Abstract. The Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), is a quarantine pest of Citrus spp. and a production pest of guava and oth
Aimé Vázquez, Kevin R Cloonan, Barukh B Rohde, Micah A Gill, Lisa K Mosser, Jonathan H Crane, Daniel Carrillo, Paul E Kendra, Attraction and Longevity of 2- and 3-Component Food Cone Lures for the Caribbean Fruit Fly,
Anastrepha suspensa(Diptera: Tephritidae),Journal of Economic Entomology, 2022;, toac102, https://doi.org/10.1093/jee/toac102The Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), is a quarantine pest of Citrus spp. and a production pest of guava and other specialty fruits in Florida. Effective monitoring lures and traps are needed for early pest detection and timely initiation of control measures. As part of a continued effort to identify attractive synthetic lures for the Caribbean fruit fly, we conducted field tests in Homestead, Florida to compare the efficacy and longevity of commercial 2- and 3-component cone lures (2C [ammonium acetate and putrescine], 3C [ammonium acetate, putrescine, and trimethylamine]), the current standards used by regulatory agencies, versus the traditional liquid protein bait consisting of hydrolyzed torula yeast and borax as a positive control. Additional lures were also field-aged and periodically brought into the laboratory to quantify residual chemical contents. Traps baited with the torula yeast-borax mixture captured the highest mean number of A. suspensa, and traps baited with the commercial 2C lures captured more flies than the 3C lures. Traps baited with torula yeast-borax also captured the highest number of nontarget Diptera. Captures with all three treatments were significantly biased toward females. Attractiveness of the 2C lure began to drop after 6–8 wk, and the 3C lure after 5–6 wk. Overall, these data suggest that the 2C cone lure is more attractive to A. suspensa than the 3C cone lure under field conditions in south Florida, and that the 2C lures are attractive for up to 8 wk.
The Caribbean fruit fly, Anastrepha suspensa (Loew), is a polyphagous fruit pest native to the West Indies that was initially detected in Florida in 1931 and then again in 1959 (Swanson and Baranowski 1972). In 1965 a third infestation was detected in Miami Springs and subsequently spread to over 23 counties in less than a year (Weems 1966). The host range of A. suspensa comprises 84 different fruit species, including guava, Psidium guajava L. (Myrtales: Myrtaceae), and Citrus spp. grown commercially in Florida (Swanson and Baranowski 1972). The Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), has also been intercepted in Florida (Thomas 2004), and an increasing volume of foreign produce flowing through Florida’s ports creates further concern that more Anastrepha spp. may enter the state (Kendra et al. 2007). The primary economic impact of A. suspensa in Florida citrus is not from direct damage to fruit but instead from the quarantine restrictions imposed on ‘fruit fly free’ zones in citrus production areas (Greany and Riherd 1993, Simpson 1993). Within these fly free zones capture of a single female fly may trigger a treatment program creating an emphasis on selective and effective monitoring tools (Epsky et al. 1993, 1994). In addition, guava is a host of many Anastrepha spp., and fruit flies cause direct damage to the fresh fruit making it unmarketable. Florida now has well over 720 acres of commercial guava, both white and pink pulped cultivars (Crane 2018). Improved monitoring and trapping may, in the future, reduce fruit losses due to fruit flies. Improved lures used to monitor and suppress tephritid populations, especially A. suspensa, could also permit the expansion of citrus growing regions in Florida (Epsky et al. 1994). Although it is presently unknown how trap captures correspond with the actual A. suspensa population levels in a given area, simulation models are being used to investigate how trap captures can predict populations of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) (Caton et al. 2022).
The first commercialized protein-based lure, Nu-Lure (Miller Chemical and Fertilizer, LLC, Hanover, PA), was developed for attracting the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), and the Mediterranean fruit fly, Ceratitis capitata (Steiner 1952). A mixture of hydrolyzed torula yeast (TY) and borax was also developed for trapping both C. capitata and Anastrepha spp. (Lopez et al. 1971, Burditt 1982) using McPhail traps (Newell 1936). Heath et al. (1994) found that both C. capitata and A. ludens were more attracted to Nu-Lure at a pH of ~8.5 compared to Nu-Lure formulations with a lower pH. Subsequent studies indicated that an increase in alkalinity results in increased ammonia release from the bait solution (Heath et al. 2009). However, in mark-release recapture studies, Calkins et al. (1984) found that the trapping efficiency, or the ability of a trap to capture a target species in a given area, was very low. To capture 90% of the flies in an area TY-baited traps would need to be deployed at a rate of at least 33 traps per 0.4 ha (Calkins et al. 1984). In addition to proteinaceous baits, bacteria isolated from the alimentary canal of field collected A. ludens, identified as Staphylococcus aureus (Rosenbach) (Bacillales: Staphylococcaceae) (strain RGM-1), were attractive to A. ludens (Rubio and McFadden 1966, Robacker 1991, Robacker et al. 1993). Although attractive, proteinaceous baits are difficult to handle in the field (Heath et al. 1995), and their attractiveness to adult flies changes over time as the bait ages (Malo 1992; Epsky et al. 1993, 2006; Torres-Quezada et al. 2021), with TY baits only being attractive to Anastrepha species for between 1-2 weeks (Calkins et al. 1984). Over the past several decades compounds have been isolated and identified from attractive materials (Epsky et al. 2014) with the ultimate goal of producing one specific suite of compounds, at a specific ratio, that could be deployed by a regional crop protection program for the detection of several different tephritid pest species (Thomas et al. 2008, Biasazin et al. 2018).
In an effort to develop a synthetic lure more attractive and easier to handle than liquid protein baits, a combination of ammonium bicarbonate (AB), pyrrolidine, and putrescine (Pt), isolated and identified from the headspace of Nu-Lure, was found to be attractive to melon flies, Zeugodacus curcurbitae (Coquillett) (Diptera: Tephritidae) (Wakabayashi and Cunningham 1991). Further analysis of Nu-Lure headspace identified a third attractive component, methylamine, and showed that a combination of AB, methylamine, and Pt, at a ratio of 10:10:1, respectively, was the most attractive blend to adult A. ludens, which the authors called ‘AMPu’ (Robacker and Warfield 1993). Additional volatile collections from the S. aureus RGM-1 strain (Robacker et al. 1993) identified trimethylamine (TMA) and acetic acid as new attractants for A. ludens (Robacker and Flath 1995). This work led to the development of a 3-component blend consisting of ammonium acetate (AA), Pt, and TMA that was attractive to both C. capitata and A. ludens (Heath et al. 1995, 1997). These compounds were subsequently incorporated into several commercial lures and over the following decade were tested for Anastrepha spp. attraction in both the laboratory and field with varying results (Robacker 1998, 1999; Thomas et al. 2001; Jang et al. 2007; Kendra et al. 2008; Thomas et al. 2008; Kendra et al. 2009; Epsky et al. 2011). For example, in Florida A. suspensa were more attracted to AA and Pt (formulated as a synthetic blend) compared to TY (Thomas et al. 2001, Hall et al. 2005, Epsky et al. 2006, Holler et al. 2006), whereas in Puerto Rico A. suspensa were more attracted to TY compared to a blend of AA and Pt (formulated as the 2C BioLure [Suterra, Bend, OR]) (Pingel et al. 2006). In comparing 2- and 3-component blends, A. suspensa were more attracted to 2-component blends of AA and Pt compared to the 3-component blend of AA, Pt, and TMA (both formulated as synthetic blends) (Holler et al. 2006) and as formulated commercial 2C and 3C BioLures (Epsky et al. 2011).
With the original 2C and 3C BioLures, each component was formulated separately as a liquid attractant loaded into a controlled-release membrane-based dispenser. Dispensers were attached to the inside lid of a trap, could potentially fall into the retention fluid, and were prone to leakage (Jang et al. 2007, Shelly et al. 2020). The separation of components in individual dispensers also presented a potential risk of losing or duplicating dispensers when deploying them in the field (Jang et al. 2007). This latter issue was addressed with the production of both the 3C BioLure Unipak (AA, Pt, TMA packaged in a single membrane-based dispenser) (Holler et al. 2009) and an alternative dispenser technology consisting of solid matrix 2C (AA, Pt) and 3C (AA, Pt, TMA) conical-shaped lures (Scentry Biologicals, Billings, MT) (Jang et al. 2007). Since the Multilure trap (a plastic McPhail-type trap; Better World Manufacturing, Fresno, CA) is regarded as the most effective trap design for capturing C. capitata and Anastrepha spp. (Davis et al. 1984, Thomas et al. 2001, Robacker and Czokajlo 2005), State and Federal survey programs use it exclusively for the detection and delimitation of these flies in Florida (USDA-APHIS-PPQ-FDACS 2001). The 2C and 3C cone lures are used in these traps because of their compact solid formulation (no leakage), ease of deployment (placement of cone into a basket on top of the trap), and the space constraints for housing lure dispensers in the Multilure trap.
Regulatory agencies in Florida are currently using the 3C cone lure in Multilure traps for detection/monitoring of both Ceratitis and Anastrepha species across the state, and in the event of an Anastrepha spp. emergency program, APHIS may use the 2C cone lure (Abbie Fox, director of the Fruit Fly Exclusion and Detection (FFED) Project at the USDA-APHIS, personal correspondence). However, the differential attraction of feral A. suspensa to 2C and 3C cone lures has not been compared in Florida. Nor has the field life or residual component analysis been investigated for either of these lures when exposed to South Florida field conditions. The current study was therefore conducted at the request of APHIS to compare the attraction and longevity of the 2C and 3C cone lures for A. suspensa during the peak fruiting season of three preferred hosts in southern Florida. We conducted replicate 10-wk field tests in guava, loquat [Eriobotrya japonica Thunb. (Rosales: Rosaceae)], and Surinam cherry [Eugenia uniflora L. (Myrtales: Myrtaceae)] to compare the efficacy and longevity of the 2C and 3C cone lures, along with the standard TY bait as a positive control, for the capture of A. suspensa. Additionally, a set of 2C and 3C cone lures were field-aged for 8 wk and periodically analyzed by ion chromatography to quantify the residual content of their individual components.
The four treatments tested in this study were:
TY-borax (three pellets in 300 ml water) (ISCA Technologies, Riverside, CA)
2C cone lure (AA + Pt; Scentry Biologicals)
3C cone lure (AA + Pt + TMA; Scentry Biologicals)
A nonbaited control trap containing only the retention fluid.
The nonbaited control, 2C cone lure, and 3C cone lure traps contained 300 ml of a 10% propylene glycol (LowTox Antifreeze + Coolant, Prestone, Lake Forest, IL) solution as a retention fluid. Multilure traps with yellow bottoms (Better World Manufacturing) were used for all treatments. The 2C and 3C cone lures were not changed for the course of this trial to monitor how A. suspensa attraction changed over time. The TY-borax treatment served as a positive control, and a fresh solution was prepared each week since this liquid bait has been reported to have an attractive field life of only 1–2 wk (Shelly et al. 2020).
Tests were conducted in guava (25°30ʹ43.0″N, 80°29ʹ54.5″W), loquat (25°30ʹ26.4″N, 80°30ʹ00.9″W), and Surinam cherry (25°30ʹ28.7″N, 80°30ʹ00.9″W) orchards located at the University of Florida Tropical Research and Education Center (UF-TREC) in Homestead, FL. Trees were in fruit during the time of these tests. Individual blocks consisted of either a single large tree, with all treatment traps placed around the periphery (Surinam cherry), or a row of trees with one trap placed per tree (guava and loquat). All traps were placed 1.5 m above ground level and were spaced at least 5 m from any other traps. Traps in guava (5 replicated blocks) and loquat (5 replicated blocks) were deployed from 5 March to 14 May 2020 (10-wk trapping period). Traps in Surinam cherry (3 replicated blocks) were deployed from 12 March to 21 May 2020 (10-wk trapping period). For Surinam cherry there were only three large trees available for this study, thus only three complete replicates were feasible. Traps were sampled weekly and insects were removed by sieving and placed into 70% ethanol for later identification in the laboratory. With TY, freshly prepared solution was placed into the reservoir; with all other treatments, the retention fluid was reused and topped off to 300 ml if necessary. After each sampling, traps were rotated within each block to reduce potential positional effects on capture. Numbers of female and male A. suspensa were recorded. Bycatches were also recorded and were placed into three separate groups: African fig fly, Zaprionus indianus Gupta. (Diptera: Drosophilidae), other Drosophila (non-Z. indianus), and all other Diptera.
Forty 2C and 3C cone lures were placed in Multilure traps and deployed in an avocado orchard at the United States Department of Agriculture, Agricultural Research Service, Subtropical Horticulture Research Station (USDA-ARS-SHRS) in Miami, FL. The purpose of this trial was to expose lures to ambient field conditions before chemical analysis of residuals; therefore, PPG was omitted from these traps to prevent insect captures and potential introduction of volatiles resulting from protein degradation. A subset of lures (n = 5) was brought into the laboratory for extraction of residual contents at 0 (1 hr), 1, 3, 7, 14, 28, 42, and 56 d. Lures were weighed and placed into individual glass jars containing 10% methanol (Thermo Fisher Scientific, Inc., Waltham, MA) in 18.2 MΩ ultrapure water (PureLab Option-Q, ELGA LabWater, UK). For the 2C cone lures, 100 ml of 10% methanol was used for extraction, and jars were placed on an orbital shaker overnight at low setting. For the 3C cone lures, 200 ml of 10% methanol was used for extraction, and jars were shaken for 2 hr at low setting.
Chemical analysis was performed in a Thermo Dionex ICS-2100 ion chromatography system (Thermo Fisher Scientific, Inc., Waltham, MA) equipped with an AS 40 autosampler, methanesulfonic acid eluent generator cartridge (MSA EGCIII), 250 × 4 mm CS12A analytical column, 50 × 4 mm GS12A guard column, CSRS 4 mm suppressor and electrical conductivity detector (ECD). Analytical grade ammonium acetate (AA) 98%, trimethylamine hydrochloride (TMA.HCl) 99%, and putrescine dihydrochloride (PUT.2HCl) 99% (Millipore Sigma, St. Louis, MO) were used for calibration. A combined calibration curve was generated for all analytes on each sampling date. Four concentration levels of a 3-component standard mix were prepared in 18.2 MΩ ultrapure water. Target concentrations for each analyte were 3.50, 17.50, 35.0, and 52.5 mg/liter for AA; 0.50, 2.50, 5.00, and 7.50 mg/liter for TMA.HCl; and 0.375, 1.875, 3.750, and 5.625 mg/liter for PUT.2HCl. System suitability was evaluated daily before analysis. An RSD <5% among three replicates of standard level 1 confirmed suitability.
Ten microliters of each cone extract were placed in individual Dionex vials and diluted to 5 ml with 18.2 MΩ ultrapure water. Samples and standards were then placed in the autosampler in the appropriate sequence. Brackets of level 3 standard were placed every 5–10 samples as check standards. A volume of 25 µl was injected into the ion chromatograph and carried through the column using 25 mM MSA at 1.0 ml/min in isocratic mode for a total of 20 min. Both the column chamber, and the conductivity cell, were kept at a constant temperature of 50oC. The suppressor was set at 74 mA. Based on the corresponding calibration curves, peak areas obtained from the chromatography analysis were converted to concentration in mg/liter by Chromeleon software (Thermo Fisher Scientific, Inc., Waltham, MA). Total residual amounts in grams were then calculated for each analyte as follows:
[Note: Residual content can be converted to the neutral or nonacidified molecule by means of their corresponding molecular weight ratios. Ammonia (17.031 g/mol) from AA (77.0825 g/mol), Pt (88.15 g/mol) from PUT.2HCl (161.07 g/mol), and TMA (59.11 g/mol) from TMA.HCl (95.57 g/mol)]. Average and standard deviation values were calculated using Microsoft Excel (Microsoft Corporation, Redmond, WA). Data were collected and summarized throughout an 8-wk timespan.
One-way analysis of variance (ANOVA) was used to test the effect of treatment on mean field captures (flies/trap/week) of A. suspensa (males and females separately) and nontarget Diptera in each of the 10-wk tests; significant ANOVAs were then followed by mean separation with Tukey HSD test. When necessary, data were square root (x + 0.5)-transformed to stabilize variance before analysis. To evaluate longevity of 2C and 3C lures, analysis by t-test was used to compare mean captures with a lure treatment vs. the nonbaited control at each weekly sampling point (Kendra et al. 2016a,b). t-Tests were also used to compare mean captures of male and female A. suspensa with each lure treatment. Regression analysis with exponential decay models was used to describe the relationship between residual content of analytes and duration of field exposure for the 2C- and 3C-cone lures. Analyses were performed using SigmaPlot 14.0 (Systat Software Inc., San Jose, CA). Unless otherwise noted, results are presented as mean ± SEM; probability was considered significant at a critical level of α = 0.05.
In the guava field test, mean captures of both female and male A. suspensa, analyzed separately, over the entire 10-wk trial were higher in traps baited with TY compared to all other treatments, and the 2C cone lure captured more females and males compared to the 3C cone lure (female: F = 50.74, df = 3,16, P < 0.001; male: F = 38.21, df = 3,16, P < 0.0001) (Fig. 1A). Examination of weekly captures (sexes combined) with TY indicates two peaks in the fly population (weeks 2 and 5) followed by a sharp decrease (Fig. 2A). Comparing mean captures from adjacent weeks, traps baited with 2C cone lures captured significantly more than nonbaited control traps up to week 6 (t = 2.47, df = 8, P = 0.039), but not week 7 (t = 1.47, df = 8, P = 0.180) (Fig. 2A). Traps baited with the 3C cone lures captured more than control traps up to week 5 (t = 3.54, df = 8, P = 0.007), but not week 6 (t = 1.79, df = 8, P = 0.112) (Fig. 2A). More ‘other Diptera (primarily unidentified muscids)’ were captured in TY-baited traps compared to all other lure types, and both 2C and 3C cone lures captured similar numbers of other Diptera (F = 40.11, df = 3,16, P < 0.001). There was no difference in capture between all lure types for the African fig fly, Z. indianus (F = 0.80, df = 3,16, P = 0.49). More other Drosophila were captured in the TY-baited traps compared to the 3C cone lure, and the 2C and 3C cone lures captured similar numbers of these other Drosophila flies (F= 42.01, df = 3,16, P < 0.001) (Fig. 3A).
In loquat, mean captures of female and male A. suspensa, analyzed separately, over the entire 10-wk trial were higher in traps baited with TY compared to all other treatments, and the 2C cone lure captured more females and males compared to the 3C cone lure (female: F = 47.87, df = 3,16, P < 0.001; male: F = 79.92, df = 3,16, P < 0.001) (Fig. 1B). The weekly captures with TY indicate a single peak in the population at week 6 (Fig. 2B), coinciding with the decline in numbers observed at the guava site (Fig. 2A). Regarding longevity, traps baited with 2C cone lures captured more than control traps up to week 8 (t = 2.71, df = 8, P = 0.026), but not week 9 (t = 1.77, df = 8, P = 0.115) (Fig. 2B). Traps baited with the 3C cone lures captured more than control traps up to week 7 (t = 2.81, df = 8, P = 0.023), but not week 8 (t = 1.93, df = 8, P = 0.089) (Fig. 2B). More other Diptera were captured in TY-baited traps compared to all other lure types, and both 2C and 3C cone lures captured similar numbers of other Diptera (F = 64.56, df = 3,16, P < 0.001). Traps baited with TY captured more African fig fly, Z. indianus than the 2C cone lure, and the 2C and 3C cone lures captured similar numbers of Z. indianus (F = 27.33, df = 3,16, P < 0.001). More other Drosophila were captured in the TY-bated traps compared to the 2C and 3C cone lures, and the 2C and 3C cone lures captured similar numbers of these other Drosophila flies (F = 65.14, df = 3,16, P < 0.001) (Fig. 3B).
In Surinam cherry, mean captures of female and male A. suspensa, analyzed separately, over the entire 10-wk trial were higher in traps baited with TY compared to all other treatments and the 2C cone lure captured more females than the 3C cone lure (female: F = 24.76, df = 3,8, P < 0.001; male: F = 12.14, df = 3,8, P = 0.002) (Fig. 1C). The weekly captures with TY indicate a single large peak in the population at week 6, similar to that observed at the loquat site (Fig. 2C). Due to the low number of replicate blocks (n = 3) at the smaller Surinam site, analysis by t-test was not appropriate for assessing lure longevity. More other Diptera were captured in TY-baited traps compared to all other lure types, and both 2C and 3C cone lures captured similar numbers of other Diptera (F = 54.19, df = 3,8, P < 0.001). There was no difference in capture between all lure types for the African fig fly, Z. indianus (F = 2.08, df = 3,8, P = 0.12). More other Drosophila were captured in the TY-baited traps compared to the 2C and 3C cone lures, and the 2C and 3C cone lures captured similar numbers of these other Drosophila flies (F = 53.36, df = 3,8, P < 0.001) (Fig. 3C).
Overall, captures of A. suspensa with TY, 2C and 3C lures were significantly biased toward females. At the guava site, mean female captures comprised 69.6 ± 0.9% with TY (t = 2.794, df = 8, P = 0.023), 72.1 ± 2.9% with 2C lures (t = 3.694, df = 8, P = 0.006), and 75.4 ± 2.4% with 3C lures (t = 5.283, df = 8, P < 0.001). At the loquat site, female captures comprised 75.9 ± 2.9% with TY (t = 3.582, df = 8, P = 0.007), 73.4 ± 2.5% with 2C lures (t = 4.798, df = 8, P = 0.001), and 74.0 ± 1.6% with 3C lures (t = 12.395, df = 8, P < 0.001). In Surinam cherry, female captures comprised 73.8 ± 2.8% with TY (t = 2.112, df = 4, P = 0.102), 78.7 ± 2.1% with 2C lures (t = 3.183, df = 4, P = 0.033), and 65.9 ± 4.2% with 3C lures (t = 1.110, df = 4, P = 0.329).
On the first day of analysis (Day 0), with only 1-hour exposure to outdoor conditions, the mean quantity of AA detected in the lure was 3.1099 ± 0.3032 g. This value is consistent with the intended total content of 3.0 g of AA as specified by the manufacturer. The mean quantity of putrescine (Pt) dihydrochloride detected initially (Day 0) was 0.1669 ± 0.0246 g, which is 15–20% lower than the intended manufacturer amount of 0.2 g (APHIS-CPHST-TIML-SOP-109 2018). A set of 5 fresh lures, extracted without outdoor exposure, contained a slightly lower amount of each chemical component (2.8209 ± 0.6293 g AA and 0.1606 ± 0.0126 g PUT.2HCl) (Table 1).
| Analyte . | Avg. amount (g) . | |
| 2C cones . | 3C cones . | |
| AA | 2.8209 ± 0.6293 | 2.8613 ± 0.2763 |
| PUT.2HCl | 0.1606 ± 0.0126 | 0.3496 ± 0.1068 |
| TMA.HCl | – | 0.5610 ± 0.1132 |
| Analyte . | Avg. amount (g) . | |
| 2C cones . | 3C cones . | |
| AA | 2.8209 ± 0.6293 | 2.8613 ± 0.2763 |
| PUT.2HCl | 0.1606 ± 0.0126 | 0.3496 ± 0.1068 |
| TMA.HCl | – | 0.5610 ± 0.1132 |
| Analyte . | Avg. amount (g) . | |
| 2C cones . | 3C cones . | |
| AA | 2.8209 ± 0.6293 | 2.8613 ± 0.2763 |
| PUT.2HCl | 0.1606 ± 0.0126 | 0.3496 ± 0.1068 |
| TMA.HCl | – | 0.5610 ± 0.1132 |
| Analyte . | Avg. amount (g) . | |
| 2C cones . | 3C cones . | |
| AA | 2.8209 ± 0.6293 | 2.8613 ± 0.2763 |
| PUT.2HCl | 0.1606 ± 0.0126 | 0.3496 ± 0.1068 |
| TMA.HCl | – | 0.5610 ± 0.1132 |
Over the 8-wk period of field aging, the residual amount of AA remaining in 2C lures declined sharply over time, and this analyte was barely detectable after 7 wk (Fig. 4). The residual amount of PUT.2HCl also decreased exponentially over time, but the decline was not as pronounced as with AA (Fig. 4).
At Day 0 (1 hr outdoor exposure), the quantity of AA extracted from the 3C cone lure averaged 3.6422 ± 0.1579 g. This value is significantly lower than the intended manufacturer amount of 5.0 g (APHIS-CPHST-TIML-SOP-109 2018). The specified manufacturer amount of PUT.2HCl in the 3C lure is intended to be 0.55 g. Instead, methanol extraction of the lures indicated an average of only 0.3055 ± 0.0817 g PUT.2HCl. The manufacturer amount of TMA in the 3C lure is 1.5 g; however, only 0.7357 ± 0.0888 g was recovered by total content extraction. A freshly opened set of lures, not exposed to outdoor conditions, showed even lower values for AA and TMA.HCl, 2.8613 ± 0.2763 g and 0.5610 ± 0.1132 g, respectively. Analysis of PUT.2HCl indicated an average of 0.3496 ± 0.1068 g upon immediate extraction (Table 1).
As with the 2C lure, an exponential decay pattern was observed for all analytes contained in the 3C cone lure (Fig. 5), but the decline in AA was more subtle than in the 2C cone lure. The residual amount of AA dropped sharply during the first four weeks of field exposure, then stabilized at a consistent level from weeks 5-8, with an average of 0.8617 ± 0.5232 g AA remaining at week 8 (Fig. 5). The residual amount of PUT.2HCl declined gradually up through week 4, then leveled off to an average of 0.1924 ± 0.0694 g detectable at week 8 (Fig. 5). Of all the analytes, TMA displayed the sharpest decline in residual content upon field exposure. There was a very steep decline during the initial two weeks, followed by a stable low level of TMA from weeks 3 to 8 ending with an average content of 0.0304 ± 0.0022 g (Fig. 5).
Optimal monitoring strategies for pest tephritids, including Anastrepha spp., should focus on female-targeted trapping systems compatible with sterile male release programs. If monitoring traps capture male flies, this could potentially lower the flooding ratio and thereby reduce the likelihood that a sterile male will encounter, and mate with, a female. As supported by the field results presented here and in previous studies (Epsky et al. 1999, Jang et al. 2007, Kendra et al. 2008, Shelly et al. 2020) both hydrolyzed TY (a proteinaceous liquid bait) and synthetic protein-based lures are effective for preferential attraction of females. This behavioral response is a direct result of females being sexually immature at eclosion (anautogenous), requiring high protein meals for completion of ovary maturation and egg development (vitellogenesis and oogenesis) (Kendra et al. 2006). Thus, females are highly attracted to the volatiles from torula yeast because they likely signal a source of protein, similar to ammonium acetate, putrescine, and trimethylamine.
The torula yeast bait is potentially more attractive to protein-seeking flies because it produces higher concentrations of attractive volatiles than the synthetic commercial lures. Torula yeast also likely contains unidentified attractive volatiles to protein-seeking adult flies. The suite of these attractive volatiles in TY may also interact additively or synergistically for increased attraction compared to ammonia acetate and putrescine alone. Further, the TY solution was replaced each week so there was always a fresh source of protein feeding cues from this bait. Although TY typically captures more females, it has several drawbacks, including variability in chemical composition (Epsky et al. 2014), a short field life (Calkins et al. 1984), and high captures of nontarget species. Traps baited with TY captured 2–3 times more nontarget flies than synthetic lures in our field trials. When considering the most appropriate lure for a tephritid monitoring program, trade-offs like attraction and bycatch must be considered (Navarro-Llopis et al. 2008).
Consequently, both APHIS (USDA 2015) and State regulatory agencies, for example, the California Department of Food and Agriculture (CDFA 2013), currently utilize protein-based synthetic lures in surveillance programs for female tephritid pests. Due to the advantages of handling and ease-of-deployment in Multilure traps, the solid matrix cone lures are preferred over the previous BioLure formulations. However, there have been few rigorous field evaluations of the cone lures to date. Jang et al. (2007) tested the newly developed cone lures against BioLure and TY in Florida using release-recapture tests with A. suspensa and C. capitata (ground and aerial releases of sterile lab-reared flies, male and female). With A. suspensa, the results were mixed; in one test, the 2C and 3C BioLures captured more A. suspensa than the 3C cone lure, and the 2C BioLure captured more than TY. In the second test, captures with the 3C BioLure, 3C cone lure, and TY were all comparable. With C. capitata, there were no differences in captures between the 3C BioLure and 3C cone lure (TY was not tested). More recently, Shelly et al. (2020) tested the 3C cone lure against TY for the capture of C. capitata and B. dorsalis in Hawaii. In field trials with wild populations, the 3C cone lure was more attractive than TY for C. capitata; however, with B. dorsalis, TY was more attractive. In a release-recapture experiment with laboratory reared flies, TY captured more of both species (Shelly et al. 2020).
To the best of our knowledge, the results presented here constitute the first evaluation of 2C and 3C cone lures versus TY liquid bait to capture feral A. suspensa in Florida. At all three field sites, the 2C cone was more attractive to A. suspensa than the 3C cone. This observation is consistent with the results obtained previously with 2C and 3C BioLures (Epsky et al. 2011). Addition of the trimethylamine component apparently has a repellent effect on A. suspensa. Previous laboratory studies with A. suspensa indicated that female age and physiological state affect both olfactory and behavioral responses to food-based cues, and dose is a critical factor (Kendra et al. 2005b, 2009). In particular, ammonia is known to be attractive to A. suspensa at low doses; however, it becomes repellent when presented at high doses, particularly for immature females (Kendra et al. 2005b). The concurrent presentation of AA and TMA may result in repellency with the 3C lures and account for the lower captures relative to the 2C lures.
Since the dose of food-based attractants has a significant effect on insect response, it is imperative that reliable analytical techniques be used to accurately quantify lure contents and subsequent release rates in the field. This study used ion chromatography methods (per APHIS-PPQ’s current quality control recommendations) to determine lure residual analyte content throughout an 8-wk field exposure period. These validated methods are more accurate than previous analyses based on Fourier Transformed Infrared Spectroscopy technique (FTIR) (Kendra et al. 2005a, Heath et al. 2007). Initial values of analytes in the 2C lures were similar to the values incorporated at manufacture. However, initial values in the 3C lures were consistently lower than the original amounts incorporated at manufacture. Since AA residuals are calculated from the response of the ammonium ion, it is possible that ammonia is lost by evaporation by the time a package is opened, or even beforehand, as packages are heat-sealed or may not be leak proof. Exposure to increased heat and humidity under field conditions for one hour (Day 0) revealed a slight increase in ammonia release compared to freshly opened lures. This could result from warm air and moisture interactions with the analytes, or within the cone matrix, allowing for matrix pores to open and release more analytes. Taken together, the increased attraction of 2C lures compared to 3C lures, the longer field longevity of 2C lures, and the quantification of residual contents over time, may all be important factors to assist regulatory agencies in designing appropriate monitoring programs for A. suspensa in Florida.
Ideally, the perfect fruit fly lure would contain one specific suite of components, at a specific ratio, that could be deployed by a regional crop protection program for the detection of multiple tephritid pest species (Thomas et al. 2008, Biasazin et al. 2018). However, as supported by these field trials and other published reports (Diaz-Fleischer et al. 2009), optimal pest monitoring systems for tephritids will require species-specific lures. Much attention has been focused on protein-based attractants for females; however, another potential approach to improve lure efficacy would be the incorporation of host-based attractants. Recently, fruit volatiles were found to be more attractive than TY for oviposition-ready oriental fruit flies (Roh et al. 2021). In other pest systems, host kairomones alone (Kendra et al. 2014, 2016a) or kairomones in synergistic combination with food-based attractants (Kendra et al. 2017) have been used successfully for the improvement of field lures.
We thank APHIS-PPQ for supplying the 2C and 3C cone lures used in this study; Teresa Narvaez, Monica Blanco, Amanda Perez-Castro, and Sean Brown (USDA-ARS, Miami, FL) for technical assistance; Herma Pierre and Richard A. King (USDA-APHIS-PPQ-S&T Treatment and Inspection Methods Laboratory, Miami, FL) for their method validation expertise, analytical support, and for providing the instrumentation for the residual analysis work; and Dong Cha (USDA-ARS, Hilo, HI) for providing a critical review of an earlier version of this manuscript. This work was supported in part by USDA-ARS Appropriated Funds (Project # 6038-22000-007-00D) and by an appointment to the ARS Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) (A. Vázquez), an interagency agreement between the U.S. Department of Energy (DOE) and the USDA, managed under DOE contract # DE-SC0014664. The opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the USDA, DOE, or ORISE. USDA is an equal opportunity provider and employer.
Anastrepha suspensa(Loew) (Diptera: Tephritidae) McPhail traps for survey and detection.
Anastrepha suspensa(Loew) (Diptera: Tephritidae), populations with McPhail traps.
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Anastrepha obliqua(Diptera: Tephritidae) individuals to MultiLure traps baited with BioLure or NuLure.
Anastrepha suspensato liquid protein baits and synthetic lure formulations, pp.
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Anastrepha suspensa(Diptera: Tephritidae) adults.
Anastrepha suspensa(Diptera: Tephritidae).
Ceratitis capitata(Diptera: Tephritidae) in seven countries.
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Anastrepha suspensa(Diptera: Tephritidae).
Anastrepha suspensa(Diptera: Tephritidae).
Anastrepha suspensa(Diptera: Tephritidae).
Anastrepha suspensa(Diptera: Tephritidae) to terminal diamines in a food-based synthetic attractant.
Anastrepha suspensa(Diptera: Tephritidae) to putrescine and ammonium bicarbonate lures.
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Xyleborus glabratus(Coleoptera: Curculionidae: Scolytinae).
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Anastrepha ludens(Diptera: Tephritidae): effects on attractiveness of proteinaceous and fruit-derived lures.
Anastrepha ludens, to a mixture of ammonia, methylamine, and putrescine.
Staphylococcus aureuscultures for Mexican fruit fly,
Anastrepha ludens.
Anastrepha ludens.
Anastrepha ludens(Diptera: Tephritidae).
Anastrepha suspensa(Diptera: Tephritidae).
Anastrepha ludens(Diptera: Tephritidae).
Anastrephafruit flies (Diptera: Tephritidae).
Anastrephafruit flies (Diptera: Tephritidae).
Anastrepha suspensa(Diptera: Tephritidae) trapping in the Dominican Republic.