Identification and biochemical characterisation of α-amylase in the alimentary tract of Mediterranean fruit fly,Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Mediterranean fruit fly (Medfly), Ceratitis capitata, is an important pest of many fruit crops in temperate and subtropical regions worldwide. α-Amylases are hydrolytic enzymes involved in carbohydrate metabolism in insects. There is no report about α-amylase activity in C. capitata in literature. So, the aim of the current study was biochemical characterisation of α-amylase in the alimentary canal of the pest to gain a better understanding of digestive physiology of the insect. α-Amylase of Medfly was extracted and characterised using starch as the substrate. The results showed the presence of α-amylase activity in the gut of the insect for carbohydrate digestion. Optimum activity of the enzyme occurs at pH 8.0 and 40?°C. The most effective activator of the enzyme was determined in treatment with 20?mM CaCl₂. Na⁺, K⁺ and Mg²⁺ ions also activated the enzyme. Native PAGE of α-amylase showed two isoenzymes suggesting the importance of α-amylase in the carbohydrate digestion in the insect. Understanding of the digestive physiology and α-amylase activity of Medfly is important when new management strategies for this economically important pest are devised.     

Insectary production and synopsis of Fopius caudatus (Hymenoptera: Braconidae), parasitoid of tephritid fruit flies indigenous to Africa

Fopius caudatus (Szépligeti) is an endophagous koinobiont egg-larval parasitoid native to Africa. It has recently been noted as a candidate for augmentative biological control of several Dacinae fruit fly pests (Diptera: Tephritidae), due to its ability to parasitize the egg stage. Previous attempts to establish this parasitoid in Hawaii, Guatemala, and Costa Rica were unsuccessful due to inability to maintain parasitoid colonies under laboratory conditions. A cohort of F. caudatus collected from Kenyan fruit flies infesting Coffea arabica was successfully colonized in Hawaii at 28 °C and 60–80% RH, resulting in the development of a laboratory-adapted colony amenable for mass production. The parasitoid was successfully developed from eggs of Ceratitis capitata and Bactrocera latifrons as a factitious host. The wasps were propagated for 15 weeks until the rearing stabilized, at which point >10,500 adults were produced with an overall sex ratio of 0.52 females and a mean host parasitism rate of 17.3%. It could parasitize Medfly eggs in fruits other than coffee, including papaya, mango, pear, squash, and sweet pepper. Female F. caudatus oviposited mainly in 24–48 h old Medfly eggs, although occasionally a few individuals eclosed when first instar fly larvae were exposed. Mean developmental time from egg to adult was 19.8 d for males and 21.5 d for females. Mean longevity was 5.2 d for males and 14.2 d for host-deprived females. This study enabled us to maintain a colony of F. caudatus for research and redistribution to other countries for biocontrol programs against Medfly.     

The isolation of microsatellite loci in the Mediterranean fruitfly Ceratitis capitata (Diptera: Tephritidae) using a biotin/streptavidin enrichment technique

The Medfly (Ceratitis capitata) is a polyphagous dipteran pest which has spread from North Africa to the countries of the Mediterranean Basin and has also invaded tropical and subtropical regions throughout the world. Colonizing populations typically possess low levels of genetic variability. Microsatellites provide an effective means of investigating the population structure of such genetically depauperate populations, however, microsatellite markers traditionally require a long phase of development in new taxa. We used a biotin/streptavidin capture technique to isolate microsatellites directly from C. capitata genomic DNA and we describe here the identification of seven polymorphic microsatellite markers in C. capitata.     

Systematic revision of the subgenus Ceratitis MacLeay s.s. (Diptera, Tephritidae)

The fruit fly genus Ceratitis MacLeay (Diptera, Tephritidae) comprises several important pest species attacking a wide range of unrelated fruits. This is the third paper in a series revising the genus, and deals with representatives of the subgenus Ceratitis s.s . Eight species are recognized: Ceratitis brachychaeta Freidberg, C. caetrata Munro, C. capitata (Wiedemann), C. catoirii Guerin-Meneville, C. comuta (Bezzi), C. malgassa Munro, C. manjakatompo Hancock and C. pinax Munro. Lectotypes are designated for C. catoirii and C. pinax . A key for both sexes is provided, with illustrations of cephalic bristles, mesonotal and wing patterns, and shape of aculeus. All species are Afrotropical, except for 67. capitata , which has become widespread. The phylogeny and biogeography of Ceratitis s.s . are discussed, based on a cladistic analysis, and showing indications that the mediterranean fruit fly, C. capitata , may have its origins in eastern Africa. The relationship of this subgenus within the genus Ceratitis s.l . is also outlined.     

Conditional embryonic lethality to improve the sterile insect technique in Ceratitis capitata (Diptera: Tephritidae)

Background  

The sterile insect technique (SIT) is an environment-friendly method used in area-wide pest management of the Mediterranean fruit fly Ceratitis capitata (Wiedemann; Diptera: Tephritidae). Ionizing radiation used to generate reproductive sterility in the mass-reared populations before release leads to reduction of competitiveness.     

Advancements in management of major fruit flies (Diptera: Tephritidae) in North Africa and future challenges: A review

Fruit flies are one of the most economically damaging pests of fleshy fruits worldwide. Two species of highest concern for fruit production in North Africa are the Mediterranean fruit fly (Medfly) Ceratitis capitata (Wied.) and the peach fruit fly (PFF) Bactrocera zonata (Saunders) (in Egypt and Libya only). Currently, both fruit fly species are mainly targeted by chemical applications of broad-spectrum contact insecticides. Despite the disparities in control efforts among North African countries, government and research are focused on reducing chemical reliance and adopt more environmentally friendly technologies. In this review, advances in integrated pest management (IPM) implementation against fruit flies are outlined for each country. In addition, challenges for future efforts are identified with emphasis on the efficacy of trapping for monitoring and control.     

Issues Concerning the Eradication or Establishment and Biological Control of the Mediterranean Fruit Fly,Ceratitis capitata(Wiedemann) (Diptera: Tephritidae), in California

Classical biological control is suggested as a tool worth developing now for possible future use in the integrated pest management of the Mediterranean fruit fly (Medfly),Ceratitis capitata(Wiedemann), in California. Three factors that impact broadly on developing and implementing such a biological control program are: (1) the question of Medfly establishment, (2) quarantine considerations, and (3) agricultural and urban concerns. Each of these factors and their combined effects must be considered when discussing biological control of Medfly in California as shaped by historical perspectives on Medfly invasions, methods of Medfly eradication, and past biological control efforts against Medfly. We believe that biological control research should play a foundational role in any future Medfly management programs in California. Development of biological control should involve life history studies of Medfly and its natural enemies in their area of endemicity in sub-Saharan, southeast Africa. Medfly has been studied and should continue to be studied in areas it has invaded, because information derived from such studies provides insights into the potential distribution, abundance, and impact of Medfly populations in California. A plan for a biological research program on Medfly and its relatives and a biological control strategy are presented.     

Determination of host status of citrus fruits against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Abstract  The Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann) is a pest of citrus in parts of Western Australia. Three citrus cultivars: Valencia oranges, Eureka lemons and Imperial mandarins, as well as non-citrus control fruits, were examined for attractiveness and suitability to Medfly in the field and in the laboratory using choice and no-choice experiments. Oranges were more susceptible to Medfly than mandarins and lemons. Punctures in the skin had a significant impact on the degree of infestation in both citrus and non-citrus control fruit. Artificial infestation and larval survivorship were used to investigate the suitability of each cultivar to Medfly under laboratory conditions. Oranges and mandarins were suitable for the development of Medfly, but lemons were a poor host. When each cultivar was in season, field cage trials demonstrated that infestation occurred in oranges and mandarins but not in lemons.     

Acceptance and suitability of different host stages of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and seven other tephritid fruit fly species to Tetrastichus giffardii Silvestri (Hymenoptera: Eulophidae)

Tetrastichus giffardii Silvestri is a gregarious eulophid endoparasitoid of several tephritid fruit fly species. Host stage suitability was studied using nine age groups of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), namely, eggs less than 24 h and between 24 and 48 h old, and 1- to 7-day-old larvae. Life table studies for T. giffardii using C. capitata as host were done at 26 ± 5 °C and 55–60% RH. Egg load in relation to age of the female parasitoid was also assessed as was the effect of host deprivation on adult longevity. Host acceptance and suitability were examined with respect to eight species of tephritids. Potential hosts so tested were five Ceratitis species, the Medfly, C. capitata, the mango fruit fly, Ceratitis cosyra (Walker), the Natal fruit fly, Ceratitis rosa Karsch, Ceratitis fasciventris (Bezzi), and Ceratitis anonae Graham; two Bactrocera species, the melon fruit fly, Bactrocera cucurbitae (Coquillett) and the newly invasive Bactrocera invadens Drew, Tsuruta, and White; and one Dacus species, the lesser pumpkin fly, Dacus ciliatus Loew. No parasitoids were obtained from eggs while all larval stages were suitable though at varying degrees. Parasitism and number of progeny was related to host age in a curvilinear manner with maxima at 4- to 5-day-old larvae. By contrast, development time decreased with age of host larvae while sex ratio was not affected. The intrinsic rate of increase was 0.17 ± 0.01; gross and net reproductive rates were 64.9 ± 4.3 and 44.9 ± 3.8, respectively. Non-ovipositing females lived significantly longer than ovipositing ones. The females accepted all host species tested, but only C. capitata, D. ciliatus and, to a much lesser extent, C. cosyra were suitable. In the remaining host species, most eggs were encapsulated. In C. capitata and D. ciliatus, percent parasitism was similar, but number of progeny was lower and the sex ratio, as the proportion of females, was higher when the parasitoid was reared on D. ciliatus. Progeny per puparium were also similar for the two hosts. In the light of these results it can be concluded that T. giffardii has a narrow host range, but it attacks and successfully develops in larvae representing a wide range of ages.     

Susceptibility of selected apple cultivars to the Mediterranean fruit fly

Ceratitis capitata (Wiedemann), the Mediterranean fruit fly, is one of the key pest species affecting deciduous fruit orchards along the Mediterranean coasts. Because of global warming, C. capitata is gradually spreading north and is becoming a major pest of apples. Determining the susceptibility of the main apple varieties grown in the region will serve as a cornerstone to the management of this pest. In this study, we show the results of a field and laboratory no‐choice test conducted to determine the Medfly preferences on different apple cultivars. The seven main varieties of apples (Gala, Red Delicious, Golden Delicious, Granny Smith, Kanzi, Morgen Dallago and Fuji) were tested. The results demonstrate that C. capitata lays eggs on all apple cultivars in both field and laboratory conditions. The Granny Smith, Red Delicious and Morgen Dallago varieties showed the lowest susceptibility in laboratory conditions, (0.75, 1.55, 2 oviposition punctures/fruit, respectively), with significant differences in oviposition compared to the Golden Delicious, Kanzi and Fuji (3.27, 3.31, 3.1 oviposition punctures/fruit, respectively) varieties, which were shown to be the most susceptible to Medfly attack in laboratory conditions. On the other hand, only slight and not statistically significant differences emerged from the field trials. In relation to the physico‐chemical characteristics, the apple cultivars showing the lowest susceptibility (Granny Smith, Red Delicious and Morgen Dallago) had harder peels and pulps and lower sugar contents than the most susceptible cultivars (Golden Delicious, Fuji and Kanzi). These results were also confirmed through evaluation of larval development on different varieties. In fact, Granny Smith, Red Delicious and Morgen Dallago were the three varieties that did not allow adequate larval and adult development and reduced the possibility of the emergence of a new generation.     

Influence of ground beetles (Carabidae) as biological agent to control of the Mediterranean fruit fly pupae,Ceratitis capitata,in Iranian citrus orchards

Damage by Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in the northern Iranian citrus orchards has been led to spray by different chemical pesticides. The present study was conducted in the citrus orchard in Mazandaran province of Iran where with the exception of mineral oil treatments for scale insects, had not been sprayed with synthetic insecticides for six years. The purpose of this study was initially to investigate faun and seasonal activity of predaceous ground carabid beetles in the citrus orchards. Additionally, their role as predators of Ceratitis capitata (Wiedemann) pupae was evaluated under laboratory and field conditions. Predation in laboratory was evaluated by no choice feeding experiments while predation under field conditions was evaluated by molecular detection of the pest DNA in the gut contents of field-collected Carabids. A total of 3437 beetles of ten carabid species were collected from a non-chemical treatment citrus orchard. The results of the seasonal density fluctuation indicated increasing population in spring reaching the highest in September, simultaneously with the peak of fruit fly damage, and thereafter decreasing during winter when the pest was overwintering. However, three species, Harpalus rufipes, Broscus karelinii and Brachinus brevicollis were most abundant in the field collection but the results of no-choice experiments in the laboratory indicated H. rufipes, B. karelinii and Pterostichus macer were the most voracious predators on pupae. Results of gut content analysis of the voracious species indicated the positive testing for pest DNA in 79.16 % of H. rufipes, 76.92 % of B. karelinii and 75 % of P. macer of analyzed beetles. The results of the study strongly indicated that in citrus orchards where intensive spraying is eliminated, natural enemies such as Carabid beetles could play an important role in reducing pests such as medfly.     

Pathogenicity of Beauveria bassiana isolated from Moroccan Argan forests soil against larvae of Ceratitis capitata (Diptera: Tephritidae) in laboratory conditions

The Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), is the major tephritid pest in Morocco. This pest survives in Moroccan forests Argania spinosa and continually invades the nearest agricultural areas. Entomopathogenic fungi are an interesting tool for fruit fly control and hold a useful alternative to conventional insecticides. However, primary selection of effective pathogens should be taken in laboratory condition prior to applying them in the field. Here, we used third late instar larvae of C. capitata to investigate the effectiveness of 15 local Beauveria bassiana isolates. Results showed that all isolates were able to infect the larval stage, producing a large mortality rate in puparia ranging from 65 to 95 % and caused significant reduction in adult emergence. The fungal treatments revealed that the mycosis occurred also in adults escaping infection as pupariating larvae. The percentage of mycosed puparia was highest in strain TAM6.2 (95 %) followed by ERS4.16 (90 %), therefore they were the most virulent. Median lethal concentration (LC₅₀) was studied for five isolates at four concentrations ranging from 10⁵ to 10⁸ conidia ml^?1. The results showed that the slopes of regression lines for B. bassiana ERS4.16 (slope = 0.386) and TAM6.2 (slope = 0.41) were the most important and had the lowest LC₅₀ values (2.85 × 10³ and 3.16 × 10³ conidia ml^?1 respectively). This investigation suggests that the soil of Argan forests contains pathogenic B. bassiana isolates and highlights for the first time their potential as biological control toward C. capitata larval stage in Morocco.     

Host species and vegetable fruit suitability and preference by the parasitoid wasp Fopius arisanus

Parasitoids that oviposit in a concealed host inside a plant part need to be able to find both the plant and the host. Egg parasitoids of fruit‐infesting Tephritidae need to assess the oviposition site based both on the host egg and the infested fruit. Infestation by Tephritidae fruit flies threatens fruit and vegetable production. Management methods have been implemented including biological control, using Fopius arisanus Sonan (Hymenoptera: Braconidae). The parasitism by F. arisanus in three Tephritidae flies in vegetable fruits was investigated. Laboratory assays were conducted to assess the parasitoid's preference and survival. Zucchini, sweet pepper, and tomato were artificially infested with eggs of Bactrocera dorsalis Hendel, Ceratitis capitata Wiedemann, and Ceratitis cosyra Walker (all Diptera: Tephritidae), then exposed to mated naïve F. arisanus females in a 20:1 egg:parasitoid ratio. Parasitoid behavioral activities (resting, antennating, probing, ovipositing) were observed on the infested fruits. Parasitism rate was determined by dissection of fruit fly eggs under a stereomicroscope. Behavioral activities of F. arisanus differed between all the fruits when infested with B. dorsalis or C. cosyra eggs but differed only between some of the fruits when infested with C. capitata. Fopius arisanus preferred B. dorsalis over C. capitata and C. cosyra, with a parasitism rate 2× higher on B. dorsalis compared to the Ceratitis species. Preference for fruits was dependent on the infesting fruit fly. The emergence of F. arisanus was higher with B. dorsalis than with Ceratitis spp. Although B. dorsalis completed its development earlier than Ceratitis spp., host fly species did not affect the developmental time of F. arisanus. We discuss the significance of F. arisanus preference in relation to naturally occurring Tephritidae infestations. We also discuss whether some fruits might constitute a refuge for Tephritidae flies and whether this will affect the current biological control efforts against B. dorsalis.     

Exploitation of the Medfly Gut Microbiota for the Enhancement of Sterile Insect Technique: Use of Enterobacter sp. in Larval Diet-Based Probiotic Applications

The Mediterranean fruit fly (medfly), Ceratitis capitata, is a pest of worldwide substantial economic importance, as well as a Tephritidae model for sterile insect technique (SIT) applications. The latter is partially due to the development and utilization of genetic sexing strains (GSS) for this species, such as the Vienna 8 strain, which is currently used in mass rearing facilities worldwide. Improving the performance of such a strain both in mass rearing facilities and in the field could significantly enhance the efficacy of SIT and reduce operational costs. Recent studies have suggested that the manipulation of gut symbionts can have a significant positive effect on the overall fitness of insect strains. We used culture-based approaches to isolate and characterize gut-associated bacterial species of the Vienna 8 strain under mass rearing conditions. We also exploited one of the isolated bacterial species, Enterobacter sp., as dietary supplement (probiotic) to the larval diet, and we assessed its effects on fitness parameters under the standard operating procedures used in SIT operational programs. Probiotic application of Enterobacter sp. resulted in improvement of both pupal and adult productivity, as well as reduced rearing duration, particularly for males, without affecting pupal weight, sex ratio, male mating competitiveness, flight ability and longevity under starvation.     

Host specificity of the egg pupal parasitoid Fopius arisanus (Hymenoptera: Braconidae) in La Reunion

Fopius arisanus is a polyphagous parasitoid of Tephritidae, which has been recently introduced to La Réunion Island as part of a classical biological control programme. We carried out laboratory experiments to assess the host specificity of this parasitoid, initially reared on Bactrocera zonata, and then offered for parasitization the eight local tephritid pest species. Naive or experienced parasitoid females were given tephritid eggs in no choice tests. Fopius arisanus females parasitize all fly species but parasitism varies with host species. No adult wasps emerge from Bactrocera cucurbitae and the survival of this species is only slightly affected by parasitism. Dissections show that the late instars of this fly may eliminate the parasitoid by encapsulation. When developing on Ceratitis capitata, Ceratitis rosa, Dacus ciliatus, Dacus demmerezi, and Neoceratitis cyanescens, parasitoid survival rate ranges from 10 to 25%. Bactrocera zonata and Ceratitis catoirii are the best hosts, yielding parasitoid survival rates of more than 70% with no premature mortality. The egg-larval mortality of C. capitata, C. rosa, D. ciliatus, and N. cyanescens, and the pupal mortality of D. demmerezi, are significantly increased by parasitism. The size of emerging adults is affected by host species and is correlated to pupal weight. Bactrocera zonata would be a favorable host to support routine colonization of F. arisanus for mass production of this parasitoid.     

The ground beetle Pseudophonus rufipes revealed as predator of Ceratitis capitata in citrus orchards

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) is a major citrus pest in Spain. Although medfly is being controlled chemically, alternative biorational strategies should be developed, like those based on conservation biological control of polyphagous predators. The ground beetle Pseudophonus rufipes (De Geer) is the most abundant carabid inhabiting the ground of citrus orchards in eastern Spain. However, little is known about its activity–density and predatory role against C. capitata in the citrus agroecosystem. Here, we report on its predatory potential on the medfly’s developmental stages that take place in the citrus ground. This carabid species preyed efficiently on C. capitata third instar larvae and especially on pupae but not on teneral adults. Moreover, predation under field conditions was evaluated by detecting C. capitata DNA remains using PCR-based gut-content analysis. Half-life DNA detectability of C. capitata was of 32.33 h. Pseudophonus rufipes specimens were field-collected after C. capitata sterilized pupae were deployed in a commercial citrus orchard. Thereafter, the carabids captured by pitfall traps were analyzed, being DNA-remains of C. capitata detected in 22.2% of them. Data reported here clearly suggest that P. rufipes could play an important role in regulating medfly populations in citrus orchards. This information is particularly useful when biological control conservation strategies are being considered to control this pest.     

Ecological niches and potential geographical distributions of Mediterranean fruit fly (Ceratitis capitata) and Natal fruit fly (Ceratitis rosa)

Aim To predict and compare potential geographical distributions of the Mediterranean fruit fly (Ceratitis capitata) and Natal fruit fly (Ceratitis rosa). Location Africa, southern Europe, and worldwide. Methods Two correlative ecological niche modelling techniques, genetic algorithm for rule‐set prediction (GARP) and a technique based on principal components analysis (PCA), were used to predict distributions of the two fly species using distribution records and a set of environmental predictor variables. Results The two species appear to have broadly similar potential ranges in Africa and southern Europe, with much of sub‐Saharan Africa and Madagascar predicted as highly suitable. The drier regions of Africa (central and western regions of southern Africa and Sahelian zone) were identified as being less suitable for C. rosa than for C. capitata. Overall, the proportion of the region predicted to be highly suitable is larger for C. capitata than for C. rosa under both techniques, suggesting that C. capitata may be tolerant of a wider range of climatic conditions than C. rosa. Worldwide, tropical and subtropical regions are highlighted as highly suitable for both species. Differences in overlap of predictions from the two models for these species were observed. An evaluation using independent records from the adventive range for C. capitata and comparison with other predictions suggest that GARP models offer more accurate predictions than PCA models. Main conclusions This study suggests that these species have broadly similar potential distributions worldwide (based on climate), although the potential distribution appears to be broader for C. capitata than for C. rosa. Ceratitis capitata has become invasive throughout the world, whereas C. rosa has not, despite both species having broadly similar potential distributions. Further research into the biology of these species and their ability to overcome barriers is necessary to explain this difference, and to better understand invasion risk.