Host use of Bactrocera latifrons, a new invasive tephritid species in Tanzania

The Impact of Fast Radiation on the Phylogeny of Bactrocera Fruit Flies as Revealed by Multiple Evolutionary Models and Mutation Rate-Calibrated Clock

Several true fruit flies (Tephritidae) cause major damage to agriculture worldwide. Among them, species of the genus Bactrocera are extensively studied to understand the traits associated with their invasiveness and ecology. Comparative approaches based on a reliable phylogenetic framework are particularly effective, but several nodes of the Bactrocera phylogeny are still controversial, especially concerning the reciprocal affinities of the two major pests B. dorsalis and B. tryoni. Here, we analyzed a newly assembled genomic-scaled dataset using different models of evolution to infer a phylogenomic backbone of ten representative Bactrocera species and two outgroups. We further provide the first genome-scaled inference of their divergence by calibrating the clock using fossil records and the spontaneous mutation rate. The results reveal a closer relationship of B. dorsalis with B. latifrons than to B. tryoni, contrary to what was previously supported by mitochondrial-based phylogenies. By employing coalescent-aware and heterogeneous evolutionary models, we show that this incongruence likely derives from a hitherto undetected systematic error, exacerbated by incomplete lineage sorting and possibly hybridization. This agrees with our clock analysis, which supports a rapid and recent radiation of the clade to which B. dorsalis, B. latifrons and B. tryoni belong. These results provide a new picture of Bactrocera phylogeny that can serve as the basis for future comparative analyses.

Host Preference of Bactrocera latifrons (Hendel) (Diptera: Tephritidae) Among Fruits of Solanaceous Plants

Simple Summary

Bactrocera latifrons (Diptera: Tephritidae) is the major pest in economic chili and eggplant of Thailand. Although B. latifrons has many host plant species, it does not unequally prefer each host plant. Results of this study indicated that among seven host plant species of family Solanaceae, Capsicum fruits were preferred by B. latifrons for oviposition over Solanum fruits. Bird chili and banana pepper were the most preferred hosts for B. latifrons. Turkey berry was least preferred by B. latifrons. Results of this study develop knowledge of the specific mechanisms by which host fruit varieties, host fruit species and physiological changes during ripening of host fruit influence B. latifrons’ preference. This is of potential value in field management, quarantine and plant breeding using traditional or transgenic approaches.

Abstract

Host preference of Bactrocera latifrons (Hendel) (Diptera: Tephritidae), major chili and nightshade pest, was studied using seven host plant species of family Solanaceae. Two nightshade species, eggplant, Solanum melongena L. and turkey berry, Solanum torvum Sw.; three pepper and one large chili cultivar of Capsicum annum L., banana pepper, cayenne pepper, noom pepper and duey kai chili; and one small chili cultivar of Capsicum frutescens L., bird chili, were used as tested host plants of B. latifrons for a series of choice test and no-choice test under the laboratory. Results revealed that B. latifrons preferred Capsicum fruits for oviposition rather than Solanum fruits. Bird chili and banana pepper were the most preferred host for B. latifrons, with the highest number of pupae per gram of fruit in no-choice and choice experiment, respectively. Although the best larval performance parameters of B. latifrons were better for eggplant than for other Solanaceous plants, fruit characteristics and total phenolic content in fruit play a major role for host preference of B. latifrons. Turkey berry was least preferred by B. latifrons, with the lowest number of pupae per fruit and it was not oviposited by B. latifrons female fly under the choice situation at all stages of ripeness.

Revised Distribution of Bactrocera tryoni in Eastern Australia and Effect on Possible Incursions of Mediterranean Fruit Fly: Development of Australia's Eastern Trading Block

Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), commonly called 'Queensland fruit fly' in Australia, and Mediterranean fruit fly (Ceratitis capitata Wiedemann) (Diptera: Tephritidae) are the two most economically important fruit fly in Australia with B. tryoni in the east and Mediterranean fruit fly in the west. The two species coexisted for several decades, but it is believed that B. tryoni displaced Mediterranean fruit fly. In southeastern Australia, this was deemed inadequate for export market access, and a large fruit fly free zone (fruit fly exclusion zone) was developed in 1996 where B. tryoni was eradicated by each state department in their portion of the zone. This zone caused an artificial restricted distribution of B. tryoni. When the fruit fly exclusion zone was withdrawn in Victoria and New South Wales in 2013, B. tryoni became endemic once again in this area and the national distribution of B. tryoni changed. For export markets, B. tryoni is now deemed endemic to all eastern Australian states, except for the Greater Sunraysia Pest-Free Area. All regulatory controls have been removed between eastern states, except for some small zones, subject to domestic market access requirements. The eastern Australian states now form a B. tryoni endemic trading group or block. All Australian states and territories maintain legislation to regulate the movement of potentially infested host fruit into their states. In particular, eastern states remain active and regulate the entry of commodities possibly infested with Mediterranean fruit fly. The combination of regulatory controls limits the chances of Mediterranean fruit fly entering eastern states, and if it did, Mediterranean fruit fly is unlikely to establish in the opposition to a well-established B. tryoni population.

Niche partitioning among two Ceratitis rosa morphotypes and other Ceratitis pest species (Diptera, Tephritidae) along an altitudinal transect in Central Tanzania

Two standard parapheromones, trimedlure (routinely used for monitoring Ceratitis rosa and Ceratitis capitata) and terpinyl acetate (routinely used for monitoring Ceratitis cosyra) were compared with enriched ginger root oil (EGO) lure for detecting and monitoring the presence and relative population abundance of these particular pest species. Standard yellow fruit fly traps were used for the comparison, which was conducted at 10 sites along an altitudinal transect ranging from 540 to 1650 masl on the Uluguru mountains, in Morogoro Region (Central Tanzania). A gradual change of relative occurrence of the two Ceratitis rosa morphotypes was clear from the EGO lure trapping. The morphotype R1 was predominant at lower altitudes while morphotype R2 was predominant at higher altitudes. Further experiments are needed to confirm the consistency of the observed pattern across regions, seasons and years as well as possible differences in the developmental physiology of both morphotypes. The mango fruit fly, Ceratitis cosyra, showed a distinct predominance at altitudes below 800 masl as shown in both the EGO lure and the terpinyl acetate trapping. The catches of all three target species were higher in traps with the EGO lure compared to the conventional lures trimedlure and terpinyl acetate. It is argued that for these species EGO lure can act as a suitable and more effective alternative for trimedlure and terpinyl acetate parapheromones. In addition, EGO lure has the added advantage that it combines the taxon spectrum for the two latter substances, thus requiring the use of only a single attractant.

Assessment of Navel Oranges, Clementine Tangerines, and Rutaceous Fruits as Hosts of Bactrocera cucurbitae and Bactrocera latifrons (Diptera: Tephritidae)

Export of Citrus spp. fruits may require risk mitigation measures if grown in areas with established tephritid fruit fly (Diptera: Tephritidae) populations capable of infesting the fruits. The host status of Citrus spp. fruits is unclear for two tephritid fruit fly species whose geographic ranges have expanded in recent years: melon fly, Bactrocera cucurbitae (Cocquillett), and Bactrocera latifrons (Hendel). In no choice cage infestation studies, B. latifrons oviposited into intact and punctured Washington navel oranges (Citrus sinensis [L.] Osbeck) and Clementine tangerines (C. reticulata L. var. Clementine), but eggs rarely developed to the adult stage. B. cucurbitae readily infested intact and punctured tangerines, and to a lesser extent punctured oranges, but did not infest intact oranges. Limited cage infestation and only a single literature report of field Citrus spp. infestation suggest that risk mitigation of Citrus spp. for B. latifrons is not needed. Risk mitigation options of Citrus spp. for B. cucurbitae, including heat and cold treatments and systems approaches, are discussed.