Sieving Fruit Pulp to Detect Immature Tephritid Fruit Flies in the Field.

Fruit flies of the Tephritidae family are among the most destructive and invasive agricultural pests in the world. Many countries undertake expensive eradication programs to eliminate incipient populations. During eradication programs, a concerted effort is made to detect larvae, as this strongly indicates a breeding population and helps establish the spatial extent of the infestation. The detection of immature life stages triggers additional control and regulatory actions to contain and prevent any further spread of the pest. Traditionally, larval detection is accomplished by cutting individual host fruits and examining them visually. This method is labor intensive, as only a limited number of fruit can be processed, and the probability of missing a larva is high. An extraction technique that combines i) mushing host fruit in a plastic bag, ii) straining pulp through a series of sieves, iii) placing retained pulp in a brown sugar water solution, and iv) collecting larvae that float to the surface was tested. The method was evaluated in Florida with field-collected guava naturally infested by Anastrepha suspensa. To mimic low populations more representative of a fruit fly eradication program, mangos and papaya in Hawaii were infested with a known, low number of Bactrocera dorsalis larvae. The applicability of the method was tested in the field on guava naturally infested by B. dorsalis to evaluate the method under conditions experienced by workers during an emergency fruit fly program. In both field and laboratory trials, mushing and sieving the pulp was more efficient (required less time) and more sensitive (more larvae found) than cutting fruit. Floating the pulp in brown sugar water solution helped detect earlier instar larvae. Mushing and sieving fruit pulp of important tephritid hosts may increase the probability of detecting larvae during emergency programs.

Harmonic radar tracking of individual melon flies, Zeugodacus cucurbitae, in Hawaii: Determining movement parameters in cage and field settings.

Tephritid fruit flies, such as the melon fly, Zeugodacus cucurbitae, are major horticultural pests worldwide and pose invasion risks due primarily to international trade. Determining movement parameters for fruit flies is critical to effective surveillance and control strategies, from setting quarantine boundaries after incursions to development of agent-based models for management. While mark-release-recapture, flight mills, and visual observations have been used to study tephritid movement, none of these techniques give a full picture of fruit fly movement in nature. Tracking tagged flies offers an alternative method which has the potential to observe individual fly movements in the field, mirroring studies conducted by ecologists on larger animals. In this study, harmonic radar (HR) tags were fabricated using superelastic nitinol wire which is light (tags weighed less than 1 mg), flexible, and does not tangle. Flight tests with wild melon flies showed no obvious adverse effects of HR tag attachment. Subsequent experiments successfully tracked HR tagged flies in large field cages, a papaya field, and open parkland. Unexpectedly, a majority of tagged flies showed strong flight directional biases with these biases varying between flies, similar to what has been observed in the migratory butterfly Pieris brassicae. In field cage experiments, 30 of the 36 flies observed (83%) showed directionally biased flights while similar biases were observed in roughly half the flies tracked in a papaya field. Turning angles from both cage and field experiments were non-random and indicate a strong bias toward continued "forward" movement. At least some of the observed direction bias can be explained by wind direction with a correlation observed between collective melon fly flight directions in field cage, papaya field, and open field experiments. However, individual mean flight directions coincided with the observed wind direction for only 9 out of the 25 flies in the cage experiment and half of the flies in the papaya field, suggesting wind is unlikely to be the only factor affecting flight direction. Individual flight distances (meters per flight) differed between the field cage, papaya field, and open field experiments with longer mean step-distances observed in the open field. Data on flight directionality and step-distances determined in this study might assist in the development of more effective control and better parametrize models of pest tephritid fruit fly movement.

Flight Burst Duration as an Indicator of Flight Ability and Physical Fitness in Two Species of Tephritid Fruit Flies.

We introduce a method to quantify flight ability and physical fitness of individual fruit flies which we term 'Flight Burst Duration' (FBD). This consisted of tethering individual insects by the dorsal thorax using a vacuum and measuring the length of time the insect beats its wings while suspended off a surface. Consecutive measurements with Bactrocera dorsalis Hendel (Dipera: Tephritidae) and Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae) in the same day and across days indicated that a single measurement was sufficient, and that FBD was consistent and repeatable. Insects under stress from starvation displayed shorter FBD over time, and we suggest that the measure also relates to the physical condition or survival fitness of the individual. Though somewhat laborious and time-consuming, we propose that FBD can be useful for research studies requiring individual-level phenome data and for obtaining estimates quality and dispersive movement for insects.

A field test on the effectiveness of male annihilation technique against Bactrocera dorsalis (Diptera: Tephritidae) at varying application densities.

Male Annihilation Technique (MAT) is a key tool to suppress or eradicate pestiferous tephritid fruit flies for which there exist powerful male lures. In the case of Bactrocera dorsalis (Hendel), a highly invasive and destructive species, current implementations of MAT utilize a combination of the male attractant methyl eugenol (ME) and a toxicant such as spinosad ("SPLAT-MAT-ME") applied at a high density with the goal of attracting and killing an extremely high proportion of males. We conducted direct comparisons of trap captures of marked B. dorsalis males released under three experimental SPLAT-MAT-ME site densities (110, 220, and 440 per km2) near Hilo, Hawaii using both fresh and aged traps to evaluate the effectiveness of varying densities and how weathering of the SPLAT-MAT-ME formulation influenced any density effects observed. Counterintuitively, we observed decreasing effectiveness (percent kill) with increasing application density. We also estimated slightly higher average kill for any given density for weathered grids compared with fresh. Spatial analysis of the recapture patterns of the first trap service per replicate x treatment reveals similar positional effects for all grid densities despite differences in overall percent kill. This study suggests that benefits for control and eradication programs would result from reducing the application density of MAT against B. dorsalis through reduced material use, labor costs, and higher effectiveness. Additional research in areas where MAT programs are currently undertaken would be helpful to corroborate this study's findings.

Raspberry Ketone Trifluoroacetate Trapping of Zeugodacus cucurbitae (Diptera: Tephritidae)in Hawaii.

Melon fly, Zeugodacus cucurbitae (Coquillett), is a serious pest of tropical horticulture, causing damage to cucurbits, other fruiting vegetables, and certain tree fruits. The deployment of male lures comprises an important component of several detection and control strategies for this pest, with the main male attractant currently in use being cuelure (CL). A novel fluorinated analog of CL, raspberry ketone trifluoroacetate (RKTA), has been developed for the control of Bactrocera tryoni, a related pest; here, we test this compound for attraction to Z. cucurbitae. In outdoor screen cage testing, observations showed both more flies on filter papers, and a higher percentage of flies feeding, on papers treated with RKTA than on those with CL or melolure (ML). Field trapping with both yellow sticky traps and bucket traps found that RKTA captured more flies during the first 6 h of trapping than CL, while trap captures in the subsequent 18 h did not differ between the two lures. When comparing combined 24 h trap captures, yellow sticky traps containing RKTA captured more flies than those with CL, while bucket trap captures did not vary by lure. Analysis of lures weathered on filter paper found that nearly all applied RKTA hydrolyzed to RK within 6 h. Fine-scale melon fly behaviors digitally recorded in the field showed median resting distances from the lure of responding flies were shorter for RKTA than for CL. This study demonstrates the inherent attractiveness of RKTA while also highlighting the instability of this compound due to hydrolysis.

Cucumber Lure Trapping of Zeugodacus cucurbitae (Diptera: Tephritidae) in Hawaii and Taiwan: Longevity and Nontargets Captures.

The melon fly, Zeugodacus cucurbitae (Coquillett), is a serious pest of tropical horticulture, causing damage to cucurbits, tree fruits, and fruiting vegetables. Melon flies are especially attractive to freshly sliced cucumber, and this has led to the identification of a nine-compound kairomone lure that can be used to trap both female and male flies. In this study, a seven-compound lure, containing (Z)-6-nonenal, (Z)-6-nonen-1-ol, 1-octen-3-ol, (E,Z)-2,6-nonadienal, (E)-2-nonenal, hexanal, and 1-hexanol, was formulated into PVC plugs (100 or 300 mg/plug) for field testing in wet traps. In Hawaii, 100 mg of the seven-compound cucumber lure, loaded in either plugs or glass capillaries, attracted more flies than traps containing Solulys protein over a 9-wk period. However, both cucumber lure formulations showed marked declines in the number of flies trapped after 3 wk. Similar results were obtained during a 6-wk field trial using 100 mg cucumber lure plugs in Taiwan. Increasing the cucumber lure loading rate to 300 mg/lure increased the effective trapping life of the attractant during a second 9-wk field trial conducted in Hawaii. The synthetic cucumber lure showed female-biased sex ratios in trap captures in the Taiwanese and second Hawaiian field trials. Protein lures captures were female-biased in all three field trials. Wet traps in Hawaii containing the cucumber lure were found to capture 25-30 nontarget insects/trap/week, less than half that captured with Solulys. Captured nontarget insects represented 37 families in 10 orders. The most common families caught were Ceratopogonidae (∼9 flies/trap) and Gryllidae (∼7 crickets/trap).

Disruption of Darna pallivitta (Lepidoptera: Limacodidae) by Conventional and Mobile Pheromone Deployment.

Identification of the Darna pallivitta (Moore) pheromone component n-butyl (E)-7,9-decadienoate (E7,9-10:COOn-Bu) has made it possible to investigate communication disruption to control this lepidopteran pest. Conventional communication disruption trials showed marked decreases in the mean number of male moths captured in E7,9-10:COOnBu-treated fields compared with control fields. For traps baited with E7,9-10:COOnBu, percent disruptions were 94.4% and 92.1% for septa (1 g pheromone/ha, 1-wk trial duration) and spirals (6 g pheromone/ha, 8-wk trial duration) respectively. For traps baited with virgin female moths, percent disruption was 73.3% using septa disruptors (1 g pheromone/ha, 1-wk trial duration). Mobile communication disruption using Bactrocera cucurbitae (Coquillett) as carriers for E7,9-10:COOn-Bu was evaluated in the following three areas: fly survivorship, attraction of male moths to treated flies, and moth disruption in a small-scale field trial. Topical application of E7,9-10:COOnBu showed no significant decrease in survivorship at 50 and 80 µg/fly. However, decreased survivorship was observed at 100 µg/fly and linear regression showed E7,9-10:COOnBu dose was significantly correlated with B. cucurbitae survivorship. Traps containing honey-pheromone-fed flies attracted and caught D. pallivitta over a 1-wk period, demonstrating the attractiveness of the carrier. Releasing E7,9-10:COOnBu-fed B. cucurbitae (∼2 g pheromone/ha, 1-wk trial duration) resulted in significantly reduced trap catches in treatment fields compared with control fields on the first 2 d of the field trial. Percent disruptions were 84.7% (day 1) and 56.0% (day 2). These results suggest that both conventional communication disruption and mobile communication disruption have potential to control D. pallivitta.

Performance of methyl eugenol + matrix + toxicant combinations under field conditions in Hawaii and California for trapping Bactrocera dorsalis (Diptera: Tephritidae).

The oriental fruit fly, Bactrocera dorsalis (Hendel) is a major pest of many fruit crops worldwide. Current detection programs by federal and state agencies in the United States use a grid of traps consisting of liquid methyl eugenol (lure) and naled (toxicant) applied to cotton wicks and hung inside the trap. In recent years efforts have been made to incorporate these chemicals into various solid-type matrices that could be individually packaged to reduce human exposure to the chemicals and improve handling. New solid formulations containing methyl eugenol and either naled or dichlorovinyl dimethyl phosphate toxicants were compared with the standard formulations on cotton wicks in large scale field evaluation in Hawaii. Two reduced risk toxicants (spinosad and Rynaxypyr) were also evaluated. In one test the solid lure-toxicant-matrix combinations were sent to California to be weathered under California climate conditions and then sent back to Hawaii for evaluation. The polymer matrices with lure and toxicant were found to be as attractive as baited wicks and have the same longevity of attraction regardless of being weathered in Hawaii or in California. The new ingestible toxicants were also effective, although further testing of these ingestible lure + toxicant + matrix products is necessary.

Ring-fluorinated analog of methyl eugenol: attractiveness to and metabolism in the oriental fruit fly, Bactrocera dorsalis (Hendel).

Oriental fruit fly, Bactrocera dorsalis (Hendel), males are highly attracted to the natural phenylpropanoid methyl eugenol (ME). They compulsively feed on ME and metabolize it to ring and side-chain hydroxylated compounds that have both pheromonal and allomonal functions. Side-chain metabolic activation of ME leading to (E)-coniferyl alcohol has long been recognized as a primary reason for hepatocarcinogenicity of this compound in rodents. Earlier, we demonstrated that introduction of a fluorine atom at the terminal carbon of the ME side chain significantly depressed metabolism and specifically reduced formation of coniferyl alcohol but had little effect on field attractiveness to B. dorsalis. In the current paper, we demonstrate that fluorination of ME at the 4 position of the aromatic ring blocks metabolic ring-hydroxylation but overall enhances side-chain metabolism by increasing production of fluorinated (E)-coniferyl alcohol. In laboratory experiments, oriental fruit fly males were attracted to and readily consumed 1,2-dimethoxy-4-fluoro-5-(2-propenyl)benzene (I) at rates similar to ME but metabolized it faster. Flies that consumed the fluorine analog were as healthy post feeding as ones fed on methyl eugenol. In field trials, the fluorine analog I was approximately 50% less attractive to male B. dorsalis than ME.

Evaluation of lure dispensers for fruit fly surveillance in New Zealand.

BACKGROUND: Fruit flies (Diptera: Tephritidae) represent a major biosecurity threat to the horticulture sector of New Zealand, which is entirely free of these invasive pests. A nationwide surveillance programme is conducted to ensure any incursion is detected as early as possible. A review of the lure dispensers used is reported here. RESULTS: Lure dispenser emission trials found that the currently used lure plugs release lure more slowly under New Zealand subtropical to temperate climates than wafer dispensers. Subsequent trapping experiments at high altitude in Hawaii (as a mimic of New Zealand meteorological and expected fruit fly ecological conditions) compared Lynfield traps baited with the existing lure plug dispensers and newer wafer dispensers. Catches of wild Oriental fruit flies, Bactrocera dorsalis (Hendel), were 9.5-fold higher with methyl eugenol wafers than with the plugs. Recaptures of sterile melon flies, Bactrocera cucurbitae (Coquillet), were 2.6-fold higher with cuelure wafers than with the plugs. Recaptures of sterile Mediterranean fruit flies, Ceratitis capitata Weid., were not significantly higher with trimedlure wafers than with the plugs. CONCLUSIONS: Release rate and trapping experiments found new lure dispensers differed in release rate characteristics from existing dispensers under temperate and subtropical conditions, and indicated some potential for improvement in surveillance efficacy.

Consumption and metabolism of 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene, a fluorine analog of methyl eugenol, in the oriental fruit fly Bactrocera dorsalis (Hendel).

Methyl eugenol (ME) is a natural phenylpropanoid highly attractive to oriental fruit fly Bactrocera dorsalis (Hendel) males. The flies eagerly feed on ME and produce hydroxylated metabolites with both pheromonal and allomonal functions. Side-chain metabolic activation of ME has long been recognized as a primary reason for hepatocarcinogenicity of this compound on rodents. In an attempt to develop a safer alternative to ME for fruit fly management, we developed a fluorine analog 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene (I), which, in earlier field tests, was as active to the oriental fruit fly as ME. Now we report that B. dorsalis males are not only attracted to, but also eagerly consume (up to approximately 1 mg/insect) compound I, thus recognizing this fluorinated benzene as a close kin of the natural ME. The flies metabolized the fluorine analog I in a similar fashion producing mostly two hydroxylated products, 2-(3-fluoro-2-propenyl)-4,5-dimethoxyphenol (II) and (E)-coniferyl alcohol (III), which they stored in rectal glands. However, the introduction of the fluorine atom at the terminal carbon atom of the double bond favors the ring hydroxylation over a side-chain metabolic oxidation pathway, by which coniferyl alcohol is produced. It also appears that fluorination overall impedes the metabolism: at high feed rate (10 mul per 10 males), the flies consumed in total more fluorine analog I than ME but were unable to metabolize it as efficiently as ME.

Field response of Mediterranean fruit fly (Diptera: Tephritidae) to ceralure B1: evaluations of enantiomeric B1 ratios on fly captures.

(-)-Ceralure B1 (ethyl-cis-5-iodo-trans-2-methylcyclohexane-1-carboxylate), a male attractant for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is significantly more attractive than trimedlure (tert-butyl esters of 4(5)-chloro-2-methylcyclohexane-1-carboxylate), the current standard male attractant used in detection programs. This article reports studies that compare the effectiveness of racemic ceralure B1, mixtures of racemic ceralure B1 and pure (-)-ceralure B1, and trimedlure in field tests conducted in Hawaii, Africa, and Spain with wild Mediterranean fruit flies and in Florida with sterile released Mediterranean fruit fly. Trapping results showed that doses of (-)-ceralure B1 of 87.5 and 75% are just as effective as the 98% (-)-ceralure B1 and the racemic form to be almost as attractive. In nearly all studies, the racemic ceralure B1 was significantly better than trimedlure. These studies suggest that the racemic ceralure B1 could be a viable replacement for trimedlure in areawide detection programs for Mediterranean fruit fly. Synthesizing racemic ceralure B1 instead of a specific stereoselective enantiomer of ceralure B1 would likely be more cost-effective to produce and also might be useful in control as well as detection of this pest.

Improved attractants for Mediterranean fruit fly, Ceratitis capitata (Wiedemann): responses of sterile and wild flies to (-) enantiomer of ceralure B1.

Tests were conducted on wild Mediterranean fruit flies, Ceratitis capiata (Wiedemann), in Hawaii, Italy, and Kenya, and on sterile released flies in Florida and California with a new male attractant, (-)-ceralure B1. Compared on an equal dosage basis, Mediterranean fruit fly males were significantly more attracted to the (-)-ceralure B1 than to trimedlure in each of the sites tested except for California. Compared with the standard commercial 2 g trimedlure plug, 10 mg applied on cotton wicks (Kauai) was as attractive to wild males as trimedlure after the first 2 d of the test but not after 7 d. At a dose of 40 mg (50 times less than in the 2-g plug), the (-)-ceralure B1 was significantly more attractive to male flies than the 2-g trimedlure plug for the first week of service (Florida) but not after 2 wk. Studies using released sterile flies in Florida confirm our previous work on the improved attraction of (-)-ceralure B1 (40 mg) over trimedlure. However, this trend did not hold up in a single test conducted in a residential area in California that did not show a significant difference in attraction using 20 mg of compound. Future refinements in synthesis and costs of this compound and increased availability and testing will be needed before any final evaluation in the field can be carried out.