Field Attraction of Codling Moths (Lepidoptera: Tortricidae) to Apple and Pear Fruit, and Quantitation of Kairomones from Attractive Fruit

Transcription

1 BEHAVIOR Field Attraction of Codling Moths (Lepidoptera: Tortricidae) to Apple and Pear Fruit, and Quantitation of Kairomones from Attractive Fruit PETER J. LANDOLT 1 AND CHRISTELLE GUÉDOT USDAÐARS Yakima Agricultural Research Laboratory, 5230 Konnowac Pass Road, Wapato, WA Ann. Entomol. Soc. Am. 101(3): 675Ð681 (2008) ABSTRACT Male and female codling moths, Cydia pomonella (L.) (Lepidoptera: Tortricidae) responded to fruit-baited traps in orchards. Numbers of codling moths trapped with immature uninfested s (Malus spp.), immature s infested with larval codling moth, fresh ripe s, stored ripe s, or fresh ripe pears (Pyrus spp.) were signiþcantly greater than in unbaited traps. Greatest numbers of codling moths were captured in traps baited with ripe ÔBartlettÕ pears, but direct comparisons of these fruit types were not made. Females captured in traps baited with ripe s or pears were primarily mated and had developing or mature eggs, and smaller numbers of females trapped were unmated without eggs or were postreproductive. Volatile compounds sampled from infested immature ÔRed DeliciousÕ s that were attractive in traps showed emission of two known codling moth host kairomones: (E,E)- -farnesene as well as small amounts of -caryophyllene. Collections of volatile chemicals from ripe ÔBraeburnÕ s that were attractive in traps showed strong emission of the codling moth kairomones 2-methylbutyl acetate, butyl hexanoate, hexyl hexanoate, and (E,E)- -farnesene, and very small amounts of the kairomones (R)-limonene and (E)- -farnesene. Volatile collections made from ripe Bartlett pears that were attractive in traps indicated strong emission of the codling moth kairomones butyl hexanoate, ethyl (E,Z) 2,4-decadienoate and (E,E)- -farnesene, and small amounts of the kairomones 2-methylbutyl acetate, hexyl hexanoate, -caryophyllene, (E)- -farnesene, and (E,E)-farnesol. KEY WORDS codling moth,, pear, host-þnding, attraction The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), has an oligophagous host range that includes (Malus spp.), pear (Pyrus spp.), crab (Malus spp.), and quince (Cydonia spp.) in the Rosaceae and walnut (Juglans spp.) in the Juglandaceae. In Washington state, there are ordinarily two generations per year, with adult ßight primarily occurring during May into June and again from late July into early September (Knight and Light 2005). Because s and pears ripen and are harvested from late August into October, most oviposition by female codling moths occurs when s and pears are not ripe. Codling moth host Þnding and host selection likely include orientation of adults and larvae to host kairomones. Female codling moths are attracted, in olfactometer and ßight tunnel assays, to host fruit and host fruit with foliage (Wearing et al. 1973; Yan et al. 1999; Reed and Landolt 2002; Hern and Dorn 2002, 2004; Coracini et al. 2004; Vallat and Dorn 2005). Neonate larvae respond positively in olfactometers to odors of fruit (Sutherland 1972; Russ 1976; Landolt et al. 1998, 2000). 1 Corresponding author, landolt@yarl.ars.usda.gov. Studies to determine the roles of particular volatile host chemicals in host Þnding of codling moth adults have yielded numerous antennal-active compounds, as well as a number of attractants and coattractants. Attractants reported are butyl hexanoate, -caryophyllene, ethyl (E,Z)-2,4-decadienoate (pear ester), (E,E)- -farnesene, (E)- -farnesene, (E,E)-farnesol, hexyl hexanoate, R-( )-limonene, and 2-methylbutyl acetate (Sutherland et al. 1974; Light et al. 2001; Hern and Dorn 1999, 2001, 2004; Ansebo et al. 2004; Coracini et al. 2004; Vallat and Dorn 2005). Questions remain regarding codling moth chemolocation of host fruit and the roles of kairomones in codling moth host Þnding. Observed responses to the kairomones listed above do not adequately explain how codling moths may Þnd host fruit by chemoorientation behavior. Our understanding of codling moth host Þnding has not provided useful tools for codling moth management, with the exception of ethyl-(e,z)-2,4-decadienoate. Most of these kairomones, although identiþed as attractants, have not been demonstrated to be attractive or coattractive in the Þeld, and their role in codling moth host Þnding behavior is therefore unclear. The two host chemicals that are demonstrated to be attractive in the Þeld [ethyl (E,Z)- 2,4-decadienoate and -farnesene] seem to vary in

2 676 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 101, no. 3 their performance among geographic areas and hosts, and they are differentially attractive to male and female moths (Coracini et al. 2004, Kutinkova et al. 2005, Trimble and El-Sayed 2005). Ethyl (E,Z)-2,4-decadienoate is produced by pear fruit primarily when ripe, after most oviposition by codling moth is over, leaving open the question of how codling moths might use this host kairomone to locate host fruit for oviposition. -Farnesene is produced principally by foliage of rather than fruit (Bengtsson et al. 2001). We do not know whether the observed attractiveness of these synthetic kairomones fully accounts for kairomonally mediated behavior as seen in the laboratory and expected in the Þeld. We report here evidence of codling moth orientation to host fruit in the Þeld, with assessments of the attractiveness of immature, infested, and ripe s, as well as ripe pears. We determined the reproductive status of female moths captured in traps, and quanti- Þed the amounts of known codling moth host kairomones that were emitted by immature infested ÔRed DeliciousÕ s, ripe ÔBraeburnÕ s, and ripe ÔBartlettÕ pears. We sought to demonstrate Þeld responses by both sexes to fruit, to determine whether female codling moths are attracted to fruit when mated and fecund (when capable of ovipositing), and to assess the presence of known kairomones in relation to any observed moth attraction to fruit. Such Þndings might guide subsequent work to clarify the roles of host plant chemicals in host location behavior and possibly to discover new kairomones for use in monitoring and managing the codling moth in orchards. Materials and Methods For all trapping experiments, the Universal moth trap (Agrisense Inc., Pontypridd, South Wales, United Kingdom) was used. Fruit used as bait were placed within the bucket of the trap, along with a 6.4-cm 2 piece of Vaportape (Hercon Environmental Inc., Emigsville, PA) to kill captured moths. Traps were placed in commercial orchard trees in Yakima County, WA, at a height of 3 m, with 10 m between adjacent traps. Traps were checked weekly, at which time all moths were removed, fruit were replaced, and treatments were randomized within each block. Experiment 1. Response to Uninfested Apples and Infested Immature Apples. This experiment evaluated infested immature s and uninfested immature s as bait in traps. All fruit were 2.5Ð3 cm in diameter green Red Delicious s picked in a local commercial orchard. Treatments were unbaited traps as a control, traps with four immature s, and traps with four infested immature s. Fruit were infested in the laboratory by holding each in a 0.5-liter plastic cup with a third instar from the laboratory colony. Fruit were then held in the laboratory for 2 d before placement in traps in the Þeld, and infestation was conþrmed by the presence of an entrance wound and frass from the larva. Ten replicate blocks were set up in a Red Delicious orchard on 17 July 2003, and they were maintained for 3 wk. Experiment 2. Response to Infested Immature Apples and Ripe Apples. This experiment evaluated ripe s and immature s infested with codling moth larvae. Immature Red Delicious s were picked in a commercial orchard. These fruit were 5Ð6 cm in diameter and green, and they were infested as described above with codling moth larvae in the laboratory. These fruit were used in traps 2 d after being successfully infested. Ripe Braeburn s from the 2003 New Zealand crop were purchased from a local grocery store, and they were 8 cm in diameter. Because of the difference in sizes of the fruit, four infested immature s or one ripe were used per trap. A randomized complete block experimental design was used, with 10 replicate blocks, each consisting of an unbaited control trap, a trap baited with four infested immature s, and a trap baited with one ripe. Traps were set up in a ÔGranny SmithÕ orchard on 8 August 2003, and they were maintained for 2 wk. Experiment 3. Response to Ripe Apples. This test evaluated moth responses to ripe s. Apples were 8-cm-diameter Braeburn fruit from the 2006 New Zealand crop. Ten traps, each baited with one, were paired with unbaited traps in Granny Smith, ÔGolden DeliciousÕ, and Red Delicious orchards. Traps were placed in the upper canopy of trees, 10 m apart. The 20 traps were placed in the Þeld on 19 May 2006, and they were maintained for 3 wk. Experiment 4. Response to Controlled Atmosphere (CA)-Stored Ripe Apples. This test evaluated ripe s that had been stored for much of the year in a commercial warehouse under CA storage conditions. Fruit were Braeburn s, from the 2006 Washington crop, and they were 8 cm in diameter. Twenty traps, each baited with one, were paired with an unbaited trap. These were monitored through June and July Traps were placed in ÔGalaÕ, ÔRed ChiefÕ, and ÔRed DeliciousÕ orchards. Experiment 5. Response to Immature Apples, Infested Immature Apples, and Uninfested Ripe Apples. This test evaluated immature s, immature infested s, and ripe s. Immature s were ÔFujiÕ, 4 cm in diameter, picked from a local commercial orchard. Some of these were infested with codling moth larvae as described above. Ripe s were Braeburn, 8 cm in diameter, and they were from the 2006 New Zealand crop. Because of the size differential between immature and ripe fruit, four immature or one ripe fruit were used per trap. A randomized complete block experimental design was used, with 10 replicate blocks. Traps were placed in the upper third of the canopy, 10 m apart, in commercial orchards of Red Delicious and Granny Smith s. Traps were set up 26 July 2006, and they were maintained for 3 wk. Experiment 6. Response to Ripe Apples and Ripe Pears. This trapping experiment evaluated ripe s and ripe pears in traps. Apples were Braeburn fruit from the 2006 New Zealand crop, and one fruit was used per trap. Pears were Bartlett fruit purchased from a local wholesale distributor, and they were from the 2006 California crop. One pear was used per trap. A

3 May 2008 LANDOLT AND GUÉDOT: CODLING MOTH ORIENTATION TO HOST FRUIT IN FIELD 677 randomized complete block design was used, with each of 10 replicate blocks including an unbaited trap, a trap with a Braeburn, and a trap with a Bartlett pear. This experiment was set up on 25 July 2006 in commercial orchards of Red Delicious, Golden Delicious, and Granny Smith s, and it was maintained for 2 wk. Samples of female codling moths captured in traps baited with ripe s and ripe pears in experiments 2 and 6 were dissected to determine their mating status, presence of abdominal fat, and presence of mature-sized eggs. Mating status was determined by the absence or presence of spermatophores in the female bursa copulatrix. Moths were scored for an absence, presence, or abundance of abdominal fat. Largest eggs were measured and mature-sized eggs were counted, and any complete lack of eggs was also noted. Measurements were made under a binocular dissecting microscope equipped with an ocular micrometer. Using these criteria, females were determined to be 1) unmated and immature, with no spermatophores, usually no mature eggs, and with abundant fat in the abdomen; 2) mated and fecund, with one or more spermatophores and with eggs; and 3) postreproductive, mated but with fat and no eggs. Quantitation of Attractive Volatiles Emitted by Ripe Apple and Pear Fruit. Volatile chemicals were collected from some of the same types of fruit that were used to bait traps. Samples of volatiles were obtained in August 2006 (n 3) and in August 2007 (n 3) for ripe Bartlett pears from the 2006 and 2007 California crops, in August 2006 for Braeburn s from the 2006 New Zealand crop (n 3), and in June 2007 for infested immature Red Delicious s (n 3) fresh from the Þeld and then infested using the methods described for the previous trapping experiments. The volatile collection system was composed of a compressed air cylinder as an air source, a ßow meter, a charcoal Þlter & D Hydrocarbon Trap, R & D Separations, Rancho Cordova, CA), a glass holding jar, and a SuperQ trap (Agricultural Research Science, Inc., Gainesville, FL). Metered, Þltered air passed through the holding jar into a SuperQ trap to remove volatile compounds from the air. Air was provided at a rate of 150 ml/min, and it was passed through the charcoal Þlter before it entered the holding jar. The holding jar was a 0.5-liter glass jar in which the fruit was placed. Flow meter, charcoal Þlter, holding jar, and SuperQ trap were connected by 0.6-cm internal diameter Teßon tubing. These collections were made for 1 h, after which the trap was extracted with 250 l of methylene chloride. An internal standard (20 ng of decanyl acetate in 10 l of methylene chloride) was added to the extract before it was reduced under nitrogen to 2 l, which was then analyzed using Gas chromatography-mass spectrometry GC-MS. For each volatile collection from a fruit, a 1-h collection was Þrst made with no fruit in the volatile collection system (system blank). The SuperQ trap was removed for extraction and analysis. A fruit was then placed in the chamber, and the system was purged for 15 min without a trap on line. A clean Super Q trap was then placed on line, and a 1-h collection of fruit odorants was made. The glass holding jar and Teßon tubing downwind of the jar were then washed with hot soapy water, rinsed with acetone, rinsed with hexane, and then baked in an oven at 300 C for4h. This procedure was conducted for each of three ripe Braeburn s, each of six ripe Bartlett pears, and for three batches of 10 infested immature Red Delicious s. GC-MS analyses were done on an Agilent 6890 Plus gas chromatograph (Agilent Technologies, Palo Alto, CA) with a model 5973 electron impact mass selective detector (quadripole mass spectrometer for a detector). The gas chromatograph was equipped with a DB-1 capillary column, 60 m 0.25 mm i.d., with a m Þlm thickness (J & W ScientiÞc, Folsum, CA). Helium linear velocity was 60 cm/s, with a temperature program starting at 40 C for 2 min, increasing by 10 C/min up to 200 C, maintained for 40 min. Using this program, retention times were determined for (E,E)- -farnesene, (E)- -farnesene, (E,E)-farnesol, ethyl (E,Z)-2,4-decadienoate, hexyl hexanoate, 2-methylbutyl acetate, butyl hexanoate, -caryophyllene, and (R)-limonene. Butyl hexanoate, hexyl hexanoate, 2-methylbutyl acetate, (E,E)-farnesol, -caryophyllene, (R)-limonene and ethyl (E,Z)-2,4- decadienoate were purchased from Aldrich (Milwaukee, WI), and -farnesene from Bedoukian Research Inc. (Danbury, CT). (E,E)- -farnesene was obtained from stored ripe Red Delicious s, using the procedures of Landolt et al. (2000). For each analysis of a fruit volatile collection sample, a sequence of GC runs was made. First, a methylene chloride solvent sample was run as a blank followed by a 1- l aliquot of a solution of 20 g/ml ethyl-(e,z)-2,4-decadienoate, a 1-h system blank from the volatile collection system, and then the 1-h collection from the fruit. The estimated limit of detection in these analyses was 0.1-ng/h collection. IdentiÞcations of peaks of interest in volatile collections were made Þrst by comparing mass spectra of unknowns to the NIST98 library of compounds (National Institute of Standards and Technology, Gaithersburg, MD). ConÞrmation of the structural assignment was then made by comparing the GC retention time of the peak of interest in the volatile collection with the retention times of an authentic standard. Paired treatments in trapping experiments were compared using the WilcoxonÕs signed rank test. Multiple treatment trapping tests were evaluated using TukeyÕs test, following an analysis of variance (ANOVA). Statistical analyses were done using StatMost software (DataMost 1995). Results Experiment 1. Response to Uninfested Apples and Infested Apples. Numbers of male and female codling moths in traps baited with either uninfested immature Red Delicious s or infested immature Red Delicious s were signiþcantly greater than numbers in unbaited control traps (ANOVA: F 2.65, df 89,

4 678 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 101, no. 3 Table 1. Mean numbers of male and female codling moths captured per week in traps baited with fruit in commercial orchards (Yakima County, WA) Control Immature Infested immature Ripe NZ a Ripe WA a Ripe pear Exp. 1. July 2003 Females a b b NT NT NT Males a b b NT NT NT Exp. 2. Aug Females a NT b b NT NT Males a NT b b NT NT Exp. 3. MayÐJune 2006 Females a NT NT b NT NT Males a NT NT b NT NT Exp. 4. JuneÐJuly 2007 Females a NT NT NT b NT Males a NT NT NT b NT Exp. 5. Aug Females NT NT Males a a a b NT NT Exp. 6. Aug Females NT NT b NT c Males a NT NT b NT c Means within a row followed by the same letter are not signiþcantly different at P Two-treatment comparisons were by the WilcoxonÕs signed rank test, following no assumption of equal variances among treatment differences. Multiple treatment comparisons were by ANOVA followed by a TukeyÕs test. NT, not tested. a Ripe New Zealand (NZ) s are from the current years crop, whereas ripe Washington (WA) s are from the preceding yearõs harvest. P 0.05 for females; F 6.38, df 89, P for males) (Table 1). Numbers of moths in traps with infested s were not signiþcantly greater than numbers of moths in traps with uninfested s. Two hundred and thirty three female and 411 male codling moths were captured in this experiment. Experiment 2. Response to Infested Immature Apples and Ripe Apples. Numbers of male and female codling moths captured in traps baited with either infested immature Red Delicious s or ripe Braeburn s were greater than in unbaited traps (ANOVA: F 3.67, df 59, P 0.03 for females; F 5.36, df 59, P for males) (Table 1). Numbers of moths in traps baited with infested immature s were not signiþcantly different from numbers trapped with ripe s. One hundred twenty seven female and 152 male codling moths were captured in this experiment. Experiment 3. Response to Fresh Ripe Apples. Numbers of male and female codling moths in traps baited with ripe Braeburn s were signiþcantly greater than in unbaited traps (Z 3.72, df 29, P for males; Z 3.62, df 29, P for females) (Table 1). Fifty eight female and 61 male codling moths were captured in this experiment. Experiment 4. Response to CA-Stored Ripe Apples. Male and female codling moths were trapped with ripe Braeburn s that had been in storage conditions since the preceding harvest in Washington (Z 3.06, df 19, P for males; Z 2.93, df 19, P for females) (Table 1). Thirty-three female and 34 male codling moths were captured in traps baited with s in this test. Experiment 5. Response to Uninfested Immature, Infested Immature, and Ripe Apples. Numbers of male codling moths in traps baited with ripe Braeburn s were signiþcantly higher than in unbaited traps or traps baited with uninfested immature, or infested immature Fuji s (ANOVA: F 1.72, df 119, P 0.17 for females; F 3.91, df 119, P 0.01 for males) (Table 1). Sixteen female and 23 male codling moths were captured in this test. Experiment 6. Response to Ripe Apples versus Ripe Pears. Numbers of male and female codling moths in traps baited with ripe Braeburn s were signiþcantly greater than the numbers in unbaited traps (ANOVA: F 13.4, df 59, P for females; F 11.1, df 59, P for males). Numbers of codling moths captured in traps baited with ripe Bartlett pears were signiþcantly greater than numbers of codling moths in unbaited traps and in traps baited with ripe s (Table 1). One hundred eight female and 152 male codling moths were captured in this test. Female codling moths trapped with ripe s in experiments 2 and 6, or with ripe pears, were in a similar reproductive state. These included a small portion that were unmated and some that were postreproductive, but with a majority that were mated and with eggs (Fig. 1). Statistically, there was no effect of collection date (month) or fruit type on relative numbers of reproductive (category 2) versus nonreproductive (categories 1 and 3) females ( , P 0.25). Quantitation of Attractive Volatile Compounds Emitted by Fruit. Two of the nine kairomone attractants were detected in volatiles from immature infested Red Delicious s: large amounts of (E,E)- -farnesene and small amounts of -caryophyllene (Table 2). Six of the nine kairomone compounds were emitted by ripe Braeburn s (Table 2). These emissions included large amounts (100 ng/h per ) of 2-methylbutyl acetate, butyl hexanoate, hexyl hexanoate, and (E,E)- -farnesene, and very small

5 May 2008 LANDOLT AND GUÉDOT: CODLING MOTH ORIENTATION TO HOST FRUIT IN FIELD 679 Fig. 1. Percentages of female codling moths captured in traps with fruit that were unmated (category I), mated and with developing oocytes or eggs in the abdomen (category II), or mated with no fat or developing eggs in the abdomen (category III). Moths were captured in traps baited with ripe s in June (black bars) (n 13), ripe s in August (gray bars) (n 11), or ripe pears in August (white bars) (n 57). amounts ( 1 ng/h per ) of (R)-limonene and (E)- -farnesene. -Caryophyllene, ethyl (E,Z)-2,4- decadienoate, and (E,E)-farnesol were not detected in volatiles emitted by ripe Braeburn s. Seven of the nine kairomone compounds measured were emitted by ripe Bartlett pears (Table 2). These emissions included relatively large amounts of butyl hexanoate, ethyl (E,Z)-2,4-decadienoate, and (E,E)- -farnesene, and very small amounts of 2-methylbutyl acetate, hexyl hexanoate, -caryophyllene, and (E,E)-farnesol. (R)-Limonene and (E)- -farnesene were not found in the volatiles of any of the ripe Bartlett pears. Discussion This work demonstrates attraction of codling moth adults in the Þeld to s and pears. We interpret the capture of moths in traps baited with fruit as evidence Table 2. Emission of attractive codling moth host kairomones from Braeburn s and Bartlett pears Kairomone Infested immature ng/h per fruit Uninfested ripe Uninfested ripe pear (R)-Limonene Methylbutyl acetate Butyl hexanoate Hexyl hexanoate Caryophyllene Ethyl (E,Z)-2, decadienoate (E)- -Farnesene (E,E) Farnesene (E,E)-Farnesol Means of 0.0 are less than the detectable limit estimate of 0.1 ng/h per fruit. of orientation to the odor of fruit within the bucket of the trap. Prior work has demonstrated codling moth turning and moving upwind in response to host fruit and foliage in olfactometers (Yan et al. 1999, Vallat and Dorn 2005), as well as oriented upwind ßight responses to fruit in ßight tunnels (Bengtsson et al. 2001, Reed and Landolt 2002). Our study seems to provide the Þrst experimental evidence of attraction of adult codling moth to host fruit under Þeld conditions, although Bengtsson et al. (2001) provided an anecdotal account of apparent attraction to hosts by codling moth adults in an orchard. Field evidence of attraction by codling moth to host fruit gives validity to efforts to identify new host attractants and host attractant blends from volatiles, with some expectation that those lures will be useful for trapping both male and female codling moths. The demonstration of moth attraction to fruit in traps in the Þeld also provides a method for direct comparisons between host fruit and various host chemicals to determine the relative attractiveness of putative kairomones. We do not yet know whether the identiþed kairomones that are attractive in the Þeld (pear ester by Light et al. 2001; -farnesene by Coracini et al. 2004) are comparable with host fruit odor in their attractiveness to codling moths, or whether additional attractants or attractant synergists are emitted by and pear fruit. Kairomones detected in emissions from infested immature Red Delicious s were -caryophyllene and (E,E)- -farnesene. (E,E)- -Farnesene was attractive to female codling moths in an arena type assay (Sutherland et al. 1974) and in an olfactometer (Hern and Dorn 1999), but not in the Þeld (Coracini et al. 2004), whereas -caryophyllene was attractive to female codling moths in a Y-tube olfactometer (Vallat and Dorn 2005). Both compounds elicit antennal responses from codling moths (Bengtsson et al. 2001). Our analyses of volatile chemicals from ripe Braeburn s indicated strong emission of butyl hexanoate, 2-methylbutyl acetate, hexyl hexanoate, and (E,E)- -farnesene, among many other compounds. These compounds were found in volatiles from mature or ripe fruit (Sutherland et al. 1974, Mattheis et al. 1991, Bengtsson et al. 2001, Hern and Dorn 2001, Vallat and Dorn 2005). However, the presence of these different compounds varied among these published studies, possibly in relation to fruit maturity and variety. The four compounds all elicit antennal responses in codling moths (Backmann et al. 2001, Bengtsson et al. 2001, Ansebo et al. 2004), leading to the hypothesis that they are important to host Þnding. In an olfactometer type assay, hexyl hexanoate and (E,E)- -farnesene were attractive to codling moths (Hern and Dorn 1999, 2001). Butyl hexanoate was found to be attractive to female codling moth in both olfactometer and ßight tunnel assays (Hern and Dorn 2004), but there are no demonstrations of activity in the Þeld. -Farnesene attracts male codling moths in the Þeld (Coracini et al. 2004), and it was emitted by ripe Braeburn s in our analyses, only in very small amounts. In summary, known behavioral responses to

6 680 ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA Vol. 101, no. 3 these chemicals emitted by attractive fruit do not seem to explain the codling moth attraction to ripe fruit observed in this study. Our analyses of volatiles from ripe Bartlett pear fruit indicate strong emission of butyl hexanoate, ethyl (E,Z)-2,4-decadienoate,and(E,E)- -farnesene.ethyl- (E,Z)-2,4-decadienoate is reported as a volatile of ripe pear fruit (Shiota 1990), and butyl hexanoate (Mattheis et al. 1991) and (E,E)- -farnesene (Sutherland et al. 1974) are known from fruit. All three of these chemicals are active in GC-electroantennal detector using female codling moth (Bengtsson et al. 2001, Ansebo et al. 2004). Ethyl-(E,Z)-2,4-decadienoate, also known as pear ester, is a useful attractant for trapping male and female codling moths in walnut groves and and pear orchards in the United States (Light et al. 2001; Knight and Light 2001, 2005). The capture of male and female codling moths in traps with ripe pears may be explained by the emission of ethyl-(e,z)-2,4-decadienoate from those fruit. Fruit, whether immature or ripe, fresh or from longterm storage, or pear, were attractive to male as well as female codling moths, and to females with varied reproductive states. It is suggested that female attraction to odor is host-seeking behavior in relation to oviposition (Yan et al. 1999) and that male attraction to odor is in relation to mate Þnding (Coracini et al. 2004). It is puzzling why unmated female moths or female moths with no eggs are attracted to s or pears, if the female moth response to fruit odor is a strategy to locate oviposition sites. Knight and Light (2005) found that a varying proportion (20Ð60%) of females responding in the Þeld to ethyl (E,Z)-2,4-decadienoate were unmated. In this study, the three samples of females that were dissected were 5.4, 9.1, and 14% unmated. It is not known why female codling moths are attracted to ripe fruit. Attraction of codling moth to ripe fruit for the purpose of ovipositional host Þnding is not expected because nearly all oviposition by codling moth in the Þeld occurs before fruit on trees ripen. Previous studies of codling moth adult orientation to host fruit have used immature fruit (Yan et al.1999, Reed and Landolt 2002) or both immature and mature fruit (Vallat and Dorn 2005), and studies of codling moth orientation to host fruit chemicals were based on the chemistry of immature fruit (Backmann et al. 2001), mature fruit (Ansebo et al. 2004, Hern and Dorn 2004), both immature and mature fruit (Coracini et al. 2004), or ripe fruit (Light et al. 2001). The odor of fruit changes throughout the season, with different chemical constituents dominating emissions early in the season when the Þrst codling moth ßight occurs, later in the season when the second ßight occurs, and also when fruit are fully ripe and are harvested (Mattheis et al. 1991, Vallat and Dorn 2005). It is also likely that the odorant proþles of and pear fruit vary with the fruit variety, and with longterm storage under controlled atmosphere conditions. We do not yet know how or if expected variation in odor makeup of and pear varieties affects attractiveness of fruits to codling moth. An additional hypothesis to explain moth response to ripe fruit is that moths are seeking adult feeding sites, rather than, or in addition to, oviposition sites. This hypothesis is supported by other aspects of codling moth behavior. Codling moths feed on sugar and are attracted to (can be trapped with) syrups, fruit juices, and sweet baits (Yothers 1927, Eyer 1931) as well as acetic acid (Yothers 1927, Dethier 1947), which is a volatile product of sugar fermentation by bacteria and other microbes and is found in sweet baits (Utrio and Eriksson 1977). Both male and female codling moths are attracted to these baits and to acetic acid (Dethier 1947), whereas only females would be expected to seek oviposition sites (immature or unripe fruit). However, males also might seek female oviposition sites to intercept females as potential mates. We hypothesize then that ripe fruit may provide a source of sugar for codling moth adults, and some responses to host kairomones may be a strategy to locate adult food. Acknowledgments Technical assistance was provided by J. Brumley and D. Green. We thank D. Hallauer, S. Leach, S. Teslo, and L. Braun for use of orchards. Helpful suggestions to improve the manuscript were made by D. Horton, D. Robacker, and R. Zack. This work was supported in part by a grant from the Washington State Tree Fruit Research Commission. References Cited Ansebo, L., M.D.A. Coracini, M. Bengtsson, I. Liblikas, M. Ramirez, A. K. Borg-Karlson, M. Tasin, and P. Witzgall Antennal and behavioral response of codling moth Cydia pomonella to plant volatiles. J. Appl. Entomol. 128: 488Ð493. Backmann, A. C., M. Bengtsson, A. K. Borg-Karlson, O. Liblikas, and P. Witzgall Volatiles from (Malus domestica) eliciting antennal responses in female codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae): effect of plant injury and sampling technique. Z. Naturforsch. 56: 262Ð268. Bengtsson, M., A. C. Backmann, I. Liblikas, M. I. Ramirez, A. K. Borg Karlson, L. Ansebo, P. Anderson, J. Lofqvist, and P. Witzgall Plant odor analysis of : antennal response of codling moth females to volatiles during phenological development. J. Agric. Food Chem. 49: 3736Ð3741. Coracini, M., M. Bengtsson, L. 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