Invasion of Rugose spiraling whitefly (Hemiptera: Aleyrodidae) across Bangladesh coastal region causes widespread damage to coconut plants

Rugose spiraling whitefly (RSW), Aleurodicus rugioperculatus Martin, a native pest of coconut in Central America, has recently been introduced to South-East Asia. Little is known about the spread of RSW in Bangladesh, the effect this pest has on coconut plants, or the full range of its plant hosts. To fill this knowledge gap, we conducted surveys across the southern coastal coconut producing region of Bangladesh. Coconut plant damage from RSW was high throughout all the areas surveyed, and this was correlated with the population density of RSW. Areas, such as Khulna, which had the highest population density of RSW, had the highest level of RSW leaf damage. Coconut plants with an infestation of RSW had significantly fewer leaves and fruits. The coconut fruits were also smaller, both in terms of size and weight, and contained less water and lighter endosperm compared to non-infested plants. This highlights the need for the management of RSW in coconut growing regions. We also report 39 new host plant species for RSW from 22 plant families, including the economically important mangrove plant Nipa palm, Nypa fruticans Wurmb.

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.

The potential global distribution of the papaya mealybug, Paracoccus marginatus, a polyphagous pest

BACKGROUND

The papaya mealybug, Paracoccus marginatus, is a highly polyphagous invasive pest that affects more than 200 plants, many of which are of economic importance. We modelled the potential distribution of P. marginatus using CLIMEX, a process-oriented, climate-based niche model. We combined this model with spatial data on irrigation and cropping patterns to increase the real-world applicability of the model.

RESULTS

The resulting model agreed with known distribution points for this pest and with broad areas where P. marginatus has been reported, but for which no GPS data were available. Our model highlights the potential expansion of P. marginatus into novel areas in Central and East Africa, as well as further expansion in Central America and Asia, as these areas are highly climatically suitable, and have large expanses of suitable crop hosts. It also highlights areas, such as the central and eastern states of the USA as well as the western provinces of China, that are suitable for seasonal invasions of P. marginatus.

CONCLUSION

Our results offer refined resolution on areas with high potential for invasion by P. marginatus. © 2020 Society of Chemical Industry.

Wild bacterial probiotics fed to larvae of mass-reared Queensland fruit fly [Bactrocera tryoni (Froggatt)] do not impact long-term survival, mate selection, or locomotor activity

Queensland fruit fly [Bactrocera tryoni (Froggatt), Diptera, Tephritidae] is the most devastating insect pest impacting Australian horticulture. The Sterile Insect Technique (SIT) is an important component of tephritid pest management programs. However, mass-rearing and irradiation (to render insects sterile) may reduce the fitness and performance of the insect, including the ability of sterile males to successfully compete for wild females. Manipulation of the gut microbiome, including the supplementation with bacterial probiotics shows promise for enhancing the quality of mass-reared sterile flies, however there are fewer published studies targeting the larval stage. In this study, we supplemented the larval stage of mass-reared B. tryoni with bacterial probiotics. We tested several individual bacteria that had been previously isolated and characterized from the gut of wild B. tryoni larvae including Asaia sp., Enterobacter sp., Lactobacillus sp., Leuconostoc sp. We also tested a consortium of all four of these bacterial isolates. The fitness parameters tested included adult survival in field cages, laboratory mate selection of bacteria supplemented males by bacteria nonsupplemented females, and laboratory locomotor activity of adult flies. None of the bacterial probiotic treatments in the current study was significantly different to the control for field survival, mate selection or locomotor activity of adult B. tryoni, which agree with some of the other studies regarding bacterial probiotics fed to the larval stage of tephritids. Future work is needed to determine if feeding the same, and/or other probiotics to adults, as opposed to larvae can positively impact survival, mating performance, mating competitiveness and locomotor activity of B. tryoni. The bacterial group(s) and function of bacterial species that increase fitness and competitiveness is also of interest to tephritid mass-rearing programs.

A walk on the wild side: gut bacteria fed to mass-reared larvae of Queensland fruit fly [Bactrocera tryoni (Froggatt)] influence development

BACKGROUND

The Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera, Tephritidae) is the most significant insect pest of Australian horticulture. Bactrocera tryoni is controlled using a range of tools including the Sterile Insect Technique (SIT). Mass-rearing and irradiation of pupae in SIT can reduce the fitness and quality of the released sterile insects. Studies have also showed reduced microbial gut diversity in domesticated versus wild tephritids.

RESULTS

Transmission electron microscopy confirmed the presence of the bacterial isolates in the mid-gut of mass-reared larvae, and plate counts from individual larval guts showed increased numbers of bacteria in supplemented larvae. Several developmental and fitness parameters were tested including larval development time (egg-hatch to pupation), pupal weight, emergence, flight ability, sex-ratio, and time to adult eclosion (egg-hatch to adult eclosion). Enterobacter sp. and Asaia sp. shortened larval development time, while this was delayed by Lactobacillus sp., Leuconostoc sp. and a blend of all four bacteria. The mean time from egg hatch to adult eclosion was significantly reduced by Leuconostoc sp. and the blend for males and females, indicating that the individual bacterium and consortium affect flies differently depending on the life stage (larval or pupal). There was no impact of bacterial supplemented larvae on pupal weight, emergence, flight ability, or sex ratio.

CONCLUSIONS

Our findings show that bacteria fed to the larval stage of B. tryoni can impart fitness advantages, but the selection of probiotic strains (individual or a consortium) is key, as each have varying effects on the host. Bacteria added to the larval diet particularly Leuconostoc sp. and the blend have the capacity to reduce costs and increase the number of flies produced in mass-rearing facilities by reducing time to adult eclosion by 1.3 and 0.8 mean days for males, and 1.2 and 0.8 mean days for females.

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.

Semiochemical mediated enhancement of males to complement sterile insect technique in management of the tephritid pest Bactrocera tryoni (Froggatt)

Queensland fruit fly, Bactrocera tryoni (Froggatt), is the most significant pest of Australia's $9 billion horticulture industry. The sterile insect technique (SIT) and cue-lure (a synthetic analogue of raspberry ketone (RK))-based male annihilation technique (MAT) are two of the most effective management tools against this pest. However, combining these two approaches is considered incompatible as MAT kills sterile and 'wild' males indiscriminately. In the present study we tested the effect of pre-release feeding of B. tryoni on RK on their post-release survival and response to MAT in field cages and in a commercial orchard. In both settings, survival was higher for RK supplemented adults compared to control (i.e. RK denied) adults. A lower number of RK supplemented sterile males were recaptured in MAT baited traps in both the field cages and orchard trials compared to RK denied sterile males. The advantage of this novel "male replacement" approach (relatively selective mortality of wild males at lure-baited traps while simultaneously releasing sterile males) is increasing the ratio of sterile to wild males in the field population, with potential for reducing the number of sterile males to be released.