Charlotte Aldebron

The tropical nut borer, Hypothenemus obscurus (F.) (Coleoptera: Curculionidae: Scolytinae), is a significant economic pest in Hawaii’s macadamia orchards, contributing to substantial pre- and postharvest losses. Existing management strategies relying on cultural controls and generalist predators have been proven inefficient. This study developed and evaluated a trap-based monitoring system integrating both olfactory and visual cues to improve pest monitoring and management for H. obscurus. Field trials conducted over 2 yr assessed various alcohol-based lure formulations and trap color preferences under commercial orchard conditions. Results demonstrated that lures containing higher proportions of methanol, particularly at a 100% concentration and 3:1 methanol-to-ethanol ratio, captured significantly more H. obscurus than ethanol-only lures. Trap placement at 1.5 m in the lower canopy yielded higher captures compared to ground-deployed traps. Color trials revealed that transparent bottle traps achieved the highest captures, followed by brown and red, while yellow and white traps were the least effective. In summary, methanol-baited, transparent bottle traps deployed in the lower canopy of trees proved to be most effective in capturing H. obscurus, highlighting the importance of integrating semiochemical and visual stimuli as well as trap placement to enhance trap effectiveness. The implications of our findings for the enhancement of early detection, timely interventions, and improvement of integrated pest management strategies for H. obscurus are discussed.

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a specialist of Olea fruits and is a major pest of commercial olives due to their adverse impacts to fruit quality. In support of genomic and physiological research of the olive fly, we sequenced, assembled, and annotated 2 independent genomes: one from a wild-collected male and one from a wild-collected female. The resulting genomes are highly contiguous, collinear, and complete, attesting to the accuracy and quality of both assemblies. In addition to the autosomes captured as single contigs, the X and Y chromosomes were also identified as evidenced by the X chromosome showing diploid coverage in the female assembly compared to haploid coverage in the male assembly and the Y chromosome being entirely absent from the female assembly. These assemblies represent the first full chromosome-level assembly for olive fly. In addition, a complete genome assembly of a known obligate symbiont, Candidatus Erwinia dacicola, was fully sequenced. The Ca. E. dacicola genome we report here is the most contiguous to date, represented by a gapless chromosome and 2 separate gapless plasmids. These genome assemblies, along with bacterial symbiont assembly, provide foundational resources for future genetic and genomic research in support of its management as an agricultural pest.

Behavioral differences between related insects may inform how pest management strategies or conservation efforts are tailored to specific species. Movement behavior is particularly important, but few studies have undertaken head-to-head comparisons to evaluate differences in interspecific movement. This study used harmonic radar to simultaneously track 2 agriculturally important tephritid fruit fly species, Bactrocera dorsalis (Hendel) and Ceratitis capitata (Wiedemann), in an outdoor cage (experiment 1) and a coffee field (experiments 2 and 3) to assess fly directional movement, distance, and speed parameters. In general, both fly species have similar movement parameters. However, experiment 2 showed B. dorsalis to be more active with fewer induced movements and less time needed to record the target number of movement steps. This was supported by a laboratory bioassay (experiment 4) that confirmed B. dorsalis were more active. Mean step-distances only differed in experiment 2 and were longer for C. capitata. Experiment 3 tracked tagged flies over time with 2 B. dorsalis located after 3 d post-release while no C. capitata were located after 48 h. Both species generally move with the prevailing wind. While this study found some differences in movement behaviors between these 2 fly pests, fly movement parameters were more similar than expected, suggesting that it may be possible to characterize the movement of key insect species and then generalize these findings to related taxa. If this is possible, control and detection strategies optimized with movement data from one species may be transferable to other pests, thereby increasing the impact of movement research.

Tephritid fruit flies are invasive species of ripening fruit and vegetables. The olive fly ( Bactrocera oleae ) a specialist of olives, harbors a symbiotic gut bacterium Candidatus Erwinia dacicola , which is crucial to the olive fly’s exploitation of Oleaceae . This study characterized the genome of Ca. E. dacicola to investigate functional pathways that facilitate its obligate symbiosis. We used an extremely high-quality Ca. E. dacicola genome produced in tandem with an olive fly genome and paired that reference with transcriptomics. Of 4,675 genes, 1,783 (38.13%) were classified as pseudogenes. Overall, many pathways are complete, mostly associated with nutritional components. The symbiont also has genes encoding hypothetical proteins to degrade the phenolics in olives. Some pathways were heavily pseudogeneized, suggesting that Ca. E. dacicola have impaired functions in generalized metabolism, carbon utilization, pathogenicity, and signaling systems. Gene selection analyses in Ca. E. dacicola compared to related organisms, indicated positive selection on genes related to amino acid metabolism, carbon utilization, secretion and transport, and energy production. Our results indicate that the main service likely provided by Ca. E. dacicola is the production of amino acids and metabolism of oleuropein. The high pseudogenization rate implies incipient erosion of a formerly free-living symbiont.

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a specialist of fruits of the genus Olea and is a major pest of commercial olives due to their adverse impacts to olive production. In support of genomic and physiological research of the olive fly, we sequenced, assembled, and annotated two independent genomes, one from a wild-collected male and one from a wild-collected female. The resulting genomes are highly contiguous, collinear, and complete, attesting to the accuracy and quality of both assemblies. In addition to the autosomes captured as single contigs, the X and Y chromosomes were also captured as evidenced by the X chromosome showing diploid coverage in the female assembly compared to haploid coverage in the male assembly and the Y chromosome being entirely absent from the female assembly. These assemblies represent the first full chromosome-level assembly for Olive fly . In addition, a complete genome assembly of a known obligate symbiont to the olive fly, Candidatus Erwinia dacicola , was fully captured. The Ca. E. dacicola we report here is the most contiguous to date, represented with a gapless chromosome and two separate gapless plasmids. These genome assemblies, along with bacterial symbiont assembly, provide foundational resources for future genetic and genomic research in support of its management as an agricultural pest.

The Male Annihilation Technique (also termed the Male Attraction Technique; “MAT”) is often used to eradicate pestiferous tephritid fruit flies, such as Bactrocera dorsalis (Hendel). MAT involves the application of male-specific attractants combined with an insecticide in spots or stations across an area to reduce the male population to such a low level that suppression or eradication is achieved. Currently, implementations of MAT in California and Florida targeting B. dorsalis utilize the male attractant methyl eugenol (ME) accompanied with a toxicant, such as spinosad, mixed into a waxy, inert emulsion STATIC ME (termed here “SPLAT-MAT-ME”). While highly effective against ME-responding species, such applications are expensive owing largely to the high cost of the carrier matrix and labor for application. Until recently the accepted protocol called for the application of approximately 230 SPLAT-MAT-ME spots per km²; however, findings from Hawaii suggest a lower density may be more effective. The present study adopted the methods of that earlier work and estimated kill rates of released B. dorsalis under varying spot densities in areas of California and Florida that have had recent incursions of this invasive species. Specifically, we directly compared trap captures of sterilized marked B. dorsalis males released in different plots under three experimental SPLAT-MAT-ME densities (50, 110, and 230 per km²) in Huntington Beach, CA; Anaheim, CA; and Sarasota-Bradenton, FL. The plots with a density of 110 sites per km² had a significantly higher recapture proportion than plots with 50 or 230 sites per km². This result suggests that large amounts of male attractant may reduce the ability of males to locate the source of the odor, thus lowering kill rates and the effectiveness of eradication efforts. Eradication programs would directly benefit from reduced costs and improved eradication effectiveness by reducing the application density of SPLAT-MAT-ME.