Temperature, irradiation and delivery as factors affecting spring-time flight activity and recapture of mass-reared male codling moths released by the Okanagan-Kootenay sterile insect programme

2006·8.8 MB·English

by  Gary J R Judd

J. Entomol. Soc. Brit.Columbia 103,December2006 19
Temperature, irradiation and delivery as factors
affecting spring-time flight activity and recapture
of mass-reared male codling moths released by the
Okanagan-Kootenay sterile insect programme
GARY J.R. JUDD^ ^ and MARK G.T. GARDINER^
ABSTRACT
Laboratory flight-tunnel and field mark-release-recapture experiments were conducted
to compare pheromone response, flight activity and recapture of wild codling moths,
Cydiapomonella (L.), with codling moths mass-rearedby the Okanagan-Kootenay Ster-
ile Insect Release Programme. These experiments were designed to identify factors that
may contribute to poorpheromone trap catches ofsterile moths in the spring. Irradiation
(250 Gy) hadno influence on catches ofmass-reared moths inpheromone traps at spring
(16 °C) or summer temperatures (25 °C) in flight-tunnel assays. In field experiments
however, recapture ofmass-reared and wild moths in pheromone traps was significantly
reduced after irradiation, suggesting effects of irradiation were modified by additional
factors acting in the field. Catches ofmass-reared moths in flight-tunnel assays showed
a nonlinear increase with increasing temperature. There was no evidence that mass-
reared moths were less responsive to pheromone at low temperatures than wild moths.
Basedonx-intercepts oflinearregressions ofpercent catch v^. temperature (15-25 '^C),
flight-temperature thresholds for mass-reared (14.7 °C) and wild moths (15.4 °C) were
similar in flight-tunnel assays. Irradiated moths carried for 4 h on all-terrain vehicles
used for delivering sterile moths were less responsive to pheromone lures in subsequent
flight-tunnel assays than moths that spent no time on these vehicles, but only when
flown at spring-like temperatures (16 °C). In field tests, moths released on the ground
were caught significantly less often than moths released within the tree canopy and
negative effects ofground release appeared greaterwhen made in spring compared with
autumn.
KeyWords: Codling moth, sterile insect technique, sterile:wildratios, flight-
temperature thresholds, flighttunnel tests, mark-recapturetests
INTRODUCTION
The Okanagan-Kootenay Sterile Insect tion (open-ended). The objective ofphase 2
Release (SIR) Programme was initiated in was to deliver sufficient sterile moths each
1992 to eradicate codling moth, Cydia week to maintain ratios ofca. 40 sterile (S)
pomonella (L.) (Lepidoptera: Tortricidae), to 1 wild (W) male moth in pheromone trap
from montane fruit-growing regions in Brit- catches for the entire season. This 40:1 ratio
ish Columbia (BC). Dyck et al. (1993) de- was deemed necessary ifsterile moths were
signed this SIR Programme with three going to reduce wild populations to near
phases: (1) pre-release sanitation (two extinction in three years (Proverbs et al.
years), (2) sterile moth release (three years), 1982, Dycketal. 1993).
and (3) surveillance monitoring and protec- Following a pre-release sanitation pro-
'Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Hwy 97, Summerland,
BritishColumbia, Canada,VOH IZO
^Authortowhomcorrespondence shouldbesent(email:[email protected])
20 J.Entomol. Soc.Brit.Columbia 103,December2006
gramme that extended from Osoyoos to activity of sterile moths in relation to tem-
Summerland and included the Creston and perature has been discussed, catches in
Similkameen Valleys (49'' 34' N Latitude - pheromone traps havebeen usedto measure
W
119'' 39' Longitude), sterile moths were this activity (Hutt 1979, Rogers and Winks
released area-wide in May 1994. SIR Pro- 1993, Bloem et al. 1998, 1999, 2004, Judd
gramme trapping data (1994 - 2004) indi- et al. 2004). Interpreting these data is diffi-
cates that since 1994, S:W ratios have cultbecause several factors are confounded.
rarely reached 40:1 in the spring, often fail- For example, mass-reared codling moths
ing to reach 10:1, whereas target ratios may fly poorly at cool temperatures, but it
were usually achieved in the summer is equally plausible that mass-reared moths
(Thistlewood et al. 2004). Consistently low have undergone behavioural changes re-
S:W ratios in the spring have delayed popu- lated to pheromone communication that are
lation suppression, made supplementary only expressed under cool spring tempera-
controls necessary and increased pro- tures. Also, as none of the above studies
gramme costs (Thistlewood and Judd 2003, measured the relative effects of irradiation
Judd et al. 2004, Judd and Gardiner 2005). or ground release on trap catches, or in-
In recent years the focus ofthe programme cluded similarly-treated wild moths, any
has changed from eradication to manage- adverse effects of mass-rearing can not be
ment, but because sterile moths continue to separated from interacting effects ofirradia-
be the primary control tactic in spring, im- tion, handling andrelease techniques.
provements in programme delivery are Our objective was to identify factors
needed to make it economically sustainable that might contribute to poor activity of
(Dendy et al. 2001). Understanding the sterile moths in the spring in an effort to
factors that contribute to inactivity ofsterile take corrective action to improve S:W ra-
moths in the spring may lead to corrective tios in the operational SIR Programme. We
action and improve the economics of the undertook studies to specifically examine
programme. the effect ofair temperature on pheromone
Bloem and Bloem (1996) hypothesized response ofmass-reared codling moths rela-
that cool weather was largely responsible tive to wild moths and to determine iftem-
for suboptimal S:W ratios in the spring, perature modified any effects ofirradiation
implying mass-reared moths fly poorly at and handling. In this study we use field
low temperatures. Although normal sea- mark-release-recapture tests to assess activ-
sonal increases in temperature and recap- ity of codling moths (Bloem et al. 1998),
ture rates of sterile males are correlated, a but also use a laboratory flight tunnel be-
clear cause and effect relationship between cause we wanted to isolate effects of tem-
temperature and flight activity of sterile perature on activity and pheromone re-
moths has never been demonstrated (Judd sponse without the confounding effects that
et al. 2004). In nearly all studies where the field experiments impose.
MATERIALS AND METHODS
Test insects. Wild codling moths used at the Pacific Agri-Food Research Centre
in these experiments were collected as dia- (PARC) in Summerland. They were held
pausing larvae from several organic apple there in plastic garbage bags until March of
orchards in the Similkameen Valley. Corru- the following year, when they were placed
gated cardboard bands were wrapped and in a 0.5 "^C growth chamber in total dark-
stapled to trunks of apple trees in July to ness. Wild larvae were brought out ofcold
capture overwintering, diapausing fifth in- storage as needed for experiments and set
star larvae (Judd et al. 1997). Bands were up in emergence cages held in environ-
removed from orchards in early October mental chambers at 27 °C under a 16:8 h
and transferred to an outdoor screen house Light:Dark (L:D)photoregime.
J. Entomol. Soc. Brit.Columbia 103,December2006 21
All mass-reared codling moths used in ery to field cold-storage units, orafterbeing
these experiments were produced by the carried by drivers on moth-release vehicles
Okanagan-Kootenay rearing facility in for4 h.
Osoyoos, BC as described by Bloem and Flight-tunnel procedures. A pushing-
Bloem (2000). For experiments requiring type flight tunnel described in detail by
non-irradiated moths, trays ofartificial diet Judd etal. (2005) was used to assess behav-
(Brinton et al 1969) containing mature ioural responsiveness of male codling
larvae were provided by the Osoyoos rear- moths to sex pheromone sources in clean
ing facility as needed and transferred to an air. An air conditioning unit attached to the
environmental chamber at PARC where air intake vent at the upwind end of the
T
they were held at 27 under a 16:8 h L:D tunnel allowed us to achieve flight tempera-
photoregime. Mature pupae were removed tures of ca. 10 - 25 °C in the tunnel. De-
from the diet, sexed andplaced individually tailed description of moth handling proce-
in 30 ml plastic cups provided with wet dures and experimental protocols for flight-
cotton wicks until moths eclosed. Male and tunnel assays are described by Judd et al.
female moths from all sources were isolated (2005). Pheromone lures used in flight-
in separate environmental chambers main- tunnel experiments were made from red
tained at 27 ''C and 65% relative humidity rubber septa (Aldrich Chemical Company
with 16:8 h L:D photoregime before testing. Inc., Milwaukee, Wisconsin) loaded with
Irradiated, mass-reared moths were ob- 200 |Lil of dichloromethane containing 10
tained from the SIR Programme's Osoyoos jug of the codling moth sex pheromone
rearing facility. Moths were collected in (£',£)-8,I0-dodecadien-l-ol, known as
aduh emergence rooms (27 °C) after flying codlemone (99% isomeric and chemical
UV
out ofdiet trays towards lights located purity, Shin-etsu, Fine Chemicals Division,
on the ceiling. Vacuum hoods adjacent to Tokyo). Septa were air dried for ca. 18 h at
UV lights drew moths through pipes into a 23 °C in a fume hood and stored in sealed
collection room maintained at 2 °C. Chilled jars at 0 °C until used.
moths were then packaged by weight into Mark-release-recapture techniques.
plastic petri dishes in which they were irra- Before each field release and some labora-
diated. Moths were sterilized by exposure tory assays, moths were chilled for 10 min
to 250 Gy (11.5 - 13.2 Gy min"') ofgamma in a cold room (0.5 ""C) and dusted lightly
radiation from a Cobalt^^ source with Day-Glo"^ Daylight Fluorescent Pow-
(Gammacell 220, Nordion, Canada). After ders (Switzer Brothers Inc., Cleveland,
irradiation petri dishes were loaded into a Ohio, USA). Different coloured powders
refrigerated trailer (4 °C) and trucked to were used to distinguish groups of moths
area drop-off points. There they were treated, handled or released differently.
placed either in temporary storage facilities Marked moths were placed in plastic petri
(4 °C) awaiting pickup by delivery drivers, dishes or 60 ml plastic cups and transported
or directly into coolers (6-8 °C) on the to field sites in ice chests. Dishes or cups
backofall-terrain vehicles (ATVs) outfitted were opened in the field and moths took
with moth-dispensing units (McMechan flight undertheirown capacity. Pherocon 1-
and Proverbs 1972). Irradiated moths des- CP style, sticky, wing traps (Phero Tech
tined for release were moved from ATV Inc., Delta, BC), baited with similar 10 |Lig
coolers and placed in a small hopper on the lures as used in flight-tunnel experiments,
front of the ATV, where a small fan unit were used to recapture moths. The 10 |ug
dispensed moths by gently blowing them lure load was chosen because it releases
onto the ground beneath trees. In some codlemone at a rate similar to an individual
cases sterile moths spent up to 4 h in the female codling moth (Backman 1997) and
release-vehicle cooler before being dis- has the advantage ofbeing both attractive in
pensed at the end ofa delivery route. Moths the field, at least for short periods of time,
used in this study were collected afterdeliv- and the flight tunnel, the latter ofwhich is
22 J. Entomol. Soc.Brit.Columbia 103,December2006
not true of standard 1 mg field monitoring recorded. Temperature was adjusted and the
lures. When experiments were completed procedure repeated until catch at all four
traps were returned to PARC where expo- temperatures was evaluated on a given day.
sure to UV light revealed the fluorescent Percentage catch for each moth type was
dusts and moths were counted. plotted against temperature. Linear regres-
Flight Tunnel Tests sion (SigmaStat®) was used to estimate the
Experiment 1: effects of irradiation lower threshold temperatures for phero-
on pheromone response. Responses of mone-mediated flight based on the x-
irradiated (250 Gy) and non-irradiated, intercepts of these lines. A ^-test was used
mass-reared codling moths to pheromone to compare slopes of regression lines (Zar
lures in flight-tunnel experiments were as- 1984).
sessed at 16 and 25 "C, temperatures typical To verify the lower-temperature flight
of dusk in the spring and summer respec- threshold for mass-reared moths we con-
tively. On each of seven flight days, ducted a set of six additional flights with
uniquely-marked (as above) groups of 9 - groups of 17 - 45 mass-reared moths at 13,
10 irradiated or non-irradiated moths were 14, 14.5, and 15 °C. A one-way ANOVA
flown in random order at one of the two and Student-Newman-Keuls' multiple com-
randomly assigned temperatures. The per- parisons test were used to compare mean (n
centage of moths caught in a pheromone- = 6) percentage capture at each of these
baited trap within a 30 min period was re- temperatures (SigmaStat®).
corded, then the other group was flown, Experiment 3: effects of handling
after which the temperature was changed time in moth release vehicles. Irradiated
and the process repeated. Moth catches codling moths were collected at two differ-
were expressed as proportions (p) and ent points in the moth distribution process
transformed using arcsine Vp. Mean recap- used by the SIR Programme. Moths were
ture rates for each treatment combination obtained at noon on each of 10 days after
were calculated and compared using a two- they were delivered by a refrigerated truck
way (flight temperature, radiation treat- and placed in a storage refrigerator at a
ment) analysis of variance (ANOVA) with drop-off depot in Summerland. One petri
a temperature x irradiation interaction term dish ofirradiated moths was removed from
in the model. Significance ofeach factor in the storage fridge and labelled ATV - 0 - h.
the model was tested using an F-test. All A second petri dish labelled ATV - 4 - h
statistical analyses were performed with an was removed from a cooler on the back of
a value of0.05 using SigmaStat* (Version an ATV which had just returned after four
3.0, SYSTAT Software Inc., Richmond, hours of field deliveries. Labelled petri
CA). dishes were returned to PARC where moths
Experiment 2: effects of air tempera- were sexed and counted in a 0.5 °C cold
ture on pheromone response. Pheromone room. Fifty males were placed in each of
responses of non-irradiated, mass-reared several 11.4 L plastic buckets and held
moths and apple-reared wild moths emerg- overnight at 27 °C in an environmental
ing from diapause, were compared in the chamber under a 16:8 L:D photoregime.
flight tunnel at 15.5, 17.5, 19 and 25 °C The following day moths were chilled for
following a randomized block design. On 10 min at 0.5 ""C, placed individually into
each of 5 flight days (blocks), uniquely- release cages described by Judd et al.
marked groups of 11 - 15 mass-reared and (2005) and transferred to the flight-tunnel
11-15 wild males were flown simultane- room 15 min before scotophase. Following
ously from the same release cage described a randomized block design, on each of 10
by Judd et al. (2005) at one randomly as- flight days (blocks), moths from each treat-
signed temperature. The percentages of ment group (ATV- 0 h and ATV- 4 h) were
each moth type caught in a pheromone- flown individually in random order at one
baited trap within a 30 min test period were of two randomly assigned temperatures
0
J. Entomol. Soc. Brit. Columbia 103,Dhcembbr2006 23
typical of spring (16 ^C) and summer (25 m tree x 4.6 m row spacing and an average
''C); one moth from each of the two han- tree height of 3 m. Four wing traps, each
dling times was flown in every two flights. loaded with 10 |Lig ofcodlemone, were hung
Each moth was placed downwind from a 1 ca. 1.5 - 2 m above ground in the central
|Lig pheromone lure and given 2 min to fly tree of this release area. One trap was
upwind and make contact with the lure. placed in each cardinal sector ofthe central
After flying 7-18 moths from each treat- tree. After one week, traps were returned to
ment group the temperature was reset and PARC and marked moths caught were iden-
the process repeated. tified under UV light. Catches ofeach moth
On a given test day the percentages of treatment group in all four traps within a
each moth type making contact with the given orchard (replicate) were summed and
pheromone lure at each temperature were used to calculate the percentage recapture.
calculated. Percentage data were trans- This entire procedure was repeated in four
formed by arcsine V/? and mean rates of independently replicated releases in differ-
source contact at each temperature, for each ent orchards. Percentage recapture data
handling treatment, were compared using a were transformed by arcsine V/? and ana-
two-way (flight temperature, moth handling lyzed using a two-way (moth type, irradia-
treatment) ANOVA with a temperature x tion treatment) ANOVA model containing a
handling interaction term in the model. Sig- moth type x irradiation treatment interac-
nificance of each factor in the model was tion term. Significance ofeach factor in the
testedusing an F-test. model was testedusing an F-test.
Field Tests Experiments 5-7: effects of ground
Experiment 4: effects of irradiation release on moth recapture. Experiments 5
on pheromone trap catches of mass- and 6 were preliminary tests designed to
reared and wild moths in the field. A compare the rates of recapture of moths
mark-release-recapture field experiment released within the tree canopy with those
was conducted in September to assess the released on the ground beneath the same
effects ofirradiation onrates ofmoth recap- trees. Within-canopy release was used to
ture in pheromone traps. Mass-reared cod- simulate the location that recently-emerged
ling moths (from trays of diet provided by wild moths might likely be found, and
the Osoyoos facility) and diapausing wild ground release was used to simulate the
moths emerged in our laboratory as de- location that sterile moths were delivered
scribed in the test insect section above. by the SIR Programme. Uniquely-marked,
Two- to three-day-old moths were trans- irradiated, mass-reared moths were used for
ported to the Osoyoos rearing facility, these experiments. Paired independent re-
where one halfofeach moth type was irra- leases were conducted during September in
diated with 250 Gy and the other half re- two separate orchards and each orchard
mained non-irradiated to serve as a control release was analyzed as a separate non-
group. This procedure provided four moth replicated experiment (5 and 6). Moths
m
treatment groups: irradiated and non- were released and recaptured in 32 x 32
irradiated, mass-reared and wild moths, square release areas exactly as described in
respectively. After irradiation, moths were experiment 4, with the exception that an
returned to PARC, chilled (0.5 T) and each additional set ofadult moth release devices
of the four moth treatment groups was was placed on bare soil at the base of the
uniquely marked as before. One moth re- four comer trees in each release area. Any
lease device, as described by Judd et al. effects of moisture in these experiments
(2006a), and containing 24 moths of one were minimal because both releases were
treatment was hung within the canopy of made during September in an absence of
each ofthe four comer trees in a 32 x 32 m any irrigation and moths were released in
square release area located near the centre early afternoon when dew had evaporated.
ofa mixed-variety apple orchard having a 3 Direct moth contact with the ground was
24 J.Entomol. Soc.Brit.Columbia 103,December2006
minimized by moths flying from release recapture procedure was repeated on four
devices undertheirownpower. Within each different occasions: (I) 12 - 16 May, (II) 19
orchard (experiment), the paired propor- - 23 May, (III) 26 - 30 May, and (IV) 2 - 6
tions of ground- (p ground) or canopy- June. In total 16 independent releases and
released moths (p canopy) recaptured out of recaptures were made. Within each five-day
the 128 moths released at each ofthese lo- release-recapture test period (I - IV), 128 -
cations within each orchard, were compared 200 uniquely-marked moths were released
using z-tests on two binomial proportions from within the canopy offour trees and on
(Zar 1984). bare dry soil beneath each ofthese trees in
In experiment 7 the effect of release each orchard. Percentage recapture of
location on recapture of moths was exam- moths from each release location (canopy
ined again but under spring temperature vs. ground), within each orchard and time
conditions in a series of replicated tests. interval was transformed by arcsine Vp.
Four independent but simultaneous moth Recapture data for each time period (I - IV)
releases (replicates) were made in four were analysed separately because each time
similar release areas and moths were recap- period represented an independent set of
tured in each area as described in experi- releases rather than a repeated measure on
ments 5 and 6. The experimental sequence one set ofreleases. Within each time period
was to release moths during afternoons of mean recaptures from each release location
days 1 - 3 and trap during nights 3 and 4. (canopy vs. ground) across the four release
Traps were removed the morning of day 5 orchards (replicates) were calculated and
and returned to the laboratory to identify comparedusing apaired /-test.
and count moths. The above mark-release-
RESULTS
Flight-Tunnel Tests nonlinear, but within the range of 15.5 and
Experiment 1: effects of irradiation 19 °C it appears linear. Nonlinearity at
on pheromone response. Irradiation (250 higher temperatures is probably an experi-
Gy) ofmass-reared moths had no influence mental artifact because catches can not be
(Fi,24 ^ 0.13, P = 0.72) on their response to greater than 100% and maximum response
pheromone lures in flight-tunnel assays appears to have been reached near 19 °C
(Fig. 1). There was no interaction between (Fig. 2A). Nonlinearity at lower tempera-
temperature and irradiation treatment (F],24 tures is an indication of a lower-
= 0.10, P = 0.754) indicating the effects of temperature threshold for pheromone-
irradiation were the same at temperatures mediated flight. This lower-temperature
typical of spring (16 °C) and summer (25 threshold seems most relevant within the
°C) (Fig. 1). Temperature had a highly sig- context of comparing pheromone-mediated
nificant effect (F],24 = 102.69, P < 0.001) flight of mass-reared and wild codling
on catches of mass-reared moths in this moths and S:W trap-catchratios.
experiment (Fig. 1) and its effects were Catches ofwild codling moths in flight-
studied in more detail in subsequent experi- tunnel assays were lower than mass-reared
ments. moths at every temperature tested (Fig. 2B).
Experiment 2: effects of air tempera- No wild moths were caught at 15 °C and
ture on pheromone response. Forillustra- only 58% were caught at 25 °C (Fig. 2B),
tive purposes the percentages of mass- compared with 85% catch of mass-reared
reared moths caught in two separate tests moths (Fig. 2A). Linear regression was
were plotted against the complete range of used to compare the temperature response
temperatures evaluated in these tests (Fig. function ofthe two populations ofmoths in
2A). This plot suggests that the pheromone flight-tunnel assays (Fig. 2B). The slopes
response x temperature function of mass- (20.3 SIR vs. 5.6 Wild) ofthese regression
=
reared moths between 13 and 25 ""C is lines were significantly different (/-test, t
J. Entomol. Soc. Brit.Columbia 103,Deckmber2006 25
Non-Irradiated
]
Flighttemperature °C
Figure 1. Mean + S.E. percentages ofirradiated (250 Gy) and non-irradiated, mass-reared male
codling moths caught in a synthetic pheromone-baited trap (red septum with 10 |uig load) in 30-
min flight-tunnel tests conducted at temperatures typical ofspring (16 °C) and summer (25 ""C).
Two-way ANOVA indicates a significant temperature effect (Fi.24 = 102.69, P < 0.001) but no
significantradiation effect (Fi,24= 0.13, /*= 0.72).
7.05, df - 26, P < 0.001). Similar x- time on the ATV (Fig. 3). A statistical com-
intercepts suggest the lower-temperature parison isolating these two treatments found
thresholds for pheromone-mediated flight a significant reduction (two sample Mest, t
of wild (15.4 ''C) and mass-reared males - 2.62, df = 18, P = 0.022) as a result of
(14.7 T) are similar (Fig. 2B) but no statis- being carried on the ATV that was not de-
tical test was made. The lower threshold for tected in moths flown at 25 ""C (t - 0.67, df
mass-reared moths was substantiatedby our = 18, P= 0.95) (Fig. 3).
separate comparison of the percentages of Field Tests
mass-reared moths caught at 13, 14, 14.5 Experiment 4: effects of irradiation
and 15 °C. In this experiment there was a on pheromone trap catches of mass-
significant difference in catches at 15 ""C reared and wild moths in the field. Irra-
(16.3 ± 3.7%) and all other temperatures diation significantly (F] g = 15.53, P =
(F3,i8 = 9.87, P < 0.001), but not between 0.004) reduced recapture of both mass-
X
14.5 (5.7 ± 1.5%) and all lower tempera- reared and wild codling moths relative to
tures (SNKtest, P< 0.05). non-irradiated moths in a field test con-
Experiment 3: effects of tiandling ducted in late September (Fig. 4). Overall
time in moth release vehicles. Tests ex- catches of mass-reared and wild moths in
amining the pheromone response of mass- pheromone traps were not significantly
reared moths at different temperatures after different (F,,8 = 0.46, P = 0.517). The ef-
being carried on an ATV delivery vehicle fects of irradiation were independent of
revealed a significant temperature effect moth type (Fi.g = 0.02, P = 0.88). Irradi-
(Fi,36 = 87.44, P < 0.001), but no signifi- ated, mass-reared moths were about 1.5x
cant handling time effects (Fj 35 = 0.33, P = less responsive to pheromone traps in this
0.57) and no significant interaction between field test than were the non-irradiated wild
temperature and handling times (Fj 36 ^ moths they compete with in a sterile insect
0.98,P- 0.33). However, when flown at 16 programme (Fig. 4).
°C, the percentage ofmoths making contact Experiments 5-7: effects of moth
with a pheromone lure after experiencing 4 release location on recapture. In two
h on an ATV was clearly depressed relative separate non-replicated releases conducted
to contacts made by moths that spent no in mid September, irradiated, mass-reared
26 J.Entomol. Soc. Brit.Columbia 103,December2006
-
80
O)
3 • /
cou
60
CO
JO.
SIR moths
40 y = 87.53 / (1 + exp (-(x-16.77) / 1.08))"
20
t •
13
B
COD
80
CO SIR moths
o y = 20.3x-298.7
E
^ 60
40
LU Wildmoths
CO
+1 y = 5.6x-86.5
20 -
CD
CU
J I / I
13 15 17 19 21 23 25
X
Flight temperature
Figure 2. (A)Composite scatterplot ofpercentages ofnon-irradiated, mass-rearedmale codling
moths (SIR moths) caught in a synthetic pheromone-baited trap (red septum with 10 |ig load) in
separate 30-min flight-tunnel tests conducted at different temperatures (13 - 25 °C). Dottedcurve
represents best-fit nonlinear regression line. (B) Plot of mean ± S.E. percentages of non-
irradiated, mass-reared (SIR moths) and wild codling moths caught over temperature ranges of
15.5 - 19°C for SIRmoths and 15.5 - 25 °C forwildmoths. Solid lines are best-fit least-squares
linear regression lines for relationship between percentage catch and temperature (ANOVA n =
15; df=1, 13; P < 0.001 for each line). Slopes ofregression lines are significantly different (/-
test, t= 7.05, df= 26,P< 0.001).
moths released on the ground were recap- releases made during four weekly test peri-
tured (p ground) significantly less often ods (Fig. 5), moths released in the canopy
than canopy-released moths (Expt. 5: p were caught significantly more often than
GROUND = 0.227 v^. p CANOPY 0.435; n = those released on the ground in weeks two,
128 moths released on ground and in can- three and four, respectively (ti = 4.19, df=
opy; z= 3.2,P< 0.001; Expt. 6: p ground = 3, P = 0.025; t2 = 15.57, df- 3, P = 0.001;
0.422 v^. p CANOPY ^ 0.601; n = 128 moths t3 - 4.81, df- 3, P= 0.017). The four-week
released on ground and in canopy, z = 2.5, grand mean recapture rates for canopy- and
P= 0.012). ground-released moths in spring were 15.7
In replicated paired canopy and ground ± 2.4 and4.9 ± 1%, respectively (Fig. 5).
J. Entomol. Soc. Brit.Columbia 103,December2006 27
16 25
Flight temperature °C
Figure 3. Mean + S.E. percentages of irradiated (250 Gy), mass-reared male codling moths
contacting a synthetic pheromone lure (red septum with 10 jug load) in 2-min flight-tunnel tests
conducted at temperatures typical ofspring (16 °C) and summer (25 °C) after being carried for
different times (0 vs. 4 h) on an all-terrain moth delivery vehicle (ATV). Two-way ANOVA
indicates a significant temperature effect (Fi,36 = 87.44, P < 0.001) but no significant effect of
time on an ATV (Fi,36 = 0.33, P = 0.57). Paired bars within a temperature grouping having an
asterisksuperscript are significantly different(t-tests,P< 0.05).
Non-Irradiated
D 50 -
rX//l Irradiated
(OD 40 -
(/)
0)
CED 30
-
20
LU
CO
+
c 10
0)
SIR Wild
Moth type
Figure 4. Mean + S.E. percentages ofirradiated (250 Gy) and non-irradiated, mass-reared (SIR
moths) and wild male codling moths recaptured in pheromone-baited (red septum with 10 jiig
load) Pherocon 1-CP wing traps afterrelease in fourapple orchards, Summerland, BC. Two-way
ANOVA indicates a significant radiation effect (F] g = 15.53, P= 0.004) but no significant moth
effect (F] 8 = 0.46, P= 0.517). Paired bars within a moth type having an asterisk superscript are
significantlydifferent (t-tests, P< 0.05).
28 J. Entomol.Soc.Brit.Columbia 103,December2006
30 - ] Canopyrelease
\//A Ground release
^ 25
20
15 I
X
10
May 12-16 May 19-23 May26-30 June2-6
Testperiod
Figure 5. Mean + S.E. percentages of irradiated (250 Gy), mass-reared male codling moths
recaptured in synthetic pheromone-baited traps (red septum with 10 fig load) afterrelease on the
ground or within the canopy of apple orchards, Summerland, BC. Paired bars within each
weekly testperiodhaving an asterisksuperscript are significantly different(t-tests,P<0.05).
DISCUSSION
Our examination of flight activity and (Fig. 1). This lack ofa significant irradia-
recapture of sterile, mass-reared moths tion effect on catches with pheromone
released by the Okanagan-Kootenay SIR traps in laboratory assays is both supported
Programme has helped identify factors that and contradicted by field studies. Bloem et
contribute to low activity of sterile moths al. (1999) made several field releases in
in spring (Judd et al. 2004). Determining late June, July and August and found that
the impact ofvarious factors in a complex mass-reared moths irradiated with 250 Gy
operational SIR Programme is challenging were recaptured in female-baited traps at
because many factors interact and vary the same rate as non-irradiated moths.
irregularly across orchards and seasons. Likewise, Judd et al. (2006a) conducted
Even in controlled studies like those con- mark-release-recapture experiments in
ducted here interpretation requires careful May and August and found that mass-
consideration. reared moths irradiated with 250 Gy were
Irradiation with 250 Gy did not appear recaptured in standard monitoring traps
to impair pheromone perception and be- loaded with 1-mg codlemone lures as often
havioural response when moths were as- as non-irradiated mass-reared moths. How-
sayed under controlled laboratory condi- ever, in the September study reported here
tions. In flight-tunnel assays, equal propor- (Fig. 4), we found that irradiation did cause
tions ofirradiated and non-irradiated mass- a reduction in recapture of both mass-
reared moths were caught in traps baited reared and wild codling moths in traps
with 10 |ig pheromone lures (Fig. 1). Al- baited with 10 |ig lures.
though catches with pheromone lures were The conclusion we draw from these
lower at 16 than at 25 °C, there was no various data sets is that small spring-time
significant difference in the proportions of catches ofsterile moths inpheromone traps
irradiated and non-irradiated moths caught is not caused by radiation-induced impair-
at each ofthese temperatures, respectively ment ofthe olfactory system. Ifit was, this