Trapping tephritid fruit flies (Diptera: Tephritidae) in citrus groves of Fujian Province of China

Certain tephritid fruit flies, such as the oriental fruit fly, Bactrocera dorsalis, the Chinese citrus fly, B. minax and the Japanese orange fly, B. tsuneonis (Diptera: Tephritidae: Dacinae), are destructive citrus pests in China. A two-year trapping study was conducted in pomelo, Citrus maxima, groves in Fujian Province of China. The objectives of this study were to investigate the species, the abundance of tephritid fruit flies in the orchards, as well as the efficacy of the selected lure traps to these flies. Four lure traps or devices, i.e. methyl eugenol + Steiner trap (ST), cuelure + ST, ammonium acetate + putrescine + ST, and sticky spheres, were deployed from June to November 2017 and April to October 2018. Six economically significant Dacini pests were trapped during the period. These flies are B. dorsalis, the melon fruit fly, Zeugodacus cucurbitae, the pumpkin fruit fly, Z. tau, the Malaysian fruit fly, B. latifrons, and other two species - B. rubigina and Z. scutellatus. B. dorsalis was the most abundant, accounting for more than 50% of the capture, followed by Z. cucurbitae. The remaining four species accounted for less than 2% of the total capture. B. minax and B. tsuneonis, two destructive citrus-damaging tephritid fruit flies in China, were not found during the trapping period. Methyl eugenol trapped the highest number of fruit flies, followed by cuelure.     

Fruit fly (Diptera: Tephritidae) diversity in cucurbit fields and surrounding forest areas of Himachal Pradesh,a north-western Himalayan state of India

During the course of studies, Bactrocera (Bactrocera) latifrons (Hendel), B. (B.) nigrofemoralis White and Tsuruta, Dacus (Callantra) longicornis Wiedemann, Dacus (Callantra) sphaeroidalis (Bezzi), Cyrtostola limbata (Hendel) and Pliomelaena udhampurensis Agarwal and Kapoor were recorded for the first time in Himachal Pradesh in a cucurbit ecosystem. Apart from these, other species viz. Bactrocera tau, Bactrocera cucurbitae, Bactrocera dorsalis, Bactrocera zonata, Bactrocera scutellaris, Bactrocera diversa and Dioxyna sororcula (Wiedemann) were also identified. Distribution records of B. (B.) dorsalis (Hendel), B. (B.) zonata (Saunders), Bactrocera (Hemigymnodacus) diversa (Coquillett), B. (Zeugodacus) cucurbitae (Coquillett), B. (Z.) scutellaris (Bezzi) and B. (Z.) tau (Walker) has been described.     

Host status of ‘Scifresh’ apples to the invasive fruit fly species Bactrocera dorsalis,Zeugodacus cucurbitae,and Ceratitis capitata (Diptera: Tephritidae)

We conducted no-choice cage and field infestation studies to determine if the fruit of apples (Malus x domestica L., ‘Scifresh’) are hosts for three invasive tephritid fruit fly species that may enter New Zealand or other apple growing areas. In screen cage tests, punctured and unpunctured (intact) fruit of ‘Scifresh’ apples were exposed to gravid females of Bactrocera dorsalis (Hendel) (Oriental fruit fly), Zeugodacus (Bactrocera) cucurbitae (Coquillet) (melon fly), or Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), outdoors for 24 h and then held on sand in the laboratory for four weeks for pupal development and adult emergence. Unpunctured fruit produced an average of 269.4, 4.3 and 70.1 puparia per kg of fruit for B. dorsalis, Z. cucurbitae and C. capitata, respectively. Punctured fruit produced an average of 619.4, 0.8 and 129.5 puparia per kg of fruit for B. dorsalis, Z. cucurbitae and C. capitata, respectively. By comparison, unpunctured and punctured papaya fruit (Carica papaya, ‘Rainbow’, a preferred host) produced 206–675 and 464–735 puparia per kg of fruit, respectively, across all species. In general, the average weight of individual fruit fly puparia from apple was significantly less (41–71%) than that of puparia reared from papaya, and development times were slower on apple than on papaya. Overall, ‘Scifresh’ apples were a moderately good host for B. dorsalis and C. capitata, and a very poor host for Z. cucurbitae in cage tests. Field exposure of ‘Scifresh’ apples suspended from papaya trees resulted in no infestation by B. dorsalis or Z. cucurbitae under natural conditions. This information will help to inform decisions about quarantine restrictions and potential crop loss in the event of incursions of these fruit flies into apple-producing countries.     

Jackson trap efficiency capturing Bactrocera dorsalis and Zeugodacus cucurbitae with male lures with and without insecticides

Jackson traps baited with male lures with or without insecticides are essential components of surveillance and monitoring programmes against pest tephritid fruit flies. The ability of a trap to capture a fly that enters, sometimes termed ‘trap efficiency’, is dependent on many factors including the trap/lure/toxicant combination. We tested the effects of three important components of Jackson traps on efficiency of capture of two important fruit fly species, using the ‘standard’ (i.e. as they are used in the state-wide surveillance programme in California) and alternative setups: Insecticide (Naled, DDVP or None), type of adhesive on the sticky panel (Seabright Laboratories Stickem Special Regular or Stickem Special HiTack) and use of a single or combination male lure (Methyl eugenol and/or cuelure). Experiments were conducted in large outdoor carousel olfactometers with known numbers of Bactrocera dorsalis and Zeugodacus cucurbitae and by trapping wild populations of the same two species. Lures were aged out to eight weeks to develop a comprehensive dataset on trap efficiency of the various combinations. Results indicate that the current liquid lure/naled combinations on cotton wicks used in California for surveillance of these flies can be effectively replaced by plastic polymer plugs for the lure and pre-packaged DDVP strips with no loss of trap efficiency for eight weeks of use or longer. The ‘high tack’ adhesive showed no advantage over the current standard against these flies, and both have low efficiency when used without an insecticide in the trap. Combination lure + DDVP varied when compared to the current standard liquid lure + naled: Olfactometer assays showed similar efficiency between them for B. dorsalis, but higher efficiency for the wafer against Z. cucurbitae. Field result showed similar or slightly higher performance of the wafer compared with the standard for B. dorsalis, but a much lower catch of Z. cucurbitae.     

Synergistic and additive interactions among components of food-based baits underlie female fruit fly attraction

Attraction of tephritid fruit flies to some food sources can be enhanced by the presence of ammonia derivatives, compounds that are perceived as volatile cues for protein-rich food sources. Using a comparative approach, we (1) evaluated the behavioral responses of females of three invasive fruit fly species, Bactrocera (Zeugodacus) cucurbitae (Coquillett), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) (all Diptera: Tephritidae) to trub (a protein-rich waste brewer’s yeast product generated during the production of beer), Concord grape juice (a protein-deficient material), and ammonium acetate, and (2) identified synergistic and additive interactions between low- and high-attractiveness materials and ammonium acetate. We established the attractiveness of fresh trub, grape juice, and ammonium acetate when tested singly to females of all three fly species. Although ammonium acetate did not enhance significantly the response of females of any species to fresh trub, the most attractive material, ammonium acetate, did significantly enhance females’ level of response to aged trub (a comparatively less attractive material) and to grape juice. Our research found a synergistic interaction between diluted grape juice and ammonium acetate for B. cucurbitae, as well as between aged trub and ammonium acetate for B. dorsalis. For C. capitata, additive effects among food attractants and ammonium acetate were identified. Our findings increase our understanding of fruit fly female olfactory-driven behavior in response to food-based materials and the extent to which ammonium acetate modulates female response to protein-rich and protein-deficient materials.     

Canola,corn, and vegetable oils as alternatives for wheat germ oil in fruit fly larval diets

Four wheat germ oil alternatives (corn oil, vegetable oil, canola oil with 10% vitamin E, and canola oil with 20% vitamin E), purchased from a local supermarket in Hawaii, were added to a fruit fly liquid larval diet as a replacement for wheat germ oil in the rearing of fruit fly larvae. The oils were tested on three species of fruit flies in Hawaii, Ceratitis capitata (TSL strain), Bactrocera dorsalis, and Bactrocera cucurbitae. They were evaluated for their efficacy in replacing WGO, based on: pupal recovery (%), larval duration (d), pupal weight (mg), adult emergence (%), adult fliers (%), mating (%), egg production per female per day, egg hatch (%), and peak egging period (d). Diets with WGO and without any oil were used as controls. The objective of the study was to select the most cost effective alternative oils with the best performance to replace the currently used WGO, which is pricey and hard to find. The results showed that there was no significant difference in performance among the tested oils in B. cucurbitae and B. dorsalis as regards the above mentioned parameters. Lower mating rate was observed in B. cucurbitae from those reared in vegetable oil and canola oil (10% vitamin E) diet. Lower egg production and egg hatch were obtained with B. dorsalis whose larvae were reared in vegetable and canola oil (both 10% and 20% vitamin E). Vegetable oil diet seemed to reduce pupal weight, shorten larval duration, and increase pupal recovery of C. capitata. The results suggest that WGO can be substituted with corn oil, vegetable oil, or canola oils for B. cucurbitae, while corn oil is a better alternative for B. dorsalis, and vegetable oil is best for C. capitata.     

Population genetic structure of Zeugodacus tau species complex in Thailand

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Competitive Interactions between Immature Stages of Bactrocera cucurbitae (Coquillett) and Bactrocera tau (Walker) (Diptera: Tephritidae) under Laboratory Conditions

The melon fly, Bactrocera cucurbitae (Coquillett), and the pumpkin fly, Bactrocera tau (Walker), are economically important pests that attack mainly cucurbitacean fruits. The two fruit fly species have similar natural distributions, host ranges, and population growth capacities. This study was designed to assess the asymmetrical competitions through resource exploitation between the larvae of B. cucurbitae and B. tau at different density levels and temperatures, and on different hosts by comparing the relative effects of interspecific and intraspecific interactions on four life history parameters: survival rate, puparial mass, puparial duration, and developmental duration. Our results showed that intraspecific and interspecific competitions occurred under some laboratory conditions, and B. cucurbitae took advantage over B. tau at the high-density level and at low and high temperatures on pumpkin, bitter gourd, and bottle gourd when interspecific competition took place. Intraspecific and interspecific competitions mainly affected the puparial mass and the survival rate of the two fruit fly species but had no marked effect on the puparial duration or development duration.     

Allyl‐2,6‐dimethoxyphenol,a female‐biased compound,is robustly attractive to conspecific males of Bactrocera dorsalis at close range

Insect cuticular hydrocarbons (CHCs) play important roles in mate recognition and chemical communication. To explore the cues regulating courtship and mating behaviour in the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), CHCs were extracted from mature virgin female and male oriental fruit flies using n‐hexane. Nine compounds – i.e., 4‐allyl‐2,6‐dimethoxyphenol (designated ‘compound 3’) and eight ester compounds – had significantly greater abundance in female samples than in males. Of these nine compounds, six (1, 2, 4, 5, 6, and 8) elicited electrophysiological responses from the antennae of male flies. Compound 3 did not elicit a detectable male antennal response, but in Y‐tube olfactometer bioassays, it exhibited robust attractiveness to conspecific males at close range. We speculate that compound 3 is a close‐range sex pheromone in B. dorsalis. A mating competition experiment revealed that compound 3 significantly increased the competitiveness of males, which implied that compound 3 might be used in control programs of B. dorsalis.     

Localization of mating behavior of releasedBactrocera dorsalis flies on host fruit in an orchard

Oriental fruit flies,Bactrocera dorsalis, cultured in the laboratory for six generations, were released when 12–14 days old in an orchard of nonfruiting host trees that were furnished with either food and water, nonpunctured host fruit, punctured host fruit, or no resources. Nearly all flies of both sexes, all sexual behavior of males, and all mating pairs were observed on trees with fruit. Moreover, on trees with fruit, nearly all flies of both sexes, nearly all sexual behavior of males, and nearly all mating pairs occurred on the fruit itself rather than on the foliage or branches. In a subsequent test, both sexes were found to be strongly attracted to the odor of host fruit. For a polyphagous species of a tropical tephritid, these findings are the first to show a high level of male aggregation and a high amount of male sexual behavior on the fruit of host trees. Findings are discussed in relation to current knowledge of tephritid mating behavior. An additional quality-control test for laboratory cultured males used in the sterile insect technique of fly management is recommended.     

Effects of temperature on the fecundity and longevity of Zeugodacus cucurbitae (Coquillet) (Diptera: Tephritidae) on artificial diet

The melon fruit fly, Zeugodacus cucurbitae (Coquillett), is an important polyphagous pest that damages to various agricultural crops, whose distribution has become global as a result of human activity. In this study, we investigated the fecundity, pre-oviposition and oviposition periods, and the longevity of adult Z. cucurbitae at various constant temperatures ranging from 15 to 35.2°C. One newly emerged one virgin female and two males of Z. cucurbitae were used, and the longevity of both sexes and the fecundity of the females were examined daily. The longevity of female Z. cucurbitae ranged from 183.8 days at 15.0°C to 30.8 days at 35.2°C, and the maximum fecundity per female was 1204 eggs at 24.5°C. The lower development threshold (LDT) and thermal constant (K) of females were estimated as 14.8°C and 781.13 degree-days, respectively. Female reproduction was modeled using a two-phase oviposition model. Oviposition was estimated using females in the oviposition phase, which had a complete pre-oviposition phase. The oviposition model consisted of two reproductive components (total fecundity and age-specific cumulative oviposition rate during oviposition) and a survival component (age-specific survival rate). The daily egg production of Z. cucurbitae was estimated in relation to adult age and temperature.     

Fluctuations in fruit fly abundance and infestation in sweet gourd fields in relation to varied meteorological factors

The study was conducted with the aim of furthering our understanding of seasonality in the population dynamics and infestation rates of the fruit fly Bactrocera spp. in sweet gourd (Cucurbita moschata) during winter and summer in 2017. We also investigated the effects of using methyl eugenol traps on fly abundance and infestation. Two fruit fly species, namely, B. cucurbitae and B. dorsalis, were present in the sweet gourd field, and we observed fluctuations in their abundance. Compared to B. dorsalis, B. cucurbitae was significantly more abundant in both winter and summer. Infestation level was found to be the highest in fields lacking methyl eugenol traps in both seasons. Fruit fly larval population per infested fruit was higher in summer than in winter. Fly abundance was significantly and positively correlated with mean temperature and rainfall but significantly and negatively correlated with light intensity. Relative humidity was insignificantly but positively correlated with fly abundance. The temperature, light intensity, relative humidity, and rainfall individually explained 48.9, 24.1, 0.8, and 1.6% of variation in fruit fly abundance, respectively. The combined effect of the weather parameters on fruit fly abundance was 75.4% and was significant predictor of fruit fly abundance.     

Comparative demography of a specialist and generalist fruit fly: Implications for host use and pest management

Host plants used by phytophagous insects can have significant consequences on demography parameters, overall lifetime fitness and their subsequent population dynamics. Here, we conduct a comparative demographic study between the specialist Zeugodacus cucumis (French) and generalist Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) to determine whether the host plants used by these fly species play any role in their overall lifetime fitness and explains current host use patterns. These two fly species are pests within the north-eastern region of Australia and we further aimed to use complete life-history data to determine the population parameters and models that would help identify the sensitive life-history stage that could be targeted for effective field management. Eggs collected from laboratory-reared flies were inoculated into organically grown fruits of both the primary and alternate host plant cultivars of both fly species. The proportion surviving each life stage from egg through to adult and fecundity were monitored for all cohorts from the different plant cultivars. Complete stage-base life-tables for cohorts of each fly species developing from each fruit cultivar were constructed, and the key demographic parameters and population models were analysed using PopTools matrix model programme. Our results showed that the host used by each fly species had significant consequences on fly demographic parameters and hence their overall lifetime fitness. The generalist B. tryoni was able to compensate for the fitness loss experienced at the pre-adult stage by having adults with higher fecundity, but this was not the case for the specialist Z. cucumis. Stage-base population models revealed that the population growth rate of both species was highly sensitive at the adult reproductive stage, indicating that manipulating probability of survival at this life stage would effectively manage populations of these pest species. This study provides the empirical evidence of undertaking complete life history demography studies of phytophagous insects to accurately understand their lifetime fitness consequences of using a certain host, their observed host use patterns, and overall population dynamics. We suggest that any efforts to manage dacine fruit fly pest population should consider life-history consequences of host use.     

A review of the current knowledge on Zeugodacus cucurbitae (Coquillett) (Diptera,Tephritidae) in Africa,with a list of species included in Zeugodacus

This paper reviews all available information regarding the occurrence and biology of the melon fly, Zeugodacus cucurbitae (Coquillett), in the Afrotropical Region, including data on invasion history, distribution patterns, population genetics, host range, and interspecific competition. Although limited intraspecific variability has been observed within the region regarding the above mentioned aspects, there seems to be no indication that Zeugodacus cucurbitae represents a species complex. A checklist of all of the species included in Zeugodacus as recently proposed by Virgilio et al. (2015) is provided.     

Laboratory evaluation of the chemosterilant lufenuron against the fruit flies Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons

Four species of tephritid fruit flies, Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons were evaluated for toxic, developmental, and physiological responses to the chemosterilant lufenuron. No significant mortality of laboratory strains of the first three species was observed after their exposure up to 50 μg/mL of lufenuron in agar adult diet, whereas B. latifrons adults fed with 50 μg/mL of lufenuron in the diet caused significant mortality compared to the control. Fertility of C. capitata adults fed on 50 μg/mL lufenuron-fortified diet between 7 and 12 days of age was approximately 46% of the no lufenuron control. Fertility of B. dorsalis and B. latifrons adults fed on 50 μg/mL lufenuron-incorporated diet was about 45% and 62% of the control, respectively. Lufenuron did not significantly affect fertility of B. cucurbitae adults. Lufenuron did not affect fecundity of C. capitata and B. dorsalis. Fecundity of B. cucurbitae and B. latifrons was not evaluated due to difficulty to count the eggs laid deep in the agar diet. Larvae fed on a liquid larval diet with ≤ 0.1 μg/mL of lufenuron were also evaluated. Pupal recovery, adult emergence, adult fliers, mating, egg hatch, and egg production of C. capitata were significantly decreased, while for B. dorsalis, pupal recovery, larval duration and adult emergence were affected. No effect of lufenuron on B. cucurbitae larvae was observed. B. latifrons was not performed because shortage of eggs at the time of this research. Lufenuron is a potential agent for management and control of C. capitata and B. dorsalis.     

Biology of Bactrocera (Zeugodacus) tau (Walker) (Diptera: Tephritidae)

The biology of the fruit fly Bactrocera tau, an important horticultural pest, was studied under laboratory conditions at 25°C and 60–70% relative humidity on Cucurbita maxima. The duration of mating averaged 408.03 ± 235.93 min. After mating, the female fly had a preoviposition period of 11.7 ± 4.49 days. The oviposition rate was 9.9 ± 8.50 eggs and fecundity was 464.6 ± 67.98 eggs/female. Eggs were elliptical, smooth and shiny white, turning darker as hatching approached, and measured 1.30 ± 0.07 mm × 0.24 ± 0.04 mm. The chorion has polygonal microsculpturing and is species-specific with polygonal walls. The egg period lasts for 1.3 ± 0.41 days. The duration of the larval period is 1.2 ± 0.42, 1.7 ± 0.48 and 4.0 ± 0.94 days for first, second and third instars, respectively. Pupation occurs in the sand or soil and pupal periods are 7.0 ± 0.47 days. The life cycle from egg to adult was completed in 14.2 ± 1.69 days; the longevity of mated females and males was 130.33 ± 14.18 and 104.66 ± 31.21 days, respectively. At least two to three generations were observed from June 2008 to June 2009.     

Real‐time PCR assays for rapid detection of Zeugodacus cucumis and Bactrocera jarvisi (Diptera: Tephritidae) for quarantine application

Zeugodacus cucumis and Bactrocera jarvisi are pests of fruit and vegetable crops and cause damage to horticulture industries. Immature stages of these two fruit fly species have been intercepted in New Zealand a number of times. Identification to species was not possible using morphological characters; thus, it is important to develop an assay for their species‐level identification. Here, the real‐time PCR assays for rapid identification of Z. cucumis and B. jarvisi were developed and validated. The PCR protocols demonstrated their specificity by amplifying the two target species successfully, with no cross‐reactions observed in the tested tephritid species. The in silico test of the primer and probe binding sites of the two assays also demonstrated the assays’ specificity by no mismatches present in the binding regions of the target species, but 1–4 mismatches in the binding regions of the non‐target fruit fly species. The thresholds of detection for the two assays are as low as 10 copies/µl of the target DNA, indicating that the assays have a very high sensitivity. The application of the real‐time PCR assays has greatly assisted in routine pest identifications at the New Zealand border and surveillance programme. Therefore, the assays have the potential to be used by diagnostic agencies and research organizations worldwide.     

Polymorphic microsatellite DNA markers in Bactrocera cacuminata (Hering) (Diptera: Tephritidae)

Bactrocera cacuminata (Hering) is a nonpest member of the Bactrocera dorsalis complex offering a platform to check hypotheses extrapolated from the more studied pest species. Six polymorphic microsatellite loci were isolated from enriched genomic libraries constructed using a biotin/streptavidin capture protocol. Allele number varied between three and nine; the expected heterozygosity ranged between 0.29 and 0.81. No significant deviations from Hardy–Weinberg equilibrium or linkage disequilibrium were found. These microsatellite markers have potential to be used to examine population structure and mating systems in this tropical fruit fly.     

Cuticular hydrocarbons from six species of tephritid fruit flies

Cuticular alkanes obtained from larvae and adults of six species of tephritid fruit flies, Anastrepha ludens, A. suspensa, Ceratitis capitata, C. rosa, Dacus cucurbitae, and D. dorsalis were analyzed by gas chromatography. The same four major alkanes were shown to be present by capillary GC-mass spectra in all Anastrepha and Ceratitis larvae. Profiles were obtained from individual larvae and adult specimens that showed statistical differences between species, whereas profiles of conspecific life forms including pupae of A. suspensa from different locations showed some similarities. Sexual dimorphism was not observed in alkanes extracted from adults. A novel series of alkadienes was found in all Anastrepha and Ceratitis but not in Dacus.     

Effects of depth of oviposition dish and age ofrearing host on efficiency of mass production of thetephritid fruit fly parasitoid Psyttaliafletcheri

Psyttalia fletcheri is a solitary larval endoparasitoid ofthe melon fruit fly, Bactrocera cucurbitae. Initiallycolonized in 1985, mass production of P.fletcheri for the last 10 years has beenfacilitated with a rearing method developed earlier.However, the level of parasitoid recovery seldomexceeded 35%. We examined the parasitoid'sdevelopmental biology and behavior to identify theprocedures that may improve efficiency ofproduction. We found that by limiting the depth ofoviposition dish (receptacle that holds the hostlarvae during exposure to female parasitoids) to 4 mm and using 4-d-old (late 2nd instar) B.cucurbitae larvae for oviposition, parasitoid yieldwas increased two-fold.