Chosing an appropriate orchard
Selecting a pheromone product
Monitoring codling moth
Managing codling moth
Monitoring non-target pests
Mating disruption as a commercially available
option for codling moth (CM) control was first available in Washington
in 1991. Suppression of CM populations by mating disruption entails
dispensing sex pheromone into orchards in quantities sufficient
to interfere with the normal process of mate location. In 1991
pheromone was applied as the primary control for CM on over 1,500
acres of apples and pears in Washington. The use of mating disruption
has steadily increased over the past four years with about 18,000
acres untreated throughout the state in 1995.
During this five-year period we have evaluated CM mating disruption
in over 200 apple and pear orchards in Washington. Treatments
have included several products or dispenser types application
rates, and combinations of pheromone plus conventional or organic
insecticides. Based on our experience, we have identified six
basic steps in implementing a pheromone-based CM pest management
program in Washington: orchard selection, product selection pheromone
application, CM monitoring, CM management, and non-target arthropod
monitoring and management.
Choosing appropriate orchards Codling
moth mating disruption is influenced by several physical factors,
including orchard topography, size and shape, wind conditions
and canopy structure. The best control is achieved where physical
conditions allow for uniform distribution of pheromone within
the orchard. Thus, sites that are relatively calm and flat are
better candidates for CM mating disruption than sites that experience
frequent winds or have steep slopes. Orchards with large numbers
of missing trees or uneven canopies are considered poor candidates
for CM mating disruption. Using CM mating disruption in a large
contiguous area is considered a better strategy than in small,
individual orchards. However, good control of CM by mating disruption
has been achieved in blocks as small as two acres. The benefits
of applying pheromone uniformly across large contiguous areas
will be addressed by the areawide panel later in the program.
We know that the borders of mating disrupted orchards are especially
vulnerable to CM. Thus, when implementing a pheromone-based CM
control program we recommend that you maximize the amount of orchard
interior relative to orchard edge as illustrated in Figure 1.
If only a single orchard is to be untreated, the best choice is
the one with least amount of border exposed to open areas. Long
narrow orchards are poor choices for mating disruption.
A key factor determining the efficacy of mating disruption is
the initial density of CM within or adjacent to an orchard being
considered a candidate for CM mating disruption. We often refer
to this initial density of CM as the level of CM pressure. Controlling
CM by mating disruption alone becomes more difficult as CM pressure
increases. This is thought to occur because as CM densities increase
the number of successful matings increases, resulting in unacceptable
level of fruit damage. Three criteria each related to CM activity
or controls the previous year, can be used to characterize CM
pressure in an orchard. Codling moth fruit injury from packout
records or field counts provides the best measure of CM pressure
in an orchard. A seasonal count of CM moths captured in pheromone
traps also gives an indication of CM pressure. The number of insecticide
applications required to control CM can also provide an indication
of CM pressure, especially if treatments were based on some measure
of the need for control (e.g. fruit injury or pheromone trap catch).
Using these criteria, we have attempted to characterize orchards
in Washington into four risk classes (very low, low, moderate
and high) with respect to CM mating disruption (Gut and Brunner
1994a). Very low and low risk orchards are the best candidates
for CM mating disruption. Very low risk orchards are characterized
as having CM fruit injury of less than 0.1%. A very low risk orchard
would typically have a seasonal moth catch in pheromone traps
below a treatment threshold and require none or one application
of insecticide for CM control. Low risk orchards are characterized
as having CM fruit injury between 0.1 and 0.4% the previous year.
Moth catches in pheromone traps would usually exceed treatment
threshold, especially in the first flight, necessitating one or
two insecticide treatments to control CM. Mating disruption alone
can provide satisfactory control of CM in very low and low risk
Moderate risk orchards are characterized as having CM fruit injury
between 0.5 and 1.5% the previous year. Moth catches in pheromone
traps exceed treatment threshold more than once, necessitating
two or more applications of insecticides to keep crop loss at
acceptable levels. Mating disruption alone will most likely not
control CM under these conditions. Supplementing mating disruption
with insecticides, primarily during the first CM generation, is
recommended as a standard practice in a CM mating disruption program
in moderate risk orchards.
High risk orchards are characterized as having CM fruit injury
greater than 2.0% the previous year. Moth catches in pheromone
traps would exceed treatment thresholds, necessitating a full
season control program for CM, 3 to 5 insecticide treatments.
Insecticides should be the primary control tactic used for CM
under these circumstances. It may be possible to transition some
high risk orchards to moderate and eventually low risk categories
by using combinations of mating disruption and insecticides. While
this represents an intensive and expensive program for the grower,
it may provide long-term benefits by establishing a more stable
pest management system.
Selecting a pheromone product In
1995, three registered CM mating disruption products ( pheromone
dispenser systems) and at least two experimental products were
used in Washington. The commercially available products were Isomate-C+
(Pacific Biocontrol, Inc.), Checkmate-CM (Consep, Inc.), and NoMate-CM
(Ecogen, Inc.) Three or more products will probably be available
to growers in 1996. What kind of information will help you select
the product that best fit your needs? Manufacturers should be
able to provide you with three critical pieces of information:
the amount of pheromone emitted under different environmental
conditions (i.e. cool, warm and hot temperatures), the longevity
of their product under Washington's growing conditions, and the
level of CM control expected in low and moderate risk orchards
at the rate they recommend.
Codling moth mating disruption products can be classified into two groups based upon characteristics of pheromone release rate and longevity. Group A dispensers are characterized by a moderate rate of pheromone release (i.e. 0.5 to 1.5 mg of CM pheromone per day) and a longevity of 140 to 150 days. Group B dispensers are characterized by a high release rate of pheromone (greater than 2.0 mg of CM pheromone per day) and a longevity of 60-75 days. Strategies for using the two dispenser groups differ. Group A dispensers are intended as a season-long product and are applied one time at the beginning of the first CM flight. Group B dispensers are used in a strategy of multiple applications, usually one against each CM generation.
Two products used most extensively in 1995, Isomate-C+ (Pacific
Biocontrol, Inc.) and Checkmate-CM (Consep, Inc.) illustrate the
relative performances of group A and group B products. The rates
of pheromone loss from field aged dispensers were determined by
residual analysis (Checkmate) or gravimetric analysis (Isomate),
and are plotted in Figure 2. Residual analysis consisted of determining
the amount of pheromone remaining by extraction and gas liquid
chromatography from five dispensers collected every other week.
The gravimetric technique consisted of an initial weighing and
placement in the field of 25 dispensers, followed by collecting,
weighing and replacing them weekly over a period of 140 days.
The Checkmate dispenser released an average of 2.7 to 3.4 mg of
pheromone per day (mg/d) during the first CM generation (Figure
1). Due to this high rate of pheromone loss, the dispenser was
empty after about 60 days in the field. Release of pheromone from
the Checkmate dispenser increased with increasing daily temperatures,
suggesting that dispensers applied for control of the second CM
generation may have released codlemone for less than 60 days,
but data on release rates during this period are not yet available.
The peak release rate from the Isomate dispenser was about half
that observed for the Checkmate dispenser (Figure 1). However,
this dispenser continued to release a substantial amount of pheromone
throughout the season. The amount of CM pheromone released fluctuated
between 0.7 and 1.5 mg/day and depended on weather conditions.
The highest release rates occurred during the hottest part of
the summer, between days 42 and 98 post-application.
Isomate-C+ is designed to provide season-long control of CM under
typical conditions in Washington with a single application, while
Checkmate-CM must be applied at least twice. The recommended application
rates are 400 dispensers per acre (d/a) for Isomate-C+ and 120-160
d/a for Checkmate-CM. In 1995 we directly compared the effectiveness
of both products in six orchards with low to moderate CM pressure.
Isomate-C+ was applied once at 400 d/a, while Checkmate-CM was
applied twice at 160 or 200 d/a. Isomate-C+ provided significantly
better CM control than Checkmate-CM. An average of less than 0.1
% CM fruit injury at harvest was recorded in the Isomate treated
orchards; the highest level of injury was 0.3%. In paired Checkmate-CM
treated orchards CM fruit injury averaged nearly 1%, with a highest
level of 3.0% damage.
Our research strongly indicates that under low to moderate CM
pressure the best strategy for mating disruption is to use a higher
density of dispensers releasing a moderate amount of pheromone,
a strategy best typified by group A products. Our combined experience
during the past 3 years of field research is that a single application
of Isomate-C+ applied at 400 d/a has consistently provided better
CM control than two applications of Checkmate-CM at 120 to 200
d/a. These observations have been supported by results of recent
studies conducted by Dr. Knight, who evaluated the relative effect
on CM mating activity of the number of point sources and the rate
of pheromone emission from each source under controlled conditions.
Six pheromone treatments were compared: 100, 200 or 400 point
sources per acre with each source releasing either 1 mg or 2 mg
of codlemone per day. Each treatment was applied to four 0.3 acre
apple blocks and was evaluated by comparing capture of CM in traps.
Pheromone traps baited with a pair of virgin female moths were
placed in each pheromone treated block and in the four 0.3-acre
non-pheromone treated blocks. Four hundred CM males were released
in each block over a six-week period. Treatment effects were evaluated
by comparing the percentage of traps capturing at least one male
moth. The results are presented in Figure 4. The average percentage
of traps catching a moth was lower in all pheromone treatments
compared to the non-pheromone control, represented by the thick
black line in the figure. Increasing the number of point sources
from 200 to 400 per acre resulted in a very significant reduction
in moth captures. In contrast, there was very little difference
between the 1 and 2 mg release rates at all point source densities.
The most commonly used group A dispenser type, Isomate-C+, has
provided acceptable levels of CM control in low to moderate risk
orchards at 400 d/a, though in the latter a supplemental insecticide
treatment is occasionally required. This product has also provided
acceptable levels of CM control in very low risk orchards at a
reduced rate of 200 to 250 d/a.
The most commonly used group B dispenser type, Checkmate-CM, has
provided acceptable levels of control in very low risk orchards
at the company s recommended treatment rate of 120-160 d/a. However,
in low and especially in moderate risk orchards this recommended
density of dispensers is evidently too low, even with the high
pheromone emission rate, to provide consistent CM control. The
strategy of balancing a lower dispenser density per acre with
a higher pheromone emission rate does not appear to be as good
as maintaining at least a 200 d/a rate with moderate to high pheromone
emission. The Checkmate-CM dispenser system is being engineered
to better suit Washington conditions. Release rates of the newly
engineered dispenser should be determined in the laboratory or
in field-aged tests prior to large scale testing in grower orchards.
Applying the pheromone: To achieve
the best control of CM with mating disruption, dispensers must
be placed high in the tree canopy prior to biofix, the emergence
of the first moths. CM activity and mating is concentrated in
the upper third of the canopy. Weissling and Knight demonstrated
that significant levels of mating occurred in the upper half of
the tree when dispensers were placed at a mid-canopy height, 6
feet (Knight 1995). However, little or no mating occurred in the
tree when dispensers were placed high in the canopy, at 12 feet
(trees were about 14 feet tall). Dispensers should be placed near
foliage to protect them from UV radiation and high temperatures.
Our recommendation is that dispensers be placed within 2 feet
of the top of the tree and in a position shaded by foliage.
Since mating disruption does not provide control once mating has
taken place, its effectiveness is reduced if dispensers are applied
late. To control the first generation of CM, pheromone dispensers
should be applied prior to moth emergence in the spring. First
moths usually emerge about full bloom of "Delicious"
cultivars. Since CM can mate the first or second night after they
emerge, late pheromone applications, such as at petal-fall, can
provide an opportunity for a portion of the population to mate.
Monitoring codling moth: Monitoring
is difficult in orchards treated with mating disruption products
for CM control. A pheromone trap (Pherocon 1CP) baited with a
red septum containing 10 mg of codlemone has been widely adopted
as a component of pheromone-based CM control programs. CM activity
in pheromone treated orchards is more effectively monitored with
this high load lure than with a standard red septum containing
1 mg of codlemone. However, inconsistency of high load lure-baited
pheromone traps to detect "hot spots" in mating disruption
orchards has raised concerns over policies to recommend this monitoring
system as a tool in pheromone-based pest management programs.
We continue to recommend the use of a high load lure-baited pheromone
trap as a tool in mating disrupted orchards but stress three factors
that will greatly reduce the inconsistencies people have experienced
in using it: use a trap for every 2 to 2.5 acres, replace lures
frequently, and place traps high in the canopy. In addition, visual
fruit inspections should be made in conjunction with moth capture
Effective use of a 10 mg red septum in commercial orchards probably
will require changing lures every three weeks during the first
generation CM flight and at least every two weeks during the second
generation CM flight. Our research has demonstrated that moth
captures in traps baited with 10 mg lures decline significantly
after 3-4 weeks in the spring and 2 weeks in the summer. Analysis
of release rates using ion mobility spectrometry (IMS) had indicated
that reduced attractancy of these lures was closely associated
with a decline in the codlemone release rate. In both spring and
summer flights, emission rates dropped sharply during the first
10 days, from about 8 g/hour on day 1 to 3.5 g/hour by day 10.
Emission rates continued to decline in the summer, with only 1.0
g/hour emitted by day 21. In contrast, emission rates above 2.5
g/hour were maintained between day 10 and day 31 of the spring
flight. High summer temperatures appear to increase the rate of
pheromone emission, thus shortening the effective life of the
Codling moth pheromone traps used in conventionally managed orchards
have typically been placed at mid-canopy, or lower because this
position has resulted in good moth capture and they are easier
to maintain than traps placed higher in the canopy. However, when
high load lure-baited pheromone traps are used in mating disrupted
orchards they are more sensitive when placed in the upper part
of the canopy. The performance of traps placed at mid-canopy was
compared with traps placed in the upper canopy in 12 orchards
in the Howard Flat Codling Moth Areawide Management Pilot Project
in 1995. An equal number of traps placed at each height was uniformly
distributed in orchards at a density of 1 trap per 1.25 acres.
Lures were replaced every third week in the first generation and
every other week in the second generation. The "high"
traps were 2 feet higher in the tree canopy than the midcanopy
traps. This positioned them within 1 foot of the height at which
dispensers were placed. The high traps captured about three times
more moths in the first CM generation flight and almost seven
times more moths in the second generation than the mid-canopy
traps. The high traps were a better indicator of CM phenology,
closely tracking the seasonal pattern of moth catch in standard
traps placed in conventional orchards at Howard Flat (Figure 5).
The increased effort required to place traps high in the canopy
may be rewarded by their greater sensitivity and possibly improved
reliability to predict the potential for fruit injury compared
to traps placed at mid-canopy.
Monitoring with pheromone traps is not intended as a stand-alone
method for accessing the effectiveness of CM mating disruption.
Trapping should be used in conjunction with visual inspection
of fruit for CM damage. Inspect fruit on as many trees as possible
and primarily from the upper portion of the canopy, as this is
where the majority of CM fruit injury occurs. Concentrate sampling
first where CM damage is most likely to occur, on orchard borders,
tops of slopes, near bin or prop piles, and in more susceptible
cultivars such as Golden Delicious.
Managing codling moth Mating disruption
alone will not be sufficient for control of CM under certain circumstances.
As discussed previously, supplemental control with insecticides
should be planned in moderate risk orchards. Insecticides should
also be applied if CM-injured fruit injury exceeds 1% at any time
or if pheromone trap catch exceeds a treatment threshold. Using
the monitoring protocols outlined in this article, and summarized
below, the suggested treatment thresholds are a cumulative capture
of 4 or more moths in the first CM generation. The efficiency
of the high load-rate trap declines as the season progresses;
thus, a reduced threshold of 2 moths is suggested for the second
The borders of an orchard require extra attention when implementing
CM mating disruption. Experience has indicated that orchard borders
are often the Achilles heel of this pest control tactic. Two processes
are thought to contribute to the frequent development of border
infestations in mating disrupted orchards, immigration of mated
females from nearby sources and successful mating of CM at orchard
borders. Mating disrupted orchards are especially susceptible
to invasion by CM from external sources. Usually no insecticides
have been applied to control CM, and eggs laid by immigrating
females have a good chance of survival. Pheromone concentrations
on orchard borders are thought to be lower than in the interior,
possibly because of wind sweeping away pheromone. Lower pheromone
concentrations on borders may allow males to locate females more
readily than in the orchard interior, leading to higher fruit
injury in these areas.
Three tactics can be used to protect orchard borders. Additional
pheromone can be applied to border trees or extended into adjacent
orchards if possible. Our experience suggests that this approach
is most effective when initial CM densities are low. In orchards
that routinely sustain CM fruit injury, it is best to treat borders
with insecticides in addition to using higher rates of pheromone
or extending pheromone treatments into the neighboring orchards.
An effective border treatment (insecticides or extra pheromone)
in most orchards would be an area equivalent to 3 or 4 rows around
the orchard perimeter or along the problem border.
Monitoring and managing non-targets:
Mating disruption is a highly specific pest control tactic.
Implementing this tactic for codling moth control, however, will
have a significant impact on non-target arthropods, both pests
and their natural enemies. The abundance of natural enemies is
usually greater in mating disruption than in conventional control
orchards (Gut and Brunner 1994a and b, Knight 1995). This is especially
true where summer insecticides are used in the conventional control
orchards. The potential for biological control of orchard pests
in pheromone treated orchards is discussed by Nick Mills later
in an article in these proceedings.
The specificity of mating disruption can have a negative as well
as positive side. Pests that are kept at non-damaging levels by
treatment with insecticides used to control CM will be released
from all but natural controls in mating disrupted orchards. Natural
controls may provide sufficient control of some non-target pests.
For others, however, the removal of insecticides will mean their
populations will increase, sometimes reaching damaging levels;
and intervention with insecticides or other pest control tactics,
such as augmentative releases of natural enemies, will be necessary.
Leafrollers have consistently become the most important pest in
CM mating disrupted orchards. Two species of leafroller, Pandemis
pyrusana (pandemic leafroller) and Choristoneura rosaceana
(obliquebanded leafroller), have caused high levels of crop
loss, in many cases exceeding that of CM, in pome fruit orchards
using CM mating disruption in Washington (Gut and Brunner 1994a
and b, Knight 1994). The high potential for leafroller populations
to reach damaging levels in the first or second year of transition
to a CM mating disruption program was again made evident when
the majority of Codling Moth Areawide Pilot Project sites reported
a build-up of leafrollers and/or an increased level of fruit injury
at harvest in the first year. The ability to monitor and control
leafroller populations will be crucial to the success of pheromone-based
pest management programs throughout the western region.
The use of azinphosmethyl for CM control has probably been the primary factor preventing many other pest species, such as tent caterpillar, lygus and stinkbugs, from becoming more frequent pests in commercial apple orchards. None of these pests have been reported as a serious problem in mating disruption orchards in Washington during the past five years. However, tent caterpillar colonized three of six mating disruption orchards for three
consecutive years in one of our studies (Gut and Brunner 1994).
The distribution of this pest in orchards was clumped, and developing
populations were effectively controlled by removing infested limbs.
The regular occurrence of this pest suggests the need for more
careful monitoring of rare or sporadic pests in pheromone-treated
Gut, L.J. and J.F. Brunner. 1994a. Pheromone-mediated control
of codling moth in apple orchards. Good Fruit Grower 45(9): 35-48.
Gut, L.J. and J.F. Brunner. 1994b. Implementation of pheromone-based
pest management programs in pear in Washington, USA. Int. Org.
Biol. Control/West Palearctic Reg. Sect. Bull. 17(2): 77-85.
Knight, A.L. 1995. What do we know about the use of sex pheromones?
Good Fruit Grower 46(13): 37-44, 54.