Recaptures of feral Bactrocera dorsalis and B. umbrosa (Diptera: Tephritidae) males after feeding on methyl eugenol

A Limiting Factor of Sex Attractants of Bactrocera dorsalis (Diptera: Tephritidae), Verified under Laboratory Conditions

At present, sexual attractants mainly control insect populations by killing males. However, the effect of sex attractants may be limited by the mating ability of the attracted insects. The Oriental fruit fly, Bactrocera dorsalis (Hendel), has a strong reproductive capacity; it brings great losses to agricultural production, which can be controlled by methods using sex attractant methyl eugenol that mainly attracts males. Therefore, we studied the multiple and continuous (as well as consecutive) mating ability of B. dorsalis through behavioral experiments. The results show that male B. dorsalis can mate 11 times on average, with females mating only 1.93 times, and that 10.81% of males mate more than 20 times. The reproductive capacity of male B. dorsalis decreased significantly after four to five instances of continuous mating. In different mating patterns, the reproductive fitness of polyandry is not the highest, rather, interval mating is the best. A limiting factor of the sex attractant effect was revealed in B. dorsalis through behavioral evidence.

Potential of Fruit Extracts as Attractants of Female Oriental Fruit Flies

<b>Background and Objective:</b> The oriental fruit fly <i>Bactrocera dorsalis</i> (Hendel) is one of the most important insect pest species of fruit and vegetable crops in the tropical and subtropical regions. This study aimed to determine the attraction of female and male <i>B. dorsalis</i> fruit flies to the aroma of fruit juice from the host plants as well as their attraction to methanol extract, ethyl acetate extract and distillate water of selected host fruits. <b>Materials and Methods:</b> The attractiveness of the juice and extract/distillate water of the host fruits to <i>B. dorsalis</i> fruit flies was carried out in an experimental cage measuring 200×200×200 cm that was placed in the laboratory. The volatile compounds in the juice, methanol extract, ethyl acetate extract and distillate water of the selected fruits were analyzed using GCMS-Pyrolysis. <b>Results:</b> The results show that among the eight fruit juice aromas tested, the ones that significantly affected the number of trapped female <i>B. dorsalis</i> were the aromas of banana juice, papaya juice and chilli juice. The results of the analysis by GCMS-Pyrolysis showed that the methanol extract of banana fruit contains one volatile compound that was previously reported to have the ability to attract female <i>B. dorsalis</i> fruit flies. Two volatile compounds in the banana distillate water were also reported to have the ability to attract female <i>B. dorsalis</i> and other fruit flies. <b>Conclusion:</b> From the results of this study, it can be concluded that the methanol extract and distillate water of the green <i>Ambon lumut</i> banana fruit of <i>Musa acuminata</i> Colla has the potential to be developed as an attractant of female <i>B. dorsalis</i>.

Raspberry ketone diet supplement reduces attraction of sterile male Queensland fruit fly to cuelure by altering expression of chemoreceptor genes

Sterile male Queensland fruit fly, Bactrocera tryoni (Froggatt), fed as immature adults on the plant compound raspberry ketone (RK), show a reduced attraction to cuelure, a synthetic analogue of RK used as an attractant in Male Annihilation Technique. We hypothesized the reduced attraction of RK-fed adult males to cuelure may be a consequence of altered expression of chemoreception genes. A Y-tube olfactometer assay with RK-fed and RK-unfed sterile B. tryoni males tested the subsequent behavioural response to cuelure. Behavioral assays confirmed a significant decrease in attraction of RK-fed sterile males to cuelure. RK-fed, non-responders (to cue-lure) and RK-unfed, responders (to cue-lure) males were sampled and gene expression compared by de novo RNA-seq analysis. A total of 269 genes in fly heads were differentially expressed between replicated groups of RK-fed, cuelure non-responders and RK-unfed, cuelure responders. Among them, 218 genes including 4 chemoreceptor genes were up regulated and 51 genes were down regulated in RK-fed, cuelure non-responders. De novo assembly generated many genes with unknown functions and no significant BLAST hits to homologues in other species. The enriched and suppressed genes reported here, shed light on the transcriptional changes that affect the dynamics of insect responses to chemical stimuli.

Evaluation of a Genetic Sexing Strain of the Oriental Fruit Fly as a Candidate for Simultaneous Application of Male Annihilation and Sterile Insect Techniques (Diptera: Tephritidae)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is an important pest of fruits and vegetables, and many countries operate surveillance programs to detect infestations and, if needed, implement costly control efforts. The Male Annihilation Technique (MAT), which involves deployment of the male lure methyl eugenol (ME) to reduce or eliminate the male population, has been used as a stand-alone strategy or as a precursor to the Sterile Insect Technique (SIT), which involves the release of sterile males to generate sterile male by wild female crosses and the production of inviable progeny. Modeling suggests that simultaneous implementation of MAT and SIT, rather than sequential deployment, increases the probability of successful eradication. Previous research has shown that B. dorsalis males that have fed on ME show reduced tendency to re-visit ME sources. Also, males fed ME gain a mating advantage over nonfed males. The goal of the present study was to evaluate the suitability of a genetic sexing strain of B. dorsalis as a candidate for concurrent implementation of MAT and SIT. Evaluation focused on the timing of prerelease exposure to methyl eugenol to identify the male age at which feeding upon the lure both i) reduces postrelease attraction to ME-baited traps (thus allowing the operation of MAT) and ii) enhances postrelease mating competitiveness (thus increasing the effectiveness of SIT). Results indicate that prerelease ME feeding by 6-d-old males, with release the following day, would allow effective, concurrent implementation of MAT and SIT.