Additive Effect of Releasing Sterile Insects Plus Biocontrol Agents against Fruit Fly Pests (Diptera: Tephritidae) under Confined Conditions

Pest control models integrating the use of the sterile insect technique (SIT) and augmentative biological control (ABC) have postulated that it is possible to obtain a synergistic effect from the joint use of these technologies. This synergistic effect is attributed to the simultaneous attack on two different biological stages of the pest (immature and adult flies), which would produce higher suppression on the pest populations. Here we evaluated the effect of the joint application of sterile males of A. ludens of the genetic sexing strain Tap-7 along with two parasitoid species at the field cage level. The parasitoids D. longicaudata and C. haywardi were used separately to determine their effect on the suppression of the fly populations. Our results showed that egg hatching percentage was different between treatments, with the highest percentage in the control treatment and a gradual reduction in the treatments with only parasitoids or only sterile males. The greatest induction of sterility (i.e., the lowest egg hatching percentage) occurred with the joint use of ABC and SIT, demonstrating that the earlier parasitism caused by each parasitoid species was important reaching high levels of sterility. Gross fertility rate decreased up to 15 and 6 times when sterile flies were combined with D. longicaudata and C. haywardi, respectively. The higher parasitism by D. longicaudata was determinant in the decrease of this parameter and had a stronger effect when combined with the SIT. We conclude that the joint use of ABC and SIT on the A. ludens population had a direct additive effect, but a synergistic effect was observed in the parameters of population dynamics throughout the periodic releases of both types of insects. This effect can be of crucial importance in the suppression or eradication of fruit fly populations, with the added advantage of the low ecological impact that characterizes both techniques.

Manipulating Insect Sex Determination Pathways for Genetic Pest Management: Opportunities and Challenges

Sex determination pathways in insects are generally characterised by an upstream primary signal, which is highly variable across species, and that regulates the splicing of a suite of downstream but highly-conserved genes (transformer, doublesex and fruitless). In turn, these downstream genes then regulate the expression of sex-specific characteristics in males and females. Identification of sex determination pathways has and continues to be, a critical component of insect population suppression technologies. For example, "first-generation" transgenic technologies such as fsRIDL (Female-Specific Release of Insects carrying Dominant Lethals) enabled efficient selective removal of females from a target population as a significant improvement on the sterile insect technique (SIT). Second-generation technologies such as CRISPR/Cas9 homing gene drives and precision-guided SIT (pgSIT) have used gene editing technologies to manipulate sex determination genes in vivo. The development of future, third-generation control technologies, such as Y-linked drives, (female to male) sex-reversal, or X-shredding, will require additional knowledge of aspects of sexual development, including a deeper understanding of the nature of primary signals and dosage compensation. This review shows how knowledge of sex determination in target pest species is fundamental to all phases of the development of control technologies.

Lysenko and the Screwworm Fly-When Politics Interferes with Science and Public Health

In the One Health scenario, a deep understanding of the dynamics potentially threatening the development and implementation of useful pest and vector management tools is of key importance. The New World screwworm fly, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), is characterized by a wide host range. It acts as an important agent of myiasis in humans and warm-blooded animals in the Neotropics, and has been eliminated from a wide region through genetic methods. Of note, Serebrovsky had already proposed in 1940 the principles of autocidal control by the translocation of segments between two chromosomes, but his work was negated by Lysenko, based on the negation of Mendelian genetics. This entomological case study emphasizes the danger of politics interfering with science, a still contemporary hot issue. The negation of global warming or current pandemics are further examples of this noxious influence.

Raspberry ketone accelerates sexual maturation and improves mating performance of sterile male Queensland fruit fly, Bactrocera tryoni (Froggatt)

BACKGROUND

Tephritid fruit flies are recognized as the most economically important insect pest group, causing significant losses to horticultural crops globally. The sterile insect technique (SIT) is used to suppress or eradicate pest fruit flies in many countries. The provisioning of adult dietary or olfactory supplementation pre-release is commonly used to improve the mating performance of sterile male flies in SIT. This study on a major pest species, Queensland fruit fly, Bactrocera tryoni (Froggatt), focused on improving mating performance by providing a semiochemical, raspberry ketone (RK), in the pre-release adult diet.

RESULTS

Survival was numerically higher for RK-supplemented males. Sexual maturity occurred 1 day earlier (from 7 to 6 days) in RK-supplemented sterile males. The mating latency period decreased with maturation age and was lower for RK-fed males. RK-supplemented sterile males increasingly mated with fertile females as they aged (10-19 days). The mating competitiveness of both RK-supplemented sterile males and RK-denied sterile males was greater than that of wild males.

CONCLUSION

The early sexual maturity and increased mating performance of RK-supplemented sterile males indicate that the effectiveness of SIT programmes can be increased through dietary supplementation with RK during the pre-release period. © 2018 Society of Chemical Industry.

Comparison of Efficiency of BG-Sentinel Traps Baited with Mice, Mouse-Litter, and CO₂ Lures for Field Sampling of Male and Female Aedes albopictus Mosquitoes

Determining the abundance and distribution of male mosquitoes in the wild and establishing species seasonality in candidate pilot sites is of particular interest with respect to the use of the sterile-male technique. With the knowledge that using mice as bait in BG-Sentinel traps effectively enhances Aedes albopictus male and female trapping success, the present study was designed to determine whether attractants derived from mouse odour blend could be a viable substitute for live mice to lure Ae. albopictus mosquitoes into traps. The effects of baiting BG-Sentinel traps with mice, carbon dioxide (CO₂), and attractants derived from litter mouse odours (mouse litter (ML)) and a mouse odour blend (MOB) on the efficiency of trapping Ae. albopictus males and females were tested using a Latin square design. The BG-Sentinel trap baited with CO₂ + ML caught a significantly larger number of mosquitoes compared to traps baited with mice only. The BG-Sentinel traps containing only CO₂ or CO₂ + MOB, however, did not catch significantly more mosquitoes compared to the other traps. The proportions of males caught in the BG-Sentinel traps did not differ significantly between the respective attractants. The results from this study confirm that CO₂ bait is efficient to provide a reliable estimation method for Ae. albopictus adult male abundance in the wild, and suggest that mouse litter baits in combination with CO₂ could be used to enhance Aedes trapping success in BG-Sentinel traps.