Rick Kurashima

Big Genomes Facilitate the Comparative Identification of Regulatory Elements

The identification of regulatory sequences in animal genomes remains a significant challenge. Comparative genomic methods that use patterns of evolutionary conservation to identify non-coding sequences with regulatory function have yielded many new vertebrate enhancers. However, these methods have not contributed significantly to the identification of regulatory sequences in sequenced invertebrate taxa. We demonstrate here that this differential success, which is often attributed to fundamental differences in the nature of vertebrate and invertebrate regulatory sequences, is instead primarily a product of the relatively small size of sequenced invertebrate genomes. We sequenced and compared loci involved in early embryonic patterning from four species of true fruit flies (family Tephritidae) that have genomes four to six times larger than those of Drosophila melanogaster. Unlike in Drosophila, where virtually all non-coding DNA is highly conserved, blocks of conserved non-coding sequence in tephritids are flanked by large stretches of poorly conserved sequence, similar to what is observed in vertebrate genomes. We tested the activities of nine conserved non-coding sequences flanking the even-skipped gene of the teprhitid Ceratis capitata in transgenic D. melanogaster embryos, six of which drove patterns that recapitulate those of known D. melanogaster enhancers. In contrast, none of the three non-conserved tephritid non-coding sequences that we tested drove expression in D. melanogaster embryos. Based on the landscape of non-coding conservation in tephritids, and our initial success in using conservation in tephritids to identify D. melanogaster regulatory sequences, we suggest that comparison of tephritid genomes may provide a systematic means to annotate the non-coding portion of the D. melanogaster genome. We also propose that large genomes be given more consideration in the selection of species for comparative genomics projects, to provide increased power to detect functional non-coding DNAs and to provide a less biased view of the evolution and function of animal genomes.

Behavioural switch of female Mediterranean fruit fly, Ceratitis capitata: mating and oviposition activity in outdoor field cages in Hawaii

1 Laboratory‐reared normal, and wild female Mediterranean fruit flies, Ceratitis capitata (Wiedemann), were assayed in outdoor field cages to assess the impact of a mating‐induced behavioural switch on mating and subsequent oviposition activity.

Irradiation of Adult Epiphyas postvittana (Lepidoptera: Tortricidae): Egg Sterility in Parental and F1 Generations

ABSTRACT Adult Epiphyas postvittana Walker were irradiated using a Cobalt 60 source to determine the dose needed to achieve complete egg sterility of mated female moths, and egg sterility of female moths mated to F1 generation males. Adult male and female E. postvittana were irradiated at 100, 200, 250, and 300 Gy and their fertility (when crossed with normal moths) was compared with nonirradiated moths. Viable progeny (determined by egg hatch) were found at doses of 100 and 200 Gy, but very little at 250 and 300 Gy. In particular, there was no survival of female progeny into the F1 generation. Males irradiated at 250 and 300 Gy had very low egg eclosion rates (2.25 and 1.86% at 250 and 300 Gy, respectively) when mated with normal females. The F2 generation from those male progeny had a mean percent hatched of <1.02%. Based on our results, a dose of 250–300 Gy is recommended for irradiation of E. postvittana adults used for sterile insect technique (SIT) if sterility of parental moths is the desired outcome. Our data also suggests that inclusion of F1 hybrid sterility rather than parental generation sterility into programs using the SIT may allow for doses lower than what we have reported, especially during initial phases of an eradication program where increase fitness of moths might be desirable. Further research is needed to verify the use of F1 hybrid sterility in light brown apple moth SIT programs.

Trap capture of three economically important fruit fly species (Diptera: Tephritidae): evaluation of a solid formulation containing multiple male lures in a Hawaiian coffee field.

ABSTRACT Invasive fruit flies (Diptera: Tephritidae) pose a global threat to agriculture through direct damage to food crops and the accompanying trade restrictions that often result. Early detection is vital to controlling fruit flies, because it increases the probability of limiting the growth and spread of the invasive population and thus may greatly reduce the monetary costs required for eradication or suppression. Male-specific lures are an important component of fruit fly detection, and three such lures are used widely: trimedlure (TML), cue lure (CL), and methyl eugenol (ME), attractive to Mediterranean fruit fly, Ceratitis capitata (Wiedemann); melon fly, Bactrocera Cucurbitae (Coquillett); and oriental fruit fly, Bactrocera dorsalis (Hendel), respectively. In California, Florida, and Texas, the two Bactrocera lures are applied to separate species-specific traps as liquids (with a small amount of the insecticide naled added), whereas TML is delivered as a solid plug in another set of traps. Thus, the detection protocol involves considerable handling time as well as potential contact with a pesticide. The purpose of this study was to compare trap capture between liquid male lures and “trilure” wafers that contain TML, ME, raspberry ketone (RK, the hydroxy equivalent of CL), and the toxicant DDVP embedded within a solid matrix. Field studies were conducted in a Hawaiian coffee (Coffea arabica L.) field where the three aforementioned species co-occur, showed that the wafer captured at least as many flies as the liquid baits for all three species. This same result was obtained in comparisons using both fresh and aged (6-wk) baits. Moreover, the wafers performed as well as the single-lure traps in an ancillary experiment in which TML plugs were substituted for liquid TML. Additional experiments demonstrated explicitly that the presence of ME and RK had no effect on captures of C. capitata males and similarly that the presence of TML had no effect on the capture of B. Cucurbitae or B. dorsalis males.

Release-Recapture of Bactrocera Fruit Flies (Diptera: Tephritidae): Comparing the Efficacy of Liquid and Solid Formulations of Male Lures in Florida, California and Hawaii

ABSTRACT Invasive species of Bactrocera fruit flies (Diptera: Tephritidae), particularly B. dorsalis (Hendel) and B. Cucurbitae (Coquillett), pose serious threats to agricultural crops. Detection relies largely on traps baited with the male lures methyl eugenol (ME), which is attractive to B. dorsalis, and cue-lure (CL) or the related chemicals raspberry ketone (RK) and raspberry ketone formate (RKF), which are all attractive to B. Cucurbitae. Currently, ME and CL are applied as liquids to cotton wicks (along with an insecticide), a procedure involving considerable handling time and exposure to pesticides. Recent studies have shown that traps baited with solid dispensers (plugs or wafers) of male lures, which arrive in sealed envelopes ready for use, catch at least as many Bactrocera males as traps baited with liquid lures. The present study compared captures of B. dorsalis and B. Cucurbitae males in traps baited with liquid lures versus traps baited with lure-bearing solid dispensers in Florida, California, and Hawaii. In the first 2 locations, marked, irradiated males were released at street intersections, and captures were scored at 4 trapping stations 50 m distant along the intersecting streets with various lure/dispenser combinations. In Hawaii, trap catch of wild B. dorsalis and B. Cucurbitae were compared among traps with liquid and solid formulations of the lures. Although several exceptions were observed, the overall finding was that the lure-bearing plugs and wafers captured as many or more Bactrocera males as the liquid application. Consequently, we suggest that solid dispensers could be adopted in area-wide fruit fly surveillance programs without lessening their detection sensitivity to incipient infestations. The use of solid dispensers that contain both ME and RK, in particular, could greatly reduce the number of traps required and result in considerable cost savings.

Capture of Zeugodacus cucurbitae (Diptera: Tephritidae) in Traps Baited with Torula Yeast Solution Versus Cucumber Volatile Plugs

Abstract Several species of invasive fruit flies (Diptera: Tephritidae) are among the most damaging pests of agricultural crops in the world. Detection of these pests relies primarily on traps baited with male-specific lures. Traps with protein food baits are also employed to attract females, but these baits are fairly weak, and there is considerable interest in developing more powerful lures for female tephritids. Recently, a plug that emits cucumber volatiles was developed as a lure for cucurbit-infesting species, and a recent field study showed that traps baited with these plugs attracted more females of the Australian cucurbit pest Bactrocera cucumis (French) than traps containing a protein bait. The objective of the present study was to gather additional data regarding captures of a closely related species, the melon fly, Zeugodacus cucurbitae (Coquillett), in traps baited with a torula yeast and borax (TYB) solution (a standard food lure) compared with traps baited with the cucumber volatile (CV) plug. Data collected from 5 locations on Oahu, Hawaii, showed that traps baited with the TYB solution captured significantly more melon flies than traps baited with the CV plugs. At 4 sites, where hosts were scattered, melon fly captures were relatively low, and males were trapped in significantly greater numbers than females in both TYB- and CV-baited traps. At the remaining site, hosts were very abundant, melon fly captures were high, and females were trapped in significantly greater numbers than males in both TYB- and CV-baited traps. Possible explanations for the superior performance of TYB-baited traps are discussed.

Capture of melon flies and oriental fruit flies (Diptera: Tephritidae) in traps baited with torula yeast-borax or CeraTrap in Hawaii

Summary Food baits are a key component in trapping programs to detect infestations of pest species of tephritid fruit flies (Diptera: Tephritidae). Traditionally, a torula yeast-borax slurry has been used most frequently, but the recently developed food bait CeraTrap, consisting of hydrolyzed animal protein, has proven more attractive to certain tephritids. This study compared field captures of melon flies, Zeugodacus cucurbitae (Coquillett), and oriental fruit flies, Bactrocera dorsalis (Hendel), in traps baited with torula yeast-borax or CeraTrap in an agricultural setting in Hawaii. Data show that melon flies were captured in significantly greater numbers in traps baited with torula yeast-borax than CeraTrap, while no difference in captures was noted for the oriental fruit fly between traps baited with the 2 food types.

Field Longevity and Attractiveness of Trimedlure Plugs to Male Ceratitis capitata in Florida and Hawaii

Abstract Detection of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), relies heavily on traps baited with trimedlure, a male-specific attractant. Originally used as a liquid, trimedlure is now dispensed from solid polymeric plugs that reduce volatilization and increase the effective field longevity of the lure. Many of the previous bioassays that measured trimedlure longevity were conducted in Hawaii and adopted a simple “50% rule” for trimedlure plug replacement, i.e., trimedlure plugs should be changed out when their attractiveness (trap captures of male medflies) drops below 50% that observed for fresh trimedlure liquid. The goal of the present study was to assess the field effectiveness of trimedlure plugs in Florida and apply standard statistical analyses to the trapping data. Sterile marked male medflies were released in a citrus orchard with traps containing 3 trimedlure treatments: 2 mL fresh liquid, 2 g fresh plugs, or 2 g plugs aged for intervals of 1, 2, 4, 6, 8, 10, or 12 wk. A single release of approximately 40,000 males was performed for each of the weathering intervals. Weathered trimedlure plugs were as effective as fresh lures when aged 6 wk or less, but catch was significantly reduced for plugs weathered 8 or more wk. At 8 to 12 wk, remaining trimedlure content per plug was ≤ 0.4 g. Ancillary field trials in Hawaii compared male medfly captures in traps baited with fresh 2 or 3 g trimedlure plugs, or 2 or 3 g plugs weathered for 6, 8, or 10 wk. Two and 3 g plugs weathered for 6 wk were as attractive as fresh lures, but 3 g plugs were more effective than 2 g plugs at the longer weathering intervals. Results are compared with prior studies, and implications for medfly management strategies are discussed.