers were held prior to the season
and only two of 36 decided not to participate in the project.
A total of 1,135 acres were treated with Isomate-C+ in April.
Some growers applied the pheromone dispensers themselves while
about half decided to pay the project $15 per acre to apply the
dispensers. Pheromone was attached to large plastic clips prior
to the time of hanging. It was placed high in the tree canopy,
within the upper two feet, using long poles, avoiding the need
for ladders and greatly speeding the application.
To monitor codling moth activity in orchards pheromone traps,
(Pherocon 1CP, Trécé Inc) and a high load lure (red
septum with 10 mg of codelmone) were place in every 2 to 2.5 acres,
a total of 448 traps were used. Traps were place at mid-canopy,
ca. 8 feet average, monitored weekly and lures changed every three
weeks (first flight) or two weeks (second flight).
The use of high load lures to monitor codling moth activity in
mating disruption orchards and the need to apply pheromone high
in the tree canopy has been established by research conducted
by Larry Gut and Jay Brunner (WSU) and Alan Knight (USDA-ARS),
Leafroller moths were also monitored at Howard Flat. Fifty-six
traps of P. pyrusana and C. rosaceana were distributed
uniformly throughout the area and checked weekly. Other pests
monitored in 15 pre-selected blocks included aphids, leafhopper,
mites, leafminer and the mullen plant bug, Campylomma verbasci.
Common natural enemies associated with these pests were also
monitored. The intent of monitoring this group of secondary pests
and their natural enemies was to follow changes in their populations
and compare these to similar pest and natural enemy populations
in conventional orchards within the area but not at Howard Flat.
Codling moth monitoring indicated high populations in many orchards.
More than 3,000 moths were captured in 270 of the 448 traps (60%)
during the first 3 weeks of monitoring. The high level of codling
moth pressure in many orchards was anticipated based on fruit
injury reports from 1994 and histories of pest problems in certain
areas on Howard Flat. All growers were advised by crop consultants
to apply a well-timed first cover spray for codling moth control;
this was in addition to suppression expected by the pheromone.
Following the beginning of the first cover applications, codling
moth captures in traps dropped dramatically. Twenty-one percent
of traps captured zero moths during the first codling moth generation,
and 57% of the traps captured four or fewer moths, a level suggested
as a treatment threshold in orchards using mating disruption.
The dramatic drop in moth captures on Howard Flat following the
initiation of codling moth cover sprays suggested that moths in
the region were not resistant to organophosphate insecticides.
Bioassays were conducted to determine the level of resistance
in codling moth adults at four separate locations within Howard
Flat and at the Tree Fruit Research and Extension Center in Wenatchee.
Dose-mortality curves generated from the bioassays indicated
that only a low level of resistance was present within codling
moth populations at Howard Flat.
Capture of codling moth was much lower during the second generation.
Sixty-five percent of traps captured zero moths during the first
codling moth generation, and 93% of the traps captured four or
fewer moths. Cover sprays to control codling moth were planned
in high pressure orchards during the second generation. However,
additional controls were not applied to most pheromone treated
blocks because of the high level of fruit damage caused by a hailstorm
that hit the region on July 9.
Approximately 70% of the orchards on Howard Flat were affected
in some way by the hailstorm, and in many orchards such a high
percentage of fruit was damaged that it could only be harvested
for the processing market. Mating disruption alone provided adequate
codling moth suppression in the second generation for most orchards,
even those which were damaged by hail.
In 1994, 5,006 codling moths were captured in 155 traps at Howard
Flat, an average of 32.3 moths per trap. In 1995, 3,929 codling
moths were captured in 448 traps, an average of 8.8 per trap.
These data cannot be used to compare years but serve to show
the high pressure from codling moth on Howard Flat prior to the
initiation of the project.
Fruit injury by codling moth was determined following the first
generation in selected blocks by visually examining 1,000 fruits
per block. Fruit injury by codling moth was between 0 and 0.3%.
The combination of the pheromone and insecticide applied first
generation was very effective.
Bin samples were taken to assess codling moth injury to fruit
from as many blocks as possible during the harvest period. A
minimum of 25 bins per variety, 100 fruit per bin, was monitored
from each block. A total of 1,726 bins (172,600 fruits) was sampled
from 46 blocks. The overall average fruit injury in blocks from
Howard Flat sampled was 0.55%. There was more damage in Golden
Delicious (0.9%) compared to Delicious (0.4%). The highest levels
of fruit damage occurred in blocks near the airport where traditionally
there had been high pressure from codling moth. Without hail damage,
some growers would have responded to pheromone trap captures in
their blocks and applied a control spray in the second codling
Fruit packout records from Howard Flat orchards indicated an average
level of codling moth fruit injury of 0.8%, this despite the application
of an average of 2.87 insecticides specifically to control codling
moth. In 1995 the average number of insecticides applied for
codling moth control was 1.7.
Capture of P. pyrusana was concentrated in the northwest
section of Howard Flat, most in just a few traps. In the second
flight P. pyrusana moths were again concentrated in the
northern portion of Howard Flat but higher counts were recorded
in more orchards. Capture of C. rosaceana was lower than
that of P. pyrusana in the first flight period but was
again concentrated more in the northern section of Howard Flat.
There was an increase in the number of traps capturing C.
rosaceana in the second flight. Howard Flat has not had a
historical problem with leafrollers, however, reductions in organophosphate
insecticides because of mating disruption of codling moth coupled
with the level of moth captures in 1995 should be sufficient warning
to growers. Leafrollers should be monitored carefully and the
need for controls in 1996 anticipated.
Monitoring aphids, leafminer, leafhoppers, leafroller and the
mullen plant bug in 15 selected blocks revealed very little about
these insects or their natural enemies. Aphids, leafminer, leafhopper
and mite densities were very low throughout the summer as were
natural enemies commonly associated with them. Leafroller densities
were also low in all blocks except one that was not treated with
pheromone but managed with conventional insecticides. It is too
early in the project to determine how much influence the use of
pheromones had on reducing problems with secondary pests in most
The potential of using codling moth mating disruption to radically
alter pest management in apple orchards of Washington and other
western states is only just beginning to by understood. It appears
to hold great promise for reducing reliance on broadspectrum insecticides
as the first line of defense against codling moth and other pests.
A pheromone-based pest management system for apple and pear would
allow growers to take greater advantage of biological controls
for many pests, rely on "soft" chemical controls to
suppress pests when needed and reserve the BIG weapons, the fast
acting broadspectrum insecticides to stop pests that cannot be
controlled with other means. This should lead to a stable, safe,
environmentally friendly and hopefully economical pest management