(Diptera: Tephritidae) in Field Trials

HORTICULTURAL ENTOMOLOGY

Attractiveness of 79 Compounds and Mixtures to Wild Ceratitis capitata (Diptera: Tephritidae) in Field Trials ˜ A-GINER,1 ASUNCIO ´ N GANDIÁ-BALAGUER, MARIA M. HERNAŃDEZ-ALAMO ´ S, VIĆTOR CASAN CARMEN MENGOD-PUERTA, ANTONIO GARRIDO-VIVAS,2 JAIME PRIMO-MILLO, AND ´ FERA3 EDUARDO PRIMO-YU Instituto de Tecnologõá Quõ´mica, Universidad Polite´ cnica de Valencia-C.S.I.C., Avda. Los Naranjos s/n, 46022, Valencia, Spain

J. Econ. Entomol. 94(4): 898Ð904 (2001)

ABSTRACT Seventy-nine volatile compounds chosen from those emitted by Mediterranean fruit ßy males, fruits and food baits, were tested for their attractiveness to females of Ceratitis capitata (Wiedemann) in Þeld trials with a wild population. To correct for density ßuctuations, the results were presented as a percentage of males caught in the same type of traps baited with trimedlure, a known male attractant. The mixtures of corn steep liquor with ammonia compounds and amines were the most effective attractants for females. Other compounds exhibiting C. capitata attraction were a mixture ethyl acetate⫹acetic acid⫹ethanol for both sexes, and p-cymene, 1,3-diethylbenzene and borneol for females. KEY WORDS Ceratitis capitata, Mediterranean fruit ßy, attractants

CERATITIS CAPITATA (WIEDEMANN) causes serious damage to crops in tropical and subtropical areas. The Þght against this pest is generally carried out by aerial bait spraying of protein hydrolysate attractants with organophosphorous insecticides. Area-wide spraying of these broad-spectrum insecticides is the cause of protests by local inhabitants and ecological groups (Batkin 1995). More environmentally safe methods based on the use of attractants and low-toxicity compounds are currently being studied, in addition to the sterile insect technique proposed by E. Knipling (1979). These include the use of bait sprays with phototoxic insecticides (Liquido et al. 1995) or autosterilization, which uses traps baited with sterilants and speciÞc attractants (Casan˜ a-Giner et al. 1998, 1999a, 1999b). The success of these new techniques relies on the discovery of adequate attractants, especially for females. The reason for this is obvious when an autosterilizing technique is used. Good attractants of C. capitata males are available, including trimedlure (TML) (Beroza et al. 1961), ceralure (CRL) (McGovern and Cunningham 1988), and trimedlure ⫹ ammonia (Liquido et al. 1993). Heath et al. (1994, 1995, 1996) have developed synthetic food-based attractants. Many volatile compounds are emitted by C. capitata, but only a few of these compounds have been tested for pheromonal attractiveness (Jang et al. 1989, reviewed by Fletcher and Kitching 1995, Cosse´ et al. 1995). Other 1 Current address: Insect Chemical Ecology Laboratory, USDAARS, 10300 Baltimore Avenue, Building 007⫺Room 303, Beltsville, MD 20705. 2 Instituto Valenciano de Investigaciones Agrarias, Ctra. MoncadaNa´quera, km 4,500, 46113, Moncada, Valencia, Spain. Deceased. 3 To whom correspondence should be addressed.

studies have found possible female attractants among plant, fruit, or protein hydrolysate volatiles. Many of these compounds produce electroantennogram responses from female antennae or attract C. capitata females in laboratory tests (Keiser et al. 1975; Light et al. 1988, 1992; Jang et al. 1989; Dickens et al. 1990; Levinson et al. 1990; Cosse´ et al. 1995; Hernańdez et al. 1996; Prokopy and Vargas 1996; Warthen et al. 1997). However, Þeld attractiveness or effectiveness has only been investigated under varied experimental conditions for a few compounds such as (E)-6-methyl nonenoate, (E)-6-nonenol and aliphatic acids (Ohinata et al. 1977), ammonia salts (Gothilf and Levin 1987, Baker et al. 1990), alkyl-pyrazines and geranyl acetate (Baker et al. 1990), protein hydrolysates (Gothilf and Levin 1987, Heath et al. 1994, Katsoyannos and Hendrichs 1995), and ammonia compounds with methylamines and putrescine (Heath et al. 1991, 1994, 1995, 1996; Epsky et al. 1995; Ros et al. 1997; Bakri et al. 1998). Many variables inßuence the number of C. capitata caught per trap and day. Unless these conditions (or at least the most signiÞcant ones) that contribute to trap capture variability are standardized, the attractiveness of compounds assayed in different experiments cannot be properly compared. In the current study, the effectiveness of a large number of C. capitata female attractant candidates (heterocyclic nitrogen compounds, proteinaceous compounds, maleodor components, fruit and plant volatiles) were studied for the Þrst time competitively under the same environmental and experimental conditions (season, crop, trap type, trap density, and emitter). Some of the compounds had been tested previously in the Þeld

0022-0493/01/0898Ð0904$02.00/0 䉷 2001 Entomological Society of America

August 2001

CASAN˜ A-GINER ET AL.: FEMALE ATTRACTANTS FOR C. capitata

under various conditions, some had only been tested in the laboratory, and some were tested in this work for the Þrst time. We have a group of heterocyclic nitrogen compounds with 11 new candidates as attractants. Some pyrazines were tested previously by Baker et al. 1990. In other groups we tested oxygenated compounds that were identiÞed in our laboratory from C. capitata male odor (unpublished data), including a mixture of ethyl acetate ⫹ acetic acid ⫹ ethanol, as well as some compounds identiÞed by Jang et al. (1989). The above mentioned mixture has shown attractant activity for several dipterous species, including Sarcophaga carnaria (L.), Calliphora erythrocephala Meigen, Phaonia trimaculata (Bouche), Coboldia fuscipes Meigen, Megaselia sp., Morellia sp. and Drosophila funebris F. (Casan˜ a-Giner et al. 1999a). They also appear frequently in ripe, over-ripe, and fermented fruits. Corn steep liquor with ammonia, methylamine, and nitrogenous compounds were tested in a third group, based on the mixture proposed by Robacker et al. (1993, 1997) and Heath et al. (1995). To develop attracticide ingestion baits a commercial acid protein hydrolysate (Buminal) was included for comparative purposes. A fourth group of 48 plant and fruit volatiles was also tested in which some of the compounds had been identiÞed in C. capitata too. Linalool and geranyl acetate previously Þeld tested by Baker et al. (1990) were included in this group. To normalize the most inßuential variable, namely the variation in total density of the wild infestations, the results of male and female catches are expressed as a percentage of the capture of males by TML-baited traps. This parameter of capture efÞcacy relative to TML was considered a reference index in this study. We considered TML as a male total-density index. Materials and Methods Chemicals. The sources of the compounds (see Tables 1Ð 4) were Daksa (Dak) (Castello´ n, Spain), Sigma-Aldrich Quimica S.A. (SA) (Madrid, Spain), Acros Chimica N. V. (Acr) (Geel, Belgium), synthesized in our laboratory (S), Ciba-Geigy (CG) (Barcelona, Spain), Extrasynthese (Ext) (Barcelona, Spain), Fluka (Flu) (Madrid, Spain), and Bayer (Bay) (Barcelona, Spain). Purity of these compounds was ⬎98%. Trimedlure was a commercial product used for monitoring purposes from Aragonesas Agro (Madrid, Spain). Its purity was 94% and its isomeric composition was 38% TML-A, 42% TML-C, and 20% TML-B1 ⫹ TMLB2. Synthesis of 1-Pyrroline. 1-Pyrroline was obtained by treating pyrrolidine with an aqueous solution of sodium peroxodisulfate and sodium hydroxide, according to Nomura et al. (1977). The synthesis yield of trimmer/monomer of 1-pyrroline was 87/13. Flies. Field trials were conducted on natural populations of wild ßies. Traps. To standardize the type of traps, only yellow delta traps (made in our laboratory) were used with a sticky board insert (12 by 20 cm). By using a single trap type, comparisons of chemical attractiveness

899

could be made without the complicating interference of different colors, sizes, or shapes of traps. Yellow delta traps were placed 10 m apart on every other tree creating a 10-m separation in a grid block. Traps were placed 1.5 m from the ground facing south. Formulations. Each attractant was placed in the middle of a sticky board, in a glass vial (2 cm diameter by 3.5 cm high). A cylindrical cotton-wick (2.5 cm long) was inserted in the glass vial. The most volatile compounds were dispensed in a solution of 50% water ⫹ 50% sorbitol (wt:wt) to delay their evaporation. In all cases, the total weight of the attractants in each trap was 2 g. Blends were made with equal weights of each compound, except for group 3 (Table 3). Stickyboard inserts and attractants were replaced twice a week at 3- and 4-d intervals and data were collected. Field Trials. Field trials were conducted in two distant grapefruit orchards located in Pobla Llarga and Borboto´ (Valencia, Spain) during June and July of 1996 and 1997. Average daily temperature ranged between 22.8 and 24.8⬚C throughout the experiments. Fruit was ripened on the trees with high infestations of C. capitata. Test compounds were divided into four groups. Each attractant (except those from group 4) was tested in both years and in both orchards. Compounds from group 4 were tested only in the summer of 1996. For each group of compounds there were four randomized complete blocks. Each block included a trap of each tested compound, a trap with trimedlure (TML) and a blank trap. Traps were checked and counted eight times during each experiment (duration of 28 d biweekly). For groups 1, 2, and 3, two experiments were performed each summer; thus, each value is the mean of 128 counts (2 orchards * 2 summers * 4 blocks) (16 replicates). For group 4, traps were collected and counted for only 1 yr and two orchards, giving 64 counts for each value (2 orchards * 4 blocks) (8 replicates). Statistical Analysis. The female and male catches were transformed into percentage of TML male catches of the same block and counting day. For the purpose of the analyses, the four blocks, in each orchard were treated as trap-bait replications. Data were normalized by means of the arcsine (sqrt [x]) transformation and analyzed by one-way analysis of variance (ANOVA) using Statgraphics (1994). Male and female catches were compared using the Student ttest (P ⬍ 0.05) and were pooled for both years and orchards due to no statistical difference in these factors.

Results Attractancy results were presented separately for each compound group tested. All results were expressed as percentages of captured males in the standard TML-baited traps. Heterocyclic Nitrogen Compounds. The most attractive compound for females (Table 1) was 1-methylpyrrolidine (1.01%). The other attractive com-

900 Table 1.

JOURNAL OF ECONOMIC ENTOMOLOGY

Vol. 94, no. 4

Relative attractiveness of group 1, heterocyclic nitrogen compounds, as a percentage of TML catches (% mean ⴞ SD) Group 1

% catches

% catches

% total catches

Ratio of catches [么/乆]

1 2,3-dimethylpyrazine⫹2,5-dimethylpyrazinea 2 ethylpyrazine (SA) 3 2,3-dimethylpyrazine (Acr) 4 2,5-dimethylpyrazine (Acr) 5 2,6-dimethylpyrazine (Acr) 6 2-methylpiperazine (Acr) 7 2-ethyl-3-methylpiperazine (Acr) 8 2-ethyl-3,5-dimethylpyrazine (Acr) 9 2,6-dimethylpiperazine (Flu) 10 2-methylpiperidine 11 pyrrolidine (Acr) 12 3-pyrroline (Flu) 13 1-methylpyrrol (Flu) 14 2-methylpyrroline (Acr) 15 2-acetylpyrrol (Acr) 16 1-pyrroline (S) 17 1-methylpyrrolidine (Acr) 18 blank df F P

0.377 ⫾ 0.099 0.323 ⫾ 0.138 0.332 ⫾ 0.189 0.215 ⫾ 0.111 0.234 ⫾ 0.119 0.312 ⫾ 0.173 0.156 ⫾ 0.104 0.078 ⫾ 0.078 0.391 ⫾ 0.103 0.969 ⫾ 0.477 0.234 ⫾ 0.119 0.078 ⫾ 0.078 0.468 ⫾ 0.254 0.234 ⫾ 0.167 0.703 ⫾ 0.257 0.411 ⫾ 0.113 0.942 ⫾ 0.268 0.106 ⫾ 0.084 17 1.93 0.1350

0.587 ⫾ 0.094 0.324 ⫾ 0.030 0.321 ⫾ 0.104 0.481 ⫾ 0.319 0.088 ⫾ 0.079 0.156 ⫾ 0.156 0.097 ⫾ 0.078 0.234 ⫾ 0.119 0.234 ⫾ 0.119 0.469 ⫾ 0.312 0.156 ⫾ 0.104 0.312 ⫾ 0.239 0.468 ⫾ 0.208 0.078 ⫾ 0.078 0.368 ⫾ 0.104 0.330 ⫾ 0.123 1.006 ⫾ 0.331 0.242 ⫾ 0.094 17 1.65 0.0490

0.964 ⫾ 0.136 0.647 ⫾ 0.145 0.653 ⫾ 0.214 0.696 ⫾ 0.359 0.322 ⫾ 0.143 0.468 ⫾ 0.229 0.254 ⫾ 0.128 0.312 ⫾ 0.143 0.625 ⫾ 0.176 1.437 ⫾ 0.567 0.391 ⫾ 0.155 0.390 ⫾ 0.250 0.937 ⫾ 0.499 0.312 ⫾ 0.183 1.071 ⫾ 0.251 0.741 ⫾ 0.141 1.948 ⫾ 0.499 0.349 ⫾ 0.087 17 2.59 0.0005

0.64 1.00 1.03 0.45** 2.67** 2.00** 1.60 0.33** 1.67 2.07** 1.50 0.25** 1.00 3.00** 1.91** 1.24 0.94 0.44**

Each mean is calculated from 128 counts (n ⫽ 16 in the ANOVA test). **, Male and female catches differ at P ⬍ 0.05 (Student t-test). 1 g of each product or mixture. a blend at a ratio 1/1 wt:wt. Products were from SA (Sigma-Aldrich); Acr (Acros); Flu (Fluka); S (Synthetized in our laboratory). Catches of the TML baited traps were 112 ⫾ 82 ßies per trap and per day.

pounds were 2,3-dimethylpyrazine ⫹ 2,5-dimethyl pyrazine (0.59%), 2,5-dimethylpyperazine (0.48%), 2-methylpyperidine (0.47%) and 1-methylpyrrol (0.47%). With respect to total captures (males ⫹ females) the most effective attractant was again 1-methylpyrrolidine (1.95%), with no signiÞcant differences between sexes. The other most attractive compounds were 2-methylpyperidine (1.44%) and 2-acetylpyrrol (1.07%), both of which captured more males than females. 3-pyrroline had the lowest male/female (M/F) capture ratio, but its attractiveness was weak. Oxygenated Compounds Identified in Fruit Fly Male Volatiles, and a Complex Pheromone Blend. The greatest attraction of females was achieved with the mixture ethyl acetate ⫹ acetic acid ⫹ ethanol (1.98%) (Table 2). These compounds tested separately Table 2.

Relative attractiveness of group 2, male volatiles, as a percentage of TML male catches (% mean ⴞ SD) Group 2

1 2 3 4 5 6 7

showed less attractiveness than their combined (results in brackets refer to the TML catches in each group): ethyl acetate (0.51%), ethanol (0.98%), acetic acid (0.74%). The StudentÕs t-test of these individual results compared with the three component mixture showed signiÞcant difference (n ⫽ 128, P ⬍ 0.001.) When compared with the two-component mixture, in the same test, also the three component mixture was signiÞcantly different (n ⫽ 128, P ⬍ 0.05). This triplet mixture was attractive to a signiÞcantly greater proportion of females than males (ratio M/F ⫽ 0.62). With respect to total captures of both sexes, the most effective mixtures were the above triplet and ethyl acetate with either ethanol (1.68%) or acetic acid (1.44%). The mixture of eight compounds identiÞed, either in previous elseÕs work or in our laboratory, as

furfuryl alcohol (Acr) ethyl acetate⫹acetic acid⫹ethanol ethyl acetate⫹ethanol acetic acid⫹ethyl acetate ethanol⫹acetic acid pheromone blenda blank df F P

% catches

% catches

% total catches


0.373 ⫾ 0.133 1.3256 ⫾ 0.428 0.806 ⫾ 0.331 0.726 ⫾ 0.193 0.526 ⫾ 0.229 0.154 ⫾ 0.047 0.098 ⫾ 0.080 6 3.10 0.0000

0.445 ⫾ 0.121 1.9823 ⫾ 0.214 0.878 ⫾ 0.079 0.713 ⫾ 0.251 0.418 ⫾ 0.160 0.166 ⫾ 0.056 0.123 ⫾ 0.054 6 17.60 0.0062

0.818 ⫾ 0.179 3.3079 ⫾ 0.930 1.684 ⫾ 0.318 1.438 ⫾ 0.335 0.944 ⫾ 0.209 0.320 ⫾ 0.098 0.221 ⫾ 0.078 6 6.65 0.0000

0.84 0.67** 0.92 1.02 1.26 0.92 0.79

Each mean is calculated from 128 counts (n ⫽ 16 in the ANOVA test). **, Male and female catches differ at P ⬍ 0.05 (Student t-test). The attractants 1, 2, 3, 4, and 5 were dissolved in water-sorbitol 50/50 (wt:v) in order to diminish the volatility (1 g of each product or blend in 1 ml of water-sorbitol). Products were from SA (Sigma-Aldrich); Acr (Acros); Flu (Fluka); S (Synthetized in our laboratory); Dac (Dacsa); Ext (Extrasynthe` se). Catches of the TML baited traps were 102 ⫾ 28 ßies per trap and per day. a Pheromone blend was based in compounds identiÞed by Baker et al. (1985), Jang et al. (1989), Flath et al. (1993) and in our laboratory. It contained geranyl acetate (Dac)⫹linalool (Flu)⫹2,3-DMP (Acr)⫹2,5-DMP (Acr)⫹delta-1-pyrroline (S)⫹ethyl acetate⫹furfuryl alcohol (Acr)⫹methylpyrrolidine (Acr); mixed in equal ratio (1 ml of total volume).

August 2001 Table 3. SD)


Relative attractiveness of group 3, proteinaceous and ammonia compounds, as a percentage of TML male catches (% mean ⴞ

Group 3 1 2 3 4 5 6 7 8

901

CSLa CSL⫹ammoniab CSL⫹methylamine 䡠 HCl (SA)c CSL⫹ammonia⫹methylamine 䡠 HCl⫹putrescine (SA)d CSL⫹ammonia⫹methylamine 䡠 HCl⫹cadaverine (SA)e CSL⫹ammonia acetate⫹methylamine 䡠 HCl⫹cadaverinef buminal (Bay)g blank df F P

% catches

% catches

Total catches


0.604 ⫾ 0.279 1.137 ⫾ 0.335 1.462 ⫾ 0.490 2.011 ⫾ 0.391 1.956 ⫾ 0.459 2.739 ⫾ 0.464 0.536 ⫾ 0.166 0.118 ⫾ 0.237 7 5.77 0.0000

1.062 ⫾ 0.333 1.732 ⫾ 0.474 1.380 ⫾ 0.411 2.765 ⫾ 0.491 2.969 ⫾ 0.923 3.829 ⫾ 0.745 0.621 ⫾ 0.168 0.203 ⫾ 0.046 7 5.80 0.0000

1.666 ⫾ 0.262 2.869 ⫾ 0.296 2.841 ⫾ 0.317 4.767 ⫾ 0.313 4.925 ⫾ 0.733 6.568 ⫾ 0.444 1.156 ⫾ 0.097 0.321 ⫾ 0.293 7 30.69 0.0000

0.57** 0.66 1.06 0.73 0.66 0.72 0.86 0.58

Each mean is calculated from 128 counts (n ⫽ 16 in the ANOVA test). **, Male and female catches differ at P ⬍ 0.05 (Student t-test). All the solutions adjusted at pH ⫽ 8.5 with borax. Autolysate was dissolved in water (1 g autolysate in 1 ml water). Products were from SA (Sigma-Aldrich); Bay (Bayer). Catches of the TML baited traps were 132 ⫾ 38 ßies per trap and per day. a 1 ml of com steep liquor (CSL) ⫹ 1 ml water. b 1 ml of CSL ⫹ 1 ml of NH3 at 30%. c 1 ml of CSL ⫹ 1 g of methylamine 䡠 HCl. d 1 ml of CSL ⫹ 1 g of ammonia (30%)⫹methylamine 䡠 HCl⫹putrescine solution at a ratio 10:10:1. e 1 ml of CSL ⫹ 1 g of ammonia (30%)⫹methylamine 䡠 HCl⫹cadaverine solution at a ratio 10:10:1. f 1 ml of CSL ⫹ 1 g of ammonia acetate⫹methylamine 䡠 HCl⫹cadaverine solution at a ratio 10:10:1. g 1 ml of buminal ⫹ 1 ml water.

volatiles emitted by males (geranyl acetate, linalool, 2,3-dimethylpirazine (DMP), 2,5-DMP, 1-pyrroline, ethyl acetate and methylpyrrolidine) showed low attractiveness. Corn Steep Liquor (CSL) with Ammonia Compounds and Amines. The most effective mixture for the attraction of both male and female C. capitata was CSL ⫹ ammonium acetate ⫹ methylamine 䡠 HCl ⫹ cadaverine (6.57%), followed by CSL ⫹ ammonia ⫹ methylamine 䡠 HCl ⫹ cadaverine (4.93%) and by CSL ⫹ ammonia ⫹ methylamine 䡠 HCl ⫹ putrescine (4.77%). Substitution of putrescine for cadaverine and of ammonia for ammonium acetate signiÞcantly increased the captures of females and males. A commercial acid protein hydrolysate attracted fewer C. capitata than CSL or any of the tested mixtures. Corn steep liquor (alkalinized with borax) was the least attractive treatment in this group. However, it was the only treatment that attracted signiÞcantly more females than males (M/F ⫽ 0.57, P ⬍ 0.05). Volatiles Emitted by Plants and Fruits. The most effective compound for attracting females was p-cymene (2.61%), followed by 1,3-diethylbenzene (1.85%), borneol (1.75%) and 5-methyl-3-heptanone (1.65). There were signiÞcant differences between female catches with p-cymene and all the other compounds and also between the most attractive nine compounds, including 1,3-diethylbenzene and 5-methyl-2-heptanone and all other compounds (P ⬍ 0.05). With respect to total C. capitata captures, the most attractive compound was again p-cymene (3.46%), followed by 1,3-diethylbenzene (2.70%), borneol (2.35%), and 5-methyl-3-heptanone (2.20%). The lowest M/F ratio was that of p-cymene (0.33%), but only four of the top 10 attractants in group 4 attracted signiÞcantly more females than males.

Discussion The most effective attractants were the mixtures of CSL with ammonia compounds and amines (Table 3) followed by a subset of the fruit volatiles (Tables 2 and 4). The order of effectiveness in compounds that captured the most females was as follows: (1) mixture CSL ⫹ ammonium acetate ⫹ methylamine 䡠 HCl ⫹ cadaverine and two related mixtures (with ammonia or putrescine substitutions), (2) p-cymene, (3) mixture ethyl acetate ⫹ acetic acid ⫹ ethanol, (4) mixtures of CSL⫹ammonia and CSL⫹methylamine chlorhydrate, (5) 1,3-diethylbenzene and (6) borneol, (7) 5-methyl-3-heptanone, (8) linalool, (9) (E)-2-hexenoic acid, and (10) geranyl butyrate. A synergistic effect was seen in the triplet mixture acetic acid⫹ethanol⫹ethyl acetate when compared with any other mixture of two of these compounds. It is remarkable that the biological signiÞcance of this mixture can be related to their existence in fruit volatiles and also in the C. capitata. The fact that other dipterans were attracted by these compounds suggested a nonspecies-speciÞc function in C. capitata. Borneol, p-cymene and 1,3-diethylbenzene had been identiÞed in orange aromas (Wolford et al. 1971, Moshonas and Shaw 1986, Hernańdez et al. 1996). 5-Methyl-3-heptanone was identiÞed by the authors in peach air-borne volatiles (unpublished data). The geranyl acetate, identiÞed in the male C. capitata volatiles (Baker et al. 1985, Jang et al. 1989) and tested in the Þeld by Baker et al. (1990) and Heath et al. (1991), was less effective in our trials. No attractant for female C. capitata was comparable to the male C. capitata captures of TML, which may be due to a higher response to odor-attraction of the males than females in C. capitata. It occurs in other tephritids where the most powerful attractants are those for males, such as rasp-

902 Table 4.


Vol. 94, no. 4

Relative attractiveness of group 4, plant and fruit volatiles, as a percentage of TML male catches (% mean ⴞ SD) Group 4

% catches

% catches

Total catches

1 ␣-phelandrene (Dak) 2 carvacrol (Dak) 3 ␣-pinene (Dak) 4 terpinolene (Flu) 5 E-2-hexenal (SA) 6 2-octanone (Acr) 7 nonanal (Acr) 8 ␤-pinene (Dak) 9 (E)-2-hexenoic acid (Acr) 10 borneol (Dak) 11 2-hexanone (SA) 12 ␣-terpineol (Flu) 13 2-nonanone (Acr) 14 mentol (Dak) 15 longifolene (Acr) 16 isoamyl acetate (SA) 17 thymol (Dak) 18 aromadendrene (Flu) 19 3-methyl-1-butanol (Flu) 20 ethyl butyrate (SA) 21 phenyl acetone (Acr) 22 benzyl alcohol (SA) 23 2-phenylethanol (Ext) 24 1,3-diethylbenzene (Flu) 25 myrtenol (Ext) 26 bornyl acetate (Dak) 27 geranyl acetate (Dak) 28 l-canone (Dak) 29 farnesol (Ext) 30 linabol (Flu) 31 limonene oxide (Dak) 32 p-cymene (Dak) 33 isothymol (Dak) 34 3-carene (Flu) 35 cis-vervenol (Flu) 36 canfene (Dak) 37 ␣-humulene (Flu) 38 ␥-terpinene (Dak) 39 l-mentone (Dak) 40 myrcene (Dak) 41 1,8-cinneol (Dak) 42 pinane (Dak) 43 dihydromyrcene (Dak) 44 geranyl butyrate (Dak) 45 5-methyl-3-heptanone (Flu) 46 acetylfurane (SA) 47 ␣-terpinene (Ext) 48 3-methyl-2-buten-1-ol (Acr) 49 butyl acetate (SA) 50 blank df F P

0.612efgh ⫾ 0.082 0.231bcd ⫾ 0.816 0.301cde ⫾ 0.058 0.157bcd ⫾ 0.050 0.203bcd ⫾ 0.816 0.111ab ⫾ 0.058 0.051a ⫾ 0.050 0.253cd ⫾ 0.096 0.521efg ⫾ 0.129 0.601efgh ⫾ 0.141 0.522efg ⫾ 0.058 0.507efg ⫾ 0.058 0.507efg ⫾ 0.129 0.301cde ⫾ 0.129 0.444fgh ⫾ 0.082 0.501efg ⫾ 0.129 0.250cde ⫾ 0.096 0.651fghi ⫾ 0.096 0.119ab ⫾ 0.058 0.301cde ⫾ 0.058 0.302cde ⫾ 0.058 0.351cd ⫾ 0.126 0.254cde ⫾ 0.096 0.853k ⫾ 0.126 0.251de ⫾ 0.050 0.452ef ⫾ 0.050 0.550efg ⫾ 0.126 0.103abc ⫾ 0.058 0.504efg ⫾ 0.058 0.664hik ⫾ 0.171 0.603ghi ⫾ 0.082 0.850k ⫾ 0.171 0.149bcd ⫾ 0.050 0.558efg ⫾ 0.222 0.457efg ⫾ 0.171 0.101abc ⫾ 0.058 0.155bcd ⫾ 0.096 0.543efg ⫾ 0.096 0.152bcd ⫾ 0.096 0.311cde ⫾ 0.129 0.259de ⫾ 0.050 0.154bcd ⫾ 0.096 0.553efgh ⫾ 0.096 0.405def ⫾ 0.221 0.550fgh ⫾ 0.150 0.132abcd ⫾ 0.058 0.255bcd ⫾ 0.222 0.512ef ⫾ 0.081 0.321cd ⫾ 0.058 0.132abcd ⫾ 0.058 49 1.07 0.0000

0.351abc ⫾ 0.096 0.099a ⫾ 0.058 0.351abc ⫾ 0.050 0.152ab ⫾ 0.050 0.632bcd ⫾ 0.082 0.411abc ⫾ 0.082 0.051a ⫾ 0.050 0.902cde ⫾ 0.208 1.402fg ⫾ 0.245 1.751gf ⫾ 1.171 0.451bc ⫾ 0.050 0.708bcde ⫾ 0.129 1.350fg ⫾ 0.126 0.252ab ⫾ 0.050 0.314fg ⫾ 0.129 0.251abc ⫾ 0.096 0.850cde ⫾ 0.096 0.149a ⫾ 0.096 0.604bcd ⫾ 0.142 0.112a ⫾ 0.058 0.304abc ⫾ 0.577 0.250abc ⫾ 0.096 0.100a ⫾ 0.058 1.850g ⫾ 0.263 0.933de ⫾ 0.129 0.351abc ⫾ 0.096 0.954de ⫾ 0.050 0.906de ⫾ 0.129 0.551bc ⫾ 0.050 1.450fg ⫾ 0.126 0.801cde ⫾ 0.050 2.609h ⫾ 0.126 0.312abc ⫾ 0.082 0.211ab ⫾ 0.294 0.754cde ⫾ 0.058 0.200ab ⫾ 0.082 0.451bc ⫾ 0.096 0.403abc ⫾ 0.183 0.346abc ⫾ 0.058 0.951de ⫾ 0.321 0.251abc ⫾ 0.096 0.153ab ⫾ 0.050 0.999def ⫾ 0.271 1.400fg ⫾ 0.294 1.650fg ⫾ 0.222 0.171ab ⫾ 0.100 0.555cde ⫾ 0.102 0.304abc ⫾ 0.120 0.600cde ⫾ 0.230 0.171ab ⫾ 0.100 49 5.66 0.3541

0.963bcde ⫾ 0.150 0.330a ⫾ 0.100 0.652abcd ⫾ 0.073 0.309a ⫾ 0.065 0.835bcde ⫾ 0.185 0.522abcd ⫾ 0.146 0.102a ⫾ 0.065 1.155cde ⫾ 0.272 1.923ef ⫾ 0.426 2.352f ⫾ 0.481 0.973cdef ⫾ 0.073 1.215cdef ⫾ 0.151 1.857ef ⫾ 0.362 0.553abcd ⫾ 0.130 0.758f ⫾ 0.439 0.752abcd ⫾ 0.176 1.100cdef ⫾ 0.259 0.800bcde ⫾ 0.227 0.723abcd ⫾ 0.236 0.413abc ⫾ 0.107 0.606abcd ⫾ 0.756 0.601abcd ⫾ 0.151 0.354ab ⫾ 0.118 2.703fg ⫾ 0.464 1.184cdef ⫾ 0.213 0.803bcde ⫾ 0.107 1.504def ⫾ 0.196 1.009cdef ⫾ 0.330 1.055cdef ⫾ 0.073 2.114ef ⫾ 0.361 1.404def ⫾ 0.131 3.459g ⫾ 0.733 0.461abcd ⫾ 0.091 0.769abcd ⫾ 0.256 1.211bcdef ⫾ 0.338 0.301ab ⫾ 0.100 0.606abcd ⫾ 0.169 0.946cdef ⫾ 0.199 0.498abcd ⫾ 0.118 1.262cdef ⫾ 0.287 0.510abcd ⫾ 0.100 0.307ab ⫾ 0.100 1.552def ⫾ 0.316 1.805def ⫾ 0.472 2.200f ⫾ 0.484 0.303a ⫾ 0.107 0.810cd ⫾ 0.113 0.800cde ⫾ 0.133 0.900cdef ⫾ 0.300 0.303a ⫾ 0.099 49 5.99 0.0000

Ratio of catches [么/乆] 1.74 2.33 0.86 1.03 0.32** 0.27** 1.00 0.28** 0.37** 0.34** 1.16 0.72 0.38** 1.19 1.41** 2.00** 0.29** 4.37** 0.20** 2.69** 0.99 1.40 2.54** 0.46 0.27** 1.29 0.58 0.11 0.91 0.46 0.75 0.33** 0.48 2.64** 0.61 0.51 0.34** 1.35 0.44** 0.33 1.03 1.01 0.55 0.29 0.33 0.77 0.46 1.67 0.50 0.77

Each mean is calculated from 64 counts (n ⫽ 8 in the ANOVA test). Mean separation test on square root [x ⫹ 0.5] transformed data, P ⫽ 0.05). **, Male and female catches differ at P ⬍ 0.05 (Student t-test). 1 g of each product. Products were from SA (Sigma-Aldrich); Acr (Acros); Flu (Fluka); Dak (Daksa); Ext (Extrasynthe` se) Catches of the TML baited traps were 159 ⫾ 58 ßies per trap and per day.

berry ketone for the melon ßy, Dacus cucurbitae (Coquillet), (Beroza et al. 1960). From our results we conclude that the nitrogenated compounds ammonia (or those that release ammonia), amines, and protein hydrolisates can be considered the most effective attractants for female C. capitata described to the date. Additional compounds can be considered for further studies to synergize mixtures. Compounds that show activity at short range, such as those male volatiles tested by Jang et al. (1989),

have failed to attract females in our long range tests, suggesting that their mode of action may be different from the para-pheromones for male C. capitata. More research must be undertaken to improve the attractiveness of the female attractants in the Þeld. Such research should not only be based on chemical attractiveness, but also on optimal concentrations, synergistic mixtures, more adequate traps and emitters for each compound and mixture, and optimal emission. In addition, the recent development of a painted

August 2001


cylindrical dry trap with a three-component attractant (Heath et al. 1995, 1996, 1997) has demonstrated that research on the management of the chemical and visual cue interactions is crucial for advances in the detection and control of C. capitata. We propose that future testing on C. capitata attractants, the attractiveness, besides being measured as catches per trap or per day, should be referred to as the percentage of females caught with respect to trimedlure under the same conditions. Although this would not represent an absolute measurement of attractiveness, at least it could allow comparing tests done in different situations. In many biological tests there are standards to measure against (e.g., benomile to compare fungicidal activity, whatever the experimental conditions are). A trimedlure index could serve as a good standard for measuring female and male attractiveness, considering that the female/male ratio is 1. This is the natural ratio for C. capitata, and it is unlikely that in large areas the population is skewed toward any sex, and no study has shown that this occurs. In fact, the female C. capitata are those that produce fruit damage, but worldwide, including at the USDA, the trimedlure male catches are used as the main monitoring technique to initiate insecticide sprays, apart from female lures. Moreover, in our study we have demonstrated that the female C. capitata lures that are currently used are far below the detection limit of trimedlure when the experimental conditions are the same. Acknowledgments We thank our co-author Antonio Garrido-Vivas (recently deceased) for all of the support he provided in this work and for his outstanding contributions to Entomology, worldwide and especially in Spain. We thank Angel Cantin for the syntheses of some of the tested compounds. We also thank Carolyn Smith (Insect Chemical Ecology Laboratory, Beltsville, MD) for her comments and editing of the manuscript and to Bryan T. Vinyard of the Biometrical Consulting Service of the USDA (Beltsville, MD) for his statistical advice. This research is also supported by grant PN96Ð24349349 of Ministerio de Educacio´ n y Ciencia de Espan˜ a (proyecto AGF95Ð 0645).

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