Generic ionizing radiation quarantine treatments against fruit flies (Diptera: Tephritidae) proposed

Tephritid fruit flies comprise the most important group of quarantined pests of fresh produce. Most quarantine treatments of fresh agricultural commodities are directed against these pests, and considerable effort in detection, trapping, and population control is expended worldwide to prevent these pests from invading new territories. Ionizing radiation has been studied for 70 yr for its possible use as a quarantine treatment against fruit flies, but has only been applied commercially on a limited basis since 1995. The treatment has great potential and will probably be used extensively in the future as it is tolerated by more species of fruits than any other major treatment. The U.S. Department Agriculture, Animal and Plant Health Inspection Service only recently proposed allowing irradiation for fresh agricultural imports from other countries, and other countries are studying proposals to do likewise. In 1991, the International Consultative Group on Food Irradiation recommended a generic dose against all tephritid fruit flies of 150 Gy. This article examines the literature dealing with irradiation quarantine treatments against fruit flies and recommends minimum absorbed doses of 70 Gy for Anastrepha spp., 101 Gy for Bactrocera jarvisi and B. tryoni, and 150 Gy for all Tephritidae except when fruits have been stored in hypoxic atmospheres.     

Irradiation of mangoes as a postharvest quarantine treatment for fruit flies (Diptera: Tephritidae)

Mangoes infested with third instar larvae were irradiated using Co-60 gamma rays and a dose interval of 2-250 Gy to assess the irradiation dose required to prevent adult emergence of the Mexican fruit fly (Anastrepha ludens), the West Indies fruit fly (A. obliqua), the sapote fruit fly (A. serpentina), and the Mediterranean fruit fly (Ceratitis capitata). Doses of 76.9, 87.3, 91.4 and 112.7 Gy, were estimated to inhibit 99.9968% (probit 9) of adult emergence forA. obliqua, A. serpentina, A. ludens, and C. capitata, respectively. Using mangoes infested with a total of 100,000 larvae of each species, the results obtained in the laboratory were confirmed using a dose of 100 Gy for the Anastrepha species and 150 Gy for C. capitata. No adult emergence was observed for any of the four species compared with approximately 80% emergence in the controls. A dose of 150 Gy is recommended as a generic quarantine treatment against potential infestation of these species in exported mangoes. A minor decrease in the ascorbic acid content was the only adverse effects observed in irradiated mangoes.     

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.     

Population structure,population history and DNA barcoding of fruit fly Bactrocera latifrons (Hendel) (Diptera: Tephritidae)

The fruit fly Bactrocera latifrons (Hendel) is an important pest of commercially significant plants such as chili, tomato and eggplant. The species is native to South and Southeast Asia, but has now invaded Japan, Hawaii and Africa. In this study, mitochondrial DNA sequences were used to infer genetic structure and demographic history of B. latifrons. The efficiency of DNA barcodes for identification of B. latifrons was also tested. Ninety‐three specimens infesting four host‐plant species were obtained from 11 sampling locations in Thailand. The mitochondrial haplotype network revealed no major divergent lineage, which was consistent with a phylogenetic analysis that found strong support for the monophyly of B. latifrons. Population pairwise F_ST revealed that most (65%) comparisons were not significantly different, suggesting a high rate of gene flow. Analysis of molecular variance (amova ) found no significant genetic differentiation among populations from different host‐plant species. Sharing of several haplotypes among flies from different host‐plants indicates that the flies were moved freely across the plant species. Demographic history analysis revealed that the population has undergone recent expansion dating back to the end of the last glaciation. Thus, the results indicate that both ongoing and historical factors have played important roles in determining the genetic structure and diversity of B. latifrons. DNA barcoding analysis revealed that B. latifrons specimens were clearly differentiated from other species with 100% correct identification. Therefore, cytochrome oxidase I (COI) barcoding sequences could be effectively used to identify this important pest species, which could encourage monitoring and control efforts for this species.     

应用种特异性PCR技术快速鉴定辣椒实蝇

【目的】辣椒实蝇 Bactrocera latifrons (Hendel)为我国重要的检疫性有害生物,其寄主范围广泛,危害严重。由于传统鉴定方法受到饲养周期、饲养条件、虫态等因素的限制,使得果蔬进出口贸易通关速度、疫情快速鉴定受到较大的影响,因此迫切需要开发关于实蝇的快速鉴定识别的技术。【方法】本研究基于mtDNA COI序列设计了一对能够准确鉴定辣椒实蝇的种特异性引物FL680和RL1057,选用辣椒实蝇作为阳性对照,选用番石榴实蝇B. correcta (Bezzi)、桔小实蝇 B. dorsalis (Hendel)和颜带实蝇 B. cilifer (Hendel)等20种实蝇作为阴性对照,进行PCR扩增并将PCR产物进行电泳检测。【结果】仅目标种辣椒实蝇能够扩增出清晰且单一的约378 bp的条带,其余实蝇种类均未出现条带。将本实验建立的种特异性PCR（SS-PCR）鉴定方法应用于实际检疫工作中并得到了验证,表明该方法具有强的种特异性。【结论】本文提出辣椒实蝇快速鉴定识别技术可应用于实蝇的疫情监测和口岸的检疫检测工作。     

Survival of Bactrocera latifrons (Diptera: Tephritidae) adults under constant and fluctuating low temperatures

Bactrocera latifrons (Hendel) is believed to have originated in Southeast Asia but has invaded Hawaii and most recently East Africa. This insect has also been recorded on Okinawa Island, the far south of Kyushu Island, Japan. To assess the overwintering ability of B. latifrons adults, survival at constant temperatures (8, 10, 12, 14, 15 °C) and under fluctuating thermal regimes (FTRs) was investigated. At 14 or 15 °C, more than 30 % of females survived for 90 days. Time required to kill 95 % of B. latifrons at 8 °C was estimated to be 13 days; at 10 °C, 29 days; and at 12 °C, 38 days for females, and 8, 17, and 24 days at the same above temperatures, respectively, for males, suggesting low cold tolerance of this species. The results show that females survive cold temperatures better than males. Under an FTR of 11 °C (22 h)/20 °C (2 h) (average 11.8 °C) survival of females drastically increased compared to that at a constant temperature of 12 °C, whereas the survival of males increased slightly. Survival under FTRs indicates that adult B. latifrons may not overwinter in the north of Tanegashima Island, located 30 km south of Kyushu Island, Japan.     

Sex-specific glands in tephritid fruit flies of the genera Anastrepha,Ceratitis, Dacus and Rhagoletis (Diptera : Tephritidae)

The objectives of this work were to systematically examine males and females of tephritid fruit flies from the genera Anastrepha, Ceratitis, Dacus and Rhagoletis for the presence of possible sex pheromone glands, and to determine whether particular glands may be characteristic of certain genera. Flies from the 4 genera were examined from paraffin embedded histological sections. Pleural epidermal glands and sexually dimorphic, enlarged salivary glands were found in males, but not in females, of 7 species of Anastrepha and in 2 species of Ceratitis. Females of these species do not develop the pleural epidermal glands at all, and although they have salivary glands, the glands do not have the large glandular mass of tissue that is found in males. The pleural glands were similar in all the males, and consisted of a single layer of enlarged, columnar epidermal cells in the pleural region of abdominal segments 3, 4 and 5. The salivary glands of males were divided into 4 types based upon structure.Pleural glands and enlarged salivary glands were searched for, but were not found, in 2 species of Rhagoletis and in 3 species of Dacus. Anal glands, opening externally on the last segment, were confirmed in C. capitata, and were found in C. rosa. Anal glands were not found in any of the other species. A diverticulum from the rectum, the rectal pouch or gland, was confirmed in D. dorsalis, D. cucurbitae and D. tryoni as already published, but this gland was not found in species of other genera. Growth of the pleural glands and salivary glands in males of A. ludens, A. fraterculus and C. capitata was described as a function of age of flies.     

Cold treatment for guava fruits infested with oriental fruit fly,Bactrocera dorsalis (Diptera: Tephritidae)

Guava (Psidium guajava Linnaeus) is an important horticulture crop in tropical and subtropical regions. However, guava transportation to the fruit market is regulated due to the risk of fruit fly infestations. The oriental fruit fly [Bactrocera dorsalis (Hendel), Tephritidae, Diptera], which damages numerous horticulture fruits, is the primary pest in guava. For fruit export, phytosanitary treatment is necessary to prevent the potential oriental fruit fly infestations through pest-infested fruits. In this study, cold treatment was administered to eliminate oriental fruit fly infestations in guava fruits. The optimal egg inoculation density was 200 eggs per fruit, and third instar larvae displayed the highest cold treatment tolerance. On assessing the efficacy of cold treatment, none of the third instar larvae in the fruits survived at a constant fruit core temperature of 0.5–1 °C for 11 days. A confirmatory test revealed that on maintaining a fruit core temperature of 0.5–1 °C for 12 days, 100% mortality was achieved among the fruit flies. In fruit quality assessment, guava fruits exposed to cold treatment still maintained their market value. Thus, cold treatment effectively disinfested guava fruits with possible fruit fly infestations, making it a viable quarantine treatment for guava fruits prior to their export.     

Potential increase in fruit fly (Diptera: Tephritidae) interceptions using ionizing irradiation phytosanitary treatments

Irradiation postharvest phytosanitary treatments are used increasingly and show further promise because of advantages compared with other treatments. Its chief disadvantage is that, unlike all other commercially used treatments, it does not provide acute mortality, although it prevents insects from completing development or reproducing. The objective of this research was to determine to what extent irradiated egg and early instars of tephritids would develop to later instars that could be found by phytosanitary inspectors or consumers. Mexican fruit fly, Anastrepha ludens (Loew), eggs and first instars in grapefruit, Citrus paradisi Macfayden, were irradiated with 70-250 Gy and held at approximately equal to 27 degrees C until third instars completed development. The accepted minimum absorbed phytosanitary dose for this pest is 70 Gy, although higher doses may be applied under commercial conditions. The more developed a fruit fly before it was irradiated, the greater the proportion that survived to the third instar. Also, dose was inversely related to developmental success, e.g., a mean of approximately 65 and 35%, respectively, of late first instars reached the third instar when irradiated with 70 and 250 Gy. Of those, 65.1 and 23.4%, respectively, pupariated, although no adults emerged. Irradiation may result in a greater frequency of live (albeit incapable of resulting in an infestation) larvae being found than would be expected compared with other treatments that provide acute mortality. The regulatory community should be aware of this and the fact that it does not increase the risk of irradiation phytosanitary treatments resulting in an infestation of quarantine pests.     

Vapor heat treatment for quarantine control of the oriental fruit fly (Diptera: Tephritidae) in papaya fruit from Thailand

A two-stage vapor heat treatment (VHT) is used commercially for disinfestation of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) in various tropical fruits exported from Thailand to international markets. In the present study, VHT was tested against B. dorsalis in papayas to confirm a high level of quarantine security. The first instar larva of B. dorsalis was the most heat tolerant life stage. The VHT consists of heating papaya fruits with hot air at 50–80 % RH from ambient temperature to a fruit center temperature of 43 °C (dry pre-heating period), then heating with saturated hot air to 47 °C (wet heating period) with a 20-min hold at 47°. In large-scale confirmatory tests of this VHT treatment schedule, none of the treated 78,405 first instar larvae survived. Papayas at the color break maturity stage treated by VHT and held under simulated commercial export conditions showed no differences in fruit quality compared with non-treated controls. VHT showed high efficacy in disinfestation of papayas of B. dorsalis while maintaining fruit quality and could be used as a standard quarantine treatment for papaya exported from Thailand.     

The response of two Bactrocera species (Diptera: Tephritidae) to fruit volatiles

Bactrocera dorsalis and B. correcta are serious pests of agricultural fruit crops. Both species are widely distributed in tropical and subtropical countries, especially in Asia. For integrated management of both Bactrocera species, understanding their olfactory behavior is vital for designing reliable control strategies. In this study, the response of female B. dorsalis and B. correcta adults to three main volatile components of fruits was evaluated using the Y-tube olfactometer. Our results showed that at higher concentrations all volatile components, except α-humulene and its combination with β-caryophyllene, attracted significantly more B. dorsalis than the untreated arm. For B. correcta, all the volatile components attracted significantly more females in the treated arm than the untreated arm. However, at 5% and 1% concentration, all the volatile components had similar attraction for B. dorsalis females. In the case of female B. correcta, the percentage of attraction was similar for all the individual volatile chemicals and their respective mixtures at 10% concentration. While, at 5% and 1% concentrations, the percentage of attraction was significantly higher for a mixture of β-caryophyllene and α-humulene than that of individual volatile components and all possible mixture of two and three volatile components. Based on the olfactometer results, this study concluded that 3-carene and the mixture of β-caryophyllene and α-humulene are strong attractants for female flies of B. dorsalis and B. correcta, respectively. This study might be helpful for the bait application against the female adults of B. dorsalis and B. correcta in farms and orchards.     

Revised irradiation doses to control melon fly, Mediterranean fruit fly, and oriental fruit fly (Diptera: Tephritidae) and a generic dose for tephritid fruit flies

Currently approved irradiation quarantine treatment doses for Bactrocera cucurbitae (Coquillet), melon fly; Ceratitis capitata (Wiedemann), Mediterranean fruit fly; and Bactrocera dorsalis (Hendel), oriental fruit fly, infesting fruits and vegetables for export from Hawaii to the continental United States are 210, 225, and 250 Gy, respectively. Irradiation studies were initiated to determine whether these doses could be reduced to lower treatment costs, minimize any adverse effects on quality, and support a proposed generic irradiation dose of 150 Gy for fruit flies. Dose-response tests were conducted with late third instars of wild and laboratory strains of the three fruit fly species, both in diet and in fruit. After x-ray irradiation treatment, data were taken on adult emergence, and adult female fecundity and fertility. Melon fly was the most tolerant of the three species to irradiation, and oriental fruit fly was more tolerant than Mediterranean fruit fly. Laboratory and wild strains of each species were equally tolerant of irradiation, and larvae were more tolerant when irradiated in fruit compared with artificial diet. An irradiation dose of 150 Gy applied to 93,666 melon fly late third instars in papayas resulted in no survival to the adult stage, indicating that this dose is sufficient to provide quarantine security. Irradiation doses of 100 and 125 Gy applied to 31,920 Mediterranean fruit fly and 55,743 oriental fruit fly late third instars, respectively, also resulted in no survival to the adult stage. Results support a proposed generic irradiation quarantine treatment dose of 150 Gy for all tephritid fruit flies.     

Microsatellite markers for the pest fruit fly,Bactrocera papayae (Diptera: Tephritidae) and other Bactrocera species

The dorsalis complex contains some of the most economically important fruit fly pests of the Asia–Pacific regions, including Bactrocera dorsalis, Bactrocera papayae and Bactrocera carambolae. These species are morphologically indistinct and genetically very similar. We describe the development of 12 microsatellite markers isolated from a representative of the dorsalis complex, B. papayae. We show the potential utility of the B. papayae microsatellites and a set of microsatellites isolated from Bactrocera tryoni as population and species markers for the dorsalis complex.     

Efficacy of wax matrix bait stations for Mediterranean fruit flies (Diptera: Tephritidae)

Tests were conducted that evaluated efficacy of wax matrix bait stations for Ceratitis capitata (Wiedemann) adults in Guatemala. Bait stations were exposed to outdoor conditions to determine effect of weathering on longevity as indicated by bait station age. Results of laboratory tests found that bait stations with spinosad and ammonium acetate remained effective for at least 31 d compared with pesticide-free controls, although there was some loss of efficacy over time. Percentage mortality for bait station strips with 2% spinosad and 1% ammonium acetate decreased from 100 +/- 0.0% on day 0 to 70 +/- 7.1% after 31 d. Ammonia concentration had little effect on percentage mortality although there was some indication that ammonia concentration affected number of flies observed on the bait stations. Bait station strips (one per cage) were more effective than controls for 6-8 wk when tests were conducted in field cages (3 m diameter x 2 m), but only 2-3 wk when tests were conducted in large (2.5 m high and 6.0 m wide and 7.5 m long) field cages. Longevity was restored when multiple bait stations (3, 6, or 12) were deployed per cage. Bait stations containing methomyl were used for field tests of efficacy for wild flies. Dipped lure bait stations, which were made by coating two edges of commercial ammonium acetate and trimethylamine lures, killed six times more flies than corn cob bait stations dipped into a Nulure/malathion solution. They also killed more flies than pesticide-free controls for 8 wk.     

Capture of Bactrocera fruit flies (Diptera: Tephritidae) in traps baited with liquid versus solid formulations of male lures

Bactrocera dorsalis (Hendel) and B. cucurbitae (Coquillett) (Diptera: Tephritidae) are important agricultural pests of the Pacific region. Detection and control of these species rely largely on traps baited with male-specific attractants (parapheromones), namely methyl eugenol for B. dorsalis and cue lure for B. cucurbitae. Presently, these lures (plus naled, an insecticide) are applied in liquid form, although this procedure is time-consuming, and naled as well as methyl eugenol may pose human health risks. Recently, a solid formulation (termed a wafer) has been developed that contains both male lures (plus DDVP, an insecticide), and here we present data from field tests in California and Hawaii that compare the effectiveness of liquid versus solid formulations of the lures in capturing marked, released males of these two Bactrocera species. For both species and in both California and Hawaii, traps baited with the solid formulation of the male lure captured similar or significantly more released flies than the liquid formulation for both fresh and aged baits. Traps in Hawaii also captured wild (unmarked) males of both B. dorsalis and B. cucurbitae, and the results obtained for wild flies were similar to those recorded for released flies for both species. Collectively, the results presented suggest that the solid dispenser of the male lures constitutes a reliable substitute for the liquid formulation in detecting incipient Bactrocera outbreaks.     

桔小实蝇、木瓜实蝇和番石榴实蝇耐热性的热动力学分析

果实蝇属是重要的检疫性有害生物之一, 其中桔小实蝇Bactrocera dorsalis (Hendel)、 木瓜实蝇B. papayae Drew & Hancock和番石榴实蝇B. correcta (Bezzi)近几年在口岸检出率居高。本研究利用热水浸泡处理法比较这3种实蝇的卵、 1龄幼虫和3龄幼虫在44~47℃下的耐热性, 利用热动力学模型和活化能比较每种实蝇的耐热虫态以确定耐热种。结果表明： 在测定温度范围内, 3种实蝇卵、 1龄幼虫和3龄幼虫的死亡率都与处理时间呈正相关。热动力学系数取0.5时, 最适合热动力学模型预测3种实蝇在各实验温度LT_99.9968的致死时间。3种实蝇在44~47℃耐热性均为： 卵>1龄幼虫>3龄幼虫。番石榴实蝇在3种实蝇中最耐热。本研究结果为实蝇热处理指标的制定提供了实验依据。     

Detection of the solanum fruit fly, Bactrocera latifrons (Hendel) in Tanzania (Dipt., Tephritidae)

Abstract:  The presence of the Solanum fruit fly, Bactrocera latifrons , in Africa is reported for the first time, based on trapped and reared specimens in Tanzania. Two new host records, Solanum aethiopicum and Solanum macrocarpon , are reported.