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Insects, Volume 10, Issue 12 (December 2019) – 41 articles

Cover Story (view full-size image): The Nazgȗl is a lure and kill system proposed for use as a tool in future eradication efforts against brown marmorated stink bug (BMSB) in new jurisdictions such as New Zealand, where eradication might be possible. It is based on an IPM tool developed in the USA called “ghost nets” and combines an insecticide-treated net and aggregation pheromone with a synergist, which is suspended using a coat hanger from tree branches, with a catch tray at the base. These traps caught and killed all mobile life stages of BMSB. The name is derived from J.R.R. Tolkein’s sinister-looking ringwraiths and is designed to elicit public support for biosecurity in a new way, tapping into popular culture around saving “Middle-earth”. View this paper
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Review
Context-Dependence and the Development of Push-Pull Approaches for Integrated Management of Drosophila suzukii
Insects 2019, 10(12), 454; https://doi.org/10.3390/insects10120454 - 15 Dec 2019
Cited by 9 | Viewed by 2168
Abstract
Sustainable pest control requires a systems approach, based on a thorough ecological understanding of an agro-ecosystem. Such fundamental understanding provides a basis for developing strategies to manipulate the pest’s behaviour, distribution, and population dynamics, to be employed for crop protection. This review focuses [...] Read more.
Sustainable pest control requires a systems approach, based on a thorough ecological understanding of an agro-ecosystem. Such fundamental understanding provides a basis for developing strategies to manipulate the pest’s behaviour, distribution, and population dynamics, to be employed for crop protection. This review focuses on the fundamental knowledge required for the development of an effective push-pull approach. Push-pull is a strategy to repel a pest from a crop, while attracting it toward an external location. It often relies on infochemicals (e.g., pheromones or allelochemicals) that are relevant in the ecology of the pest insect and can be exploited as lure or repellent. Importantly, responsiveness of insects to infochemicals is dependent on both the insect’s internal physiological state and external environmental conditions. This context-dependency reflects the integration of cues from different sensory modalities, the effect of mating and/or feeding status, as well as diurnal or seasonal rhythms. Furthermore, when the costs of responding to an infochemical outweigh the benefits, resistance can rapidly evolve. Here, we argue that profound knowledge on context-dependence is important for the development and implementation of push-pull approaches. We illustrate this by discussing the relevant fundamental knowledge on the invasive pest species Drosophila suzukii as an example. Full article
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Article
Effects of Detritivores on Nutrient Dynamics and Corn Biomass in Mesocosms
Insects 2019, 10(12), 453; https://doi.org/10.3390/insects10120453 - 13 Dec 2019
Cited by 1 | Viewed by 1296
Abstract
(1) Background: Strategies aimed at managing freshwater eutrophication should be based on practices that consider cropland invertebrates, climatic change, and soil nutrient cycling. Specifically, detritivores play a crucial role in the biogeochemical processes of soil through their consumptive and burrowing activities. Here, we [...] Read more.
(1) Background: Strategies aimed at managing freshwater eutrophication should be based on practices that consider cropland invertebrates, climatic change, and soil nutrient cycling. Specifically, detritivores play a crucial role in the biogeochemical processes of soil through their consumptive and burrowing activities. Here, we evaluated the effectiveness of increasing detritivore abundance as a strategy for nutrient management under varied rainfall. (2) Methods: We manipulated soil macroinvertebrate abundance and rainfall amount in an agricultural mesocosms. We then measured the phosphorus, nitrogen, and carbon levels within the soil, corn, invertebrates, and soil solution. (3) Results: Increasing detritivore abundance in our soil significantly increased corn biomass by 2.49 g (p < 0.001), reduced weed growth by 18.2% (p < 0.001), and decreased soil solution nitrogen and total organic carbon (p < 0.05) and volume by 31.03 mL (p < 0.001). Detritivore abundance also displayed a significant interaction effect with rainfall treatment to influence soil total P (p = 0.0019), total N (p < 0.001), and total C (p = 0.0146). (4) Conclusions: Soil detritivores play an important role in soil nutrient cycling and soil health. Incorporating soil macroinvertebrate abundance into management strategies for agricultural soil may increase soil health of agroecosystems, preserve freshwater ecosystems, and protect the valuable services they both provide for humans. Full article
(This article belongs to the Special Issue Elucidating the Role of Soil Arthropods in Soil Health)
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Article
The Effects of a Cold Disinfestation on Bactrocera dorsalis Survival and Navel Orange Quality
Insects 2019, 10(12), 452; https://doi.org/10.3390/insects10120452 - 13 Dec 2019
Cited by 5 | Viewed by 1059
Abstract
Citrus sinensis (L.) Osbeck is an important economic product in South China, but the presence of quarantine pests in this product proposes the potential threat to international trade security. To find a proper phytosanitary cold treatment for Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), [...] Read more.
Citrus sinensis (L.) Osbeck is an important economic product in South China, but the presence of quarantine pests in this product proposes the potential threat to international trade security. To find a proper phytosanitary cold treatment for Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), commonly called oriental fruit fly, one of the most serious quarantine insects in navel orange, eggs in petri dish and larvae in navel orange fruits were exposed to a 1.7 °C cold chamber for 0–11 days to compare the tolerance to cold treatment. The 2nd instar larva (4 days) is the most tolerant stage, and the estimated time for 99.9968% mortality at the 95% confidence level is 11.3 (9.5, 14.6) days. Then 15 days was selected as the target time for the confirmatory tests, resulting in no survivors from 37,792 treated larvae with the efficacy of 99.9921% mortality at the 95% confidence level. The quality assessments were conducted to compare the effect on the navel orange fruit between cold treatment and the conventional cold storage. Results indicated that the cold treatment did not negatively affect the fruit quality. Therefore, this cold treatment showed potential as a commercial quarantine treatment for navel orange in international trade. Full article
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Article
Electrophysiological and Alarm Responses of Solenopsis invicta Buren (Hymenoptera: Formicidae) to 2-Ethyl-3,5-dimethylpyrazine
Insects 2019, 10(12), 451; https://doi.org/10.3390/insects10120451 - 13 Dec 2019
Cited by 3 | Viewed by 1399
Abstract
2-Ethyl-3,5-dimethylpyrazine is an isomer of 2-ethyl-3,6-dimethylpyrazine, the alarm pheromone component of the red imported fire ant, Solenopsis invicta Buren. The pyrazine was synthesized and its alarm activity was investigated under laboratory conditions. It elicited significant electroantennogram (EAG) activities, and released characteristic alarm behaviors [...] Read more.
2-Ethyl-3,5-dimethylpyrazine is an isomer of 2-ethyl-3,6-dimethylpyrazine, the alarm pheromone component of the red imported fire ant, Solenopsis invicta Buren. The pyrazine was synthesized and its alarm activity was investigated under laboratory conditions. It elicited significant electroantennogram (EAG) activities, and released characteristic alarm behaviors in fire ant workers. The EAG and alarm responses were both dose-dependent. Two doses of the pyrazine, 1 and 100 ng, were further subjected to bait discovery bioassays. Fire ant workers excited by the pyrazine were attracted to food baits, and their numbers increased over time. Ants displayed very similar response patterns to both low and high doses of the pyrazine. The pyrazine impregnated onto filter paper disc attracted significantly more fire ant workers than the hexane control for all observation time intervals at the low dose, and in the first 15 min period at the high dose. The pyrazine loaded onto food bait directly tended to attract more fire ant workers than the hexane control. These results support the potential use of 2-ethyl-3,5-dimethylpyrazine to enhance bait attractiveness for the control of S. invicta in invaded regions. Full article
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Article
Microsatellite Marker Discovery in the Stingless Bee Uruçu-Amarela (Melipona rufiventris Group, Hymenoptera, Meliponini) for Population Genetic Analysis
Insects 2019, 10(12), 450; https://doi.org/10.3390/insects10120450 - 13 Dec 2019
Viewed by 1204
Abstract
The species Melipona rufiventris Lepeletier, 1836 is a Brazilian native stingless bee that is part of a species complex known as the ‘rufiventris group’, making it difficult to distinguish between the different species. Populations in this group are facing a severe decline, [...] Read more.
The species Melipona rufiventris Lepeletier, 1836 is a Brazilian native stingless bee that is part of a species complex known as the ‘rufiventris group’, making it difficult to distinguish between the different species. Populations in this group are facing a severe decline, leading to the risk of local extinction, and therefore, their conservation should be treated as a major concern. This study describes the first set of tri- and tetranucleotide microsatellite markers, using next-generation sequencing technology for use in the identification of genetic diversity and population structure in the ‘rufiventris group’. A total of 16 microsatellite loci displayed polymorphism. Analysis of the whole data set (n = 50) detected 63 alleles in all loci, ranging from 2 to 7 with a mean of 3.9 alleles/locus. A genetic diversity analysis revealed high values for population differentiation estimates (FST = 0.252, RST = 0.317, and DEST = 0.284) between the Atlantic Forest, Cerrado, and Caatinga biomes. An additional evidence for genetic divergence among populations was also found in the ’rufiventris group’; these should be treated as separate conservation units or even as separate species. These microsatellite markers have demonstrated a strong potential for assessing population discrimination in this threatened stingless bee group. Full article
(This article belongs to the Special Issue Population Genetics of Insects)
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Article
Response to Multiple Stressors: Enhanced Tolerance of Neoseiulus barkeri Hughes (Acari: Phytoseiidae) to Heat and Desiccation Stress through Acclimation
Insects 2019, 10(12), 449; https://doi.org/10.3390/insects10120449 - 13 Dec 2019
Cited by 6 | Viewed by 1019
Abstract
Organisms are always confronted with multiple stressors simultaneously. Combinations of stressors, rather than single stressor, may be more appropriate in evaluating the stress they experience. N. barkeri is one of predatory mite species that are commercialized for controlling spider mites. However, their biological [...] Read more.
Organisms are always confronted with multiple stressors simultaneously. Combinations of stressors, rather than single stressor, may be more appropriate in evaluating the stress they experience. N. barkeri is one of predatory mite species that are commercialized for controlling spider mites. However, their biological control efficiency was often reduced because of high temperature and desiccation in summer. To understand how to improve the tolerance of N. barkeri to combined heat and desiccation stress, we pre-exposed the adult female of N. barkeri to high temperature, desiccation and high temperature × desiccation stress for acclimation. After proper recovery time, mites were subjected to high temperature × desiccation stress again to detect the acclimation effects. The results are as follows: (1) No decrease in mortality rate were observed under high temperature × desiccation stress after heat acclimation. Instead, it increased significantly with acclimation temperature and time. (2) Dehydration acclimation both at 25 °C and high temperatures reduced mortality rate under high temperature × desiccation stress. Mortality rate was only significantly correlated with the amount of water loss, but not with temperature or water loss rate in acclimation, suggesting the increased tolerance is related to dehydration stress rather than heat stress. Among all acclimations, chronic dehydration at 25 °C, 50% relative humidity were the most effective treatment. This study indicated dehydration acclimation is effective to enhance tolerance of N. barkeri to combined heat and desiccation stress, which can improve the efficiency of biological control under multiple stressors. Full article
(This article belongs to the Special Issue Insects-Environment Interaction)
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Article
Mass-Rearing of Drosophila suzukii for Sterile Insect Technique Application: Evaluation of Two Oviposition Systems
Insects 2019, 10(12), 448; https://doi.org/10.3390/insects10120448 - 12 Dec 2019
Cited by 12 | Viewed by 1851
Abstract
Drosophila suzukii (Diptera: Drosophilidae) is an invasive pest of a wide range of commercial soft-skinned fruits. To date, most management tactics are based on spraying of conventional and/or organic insecticides, baited traps, and netting exclusion. Interest has been expressed in using the sterile [...] Read more.
Drosophila suzukii (Diptera: Drosophilidae) is an invasive pest of a wide range of commercial soft-skinned fruits. To date, most management tactics are based on spraying of conventional and/or organic insecticides, baited traps, and netting exclusion. Interest has been expressed in using the sterile insect technique (SIT) as part of area-wide integrated pest management (AW-IPM) programs to control D. suzukii infestations. Mass-rearing protocols are one of the prerequisites for successful implementation of the SIT. To establish mass-rearing methods for this species, two different egg-collection systems were developed and compared with respect to the number of eggs produced, egg viability, pupa and adult recovery, adult emergence rate, and flight ability. Female flies kept in cages equipped with a wax panel produced significantly more eggs with higher viability and adult emergence rate, as compared to the netted oviposition system. The wax panel system was also more practical and less laborious regarding the collection of eggs. Furthermore, the wax panel oviposition system can be adapted to any size or design of an adult cage. In conclusion, this system bears great promise as an effective system for the mass production of D. suzukii for SIT. Full article
(This article belongs to the Special Issue Sterile Insect Technique (SIT) and Its Applications)
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Article
New Species-Specific Primers for Molecular Diagnosis of Bactrocera minax and Bactrocera tsuneonis (Diptera: Tephritidae) in China Based on DNA Barcodes
Insects 2019, 10(12), 447; https://doi.org/10.3390/insects10120447 - 12 Dec 2019
Cited by 1 | Viewed by 1039
Abstract
Tephritidae fruit flies (Diptera: Tephritidae) are regarded as important damage-causing species due to their ability to cause great economic losses in fruit and vegetable crops. Bactrocera minax and Bactrocera tsuneonis are two sibling species of the subgenus Tetradacus of Bactrocera that are distributed [...] Read more.
Tephritidae fruit flies (Diptera: Tephritidae) are regarded as important damage-causing species due to their ability to cause great economic losses in fruit and vegetable crops. Bactrocera minax and Bactrocera tsuneonis are two sibling species of the subgenus Tetradacus of Bactrocera that are distributed across a limited area of China, but have caused serious impacts. They share similar morphological characteristics. These characteristics can only be observed in the female adult individuals. The differences between them cannot be observed in preimaginal stages. Thus, it is difficult to distinguish them in preimaginal stages morphologically. In this study, we used molecular diagnostic methods based on cytochrome c oxidase subunit I and species-specific markers to identify these two species and improve upon the false-positive results of previous species-detection primers. DNA barcode sequences were obtained from 900 individuals of B. minax and 63 individuals of B. tsuneonis. Based on these 658 bp DNA barcode sequences of the cytochrome c oxidase subunit I gene, we successfully designed the species-specific primers for B. minax and B. tsuneonis. The size of the B. minax specific fragment was 422 bp and the size of the B. tsuneonis specific fragment was 456 bp. A series of PCR trials ensured the specificity of these two pairs of primers. Sensitivity assay results demonstrated that the detection limit for the DNA template concentration was 0.1~1 ng/μL for these two species. In this study, we established a more reliable, rapid, and low-cost molecular identification method for all life stages of B. minax and B. tsuneonis. Species-specific PCR can be applied in plant quarantine, monitoring and control of B. minax and B. tsuneonis. Full article
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Article
The Response of Neotropical Dragonflies (Insecta: Odonata) to Local and Regional Abiotic Factors in Small Streams of the Amazon
Insects 2019, 10(12), 446; https://doi.org/10.3390/insects10120446 - 12 Dec 2019
Cited by 17 | Viewed by 1800
Abstract
Since the relative role of local and regional abiotic factors on the Odonata diversity in rainforest streams is still poorly understood, we evaluated the effects of these factors on adult Odonata (Insecta) from preserved and altered streams in the Amazonian region. Adult Odonata [...] Read more.
Since the relative role of local and regional abiotic factors on the Odonata diversity in rainforest streams is still poorly understood, we evaluated the effects of these factors on adult Odonata (Insecta) from preserved and altered streams in the Amazonian region. Adult Odonata were sampled in 98 streams in the Eastern Amazon, Pará, Brazil. Six variables were used to measure local environmental factors: habitat integrity index; mean canopy over the channel; and four physical and chemical descriptors of the water. To measure regional environmental factors, six variables were also used: altitude gradient, three bioclimatic variables and two percentage forest variables. In partial redundancy analysis, both abiotic factors (local and regional) were important to explain the variation in the Odonata community. The Odonata community can be influenced by regional and local factors. The relationship between Odonata and the local (e.g., integrity, canopy cover, and physical and chemical descriptors of the water) and regional (e.g., bioclimatic and forest cover variables) environmental variables recorded in this study has important implications for the use of these organisms to monitor small streams of the Eastern Amazon. The scale at which habitat is measured is an important issue in community structuring studies considering the rapid environmental changes. It is of great importance to consider the different scales in studies assessing community structure, once an adequate habitat must meet the ecological needs of all stages of the life of the Odonata. Full article
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Article
Characterization of a Vitellogenin Receptor in the Bumblebee, Bombus lantschouensis (Hymenoptera, Apidae)
Insects 2019, 10(12), 445; https://doi.org/10.3390/insects10120445 - 12 Dec 2019
Cited by 9 | Viewed by 1014
Abstract
The vitellogenin receptor (VgR) belongs to the low-density lipoprotein receptor (LDLR) family, responsible for mediating the endocytosis of vitellogenin (Vg) into the ovaries to promote ovarian growth and oviposition. Here, we cloned and measured VgR gene expression characteristics in the bumblebee Bombus lantschouensis [...] Read more.
The vitellogenin receptor (VgR) belongs to the low-density lipoprotein receptor (LDLR) family, responsible for mediating the endocytosis of vitellogenin (Vg) into the ovaries to promote ovarian growth and oviposition. Here, we cloned and measured VgR gene expression characteristics in the bumblebee Bombus lantschouensis. RNA interference was used to validate VgR function. The results showed that the full length of the BLVgR cDNA was 5519 bp, which included a 5280 bp open reading frame encoding 1759 amino acids (AAs). Sequence alignment revealed that the protein contained 12 LDLa, 5 EGF, 2 EGF-CA and 10 LY domains. Phylogenetic analysis showed that BLVgR and the VgR of Bombus terrestris clustered together and the tree of bumblebees (Bombus) appeared as one clade next to honeybees (Apis). Transcript expression analysis showed that BLVgR was expressed in all tested tissues and showed the highest abundance in the ovaries. BLVgR expression was present in all developmental stages. However, the expression level in larvae was extremely low. In addition, the expression of BLVgR was significantly upregulated after egg laying in both workers and queens. In new emerging workers injected with 5 µg of VgR dsRNA, the expression level of BLVgR was 4-fold lower than that in the GFP dsRNA-injected group after 72 h. Furthermore, BLVgR silencing significantly reduced the number of eggs laid (3.67 ± 1.96 eggs) and delayed the first egg-laying time (16.31 ± 2.07 days) in worker microcolonies when compared to dsGFP (37.31 ± 4.09 eggs, 8.15 ± 0.22 days) and DEPC-treated water injected controls (16.42 ± 2.24 eggs, 10.00 ± 0.37 days). In conclusion, the BLVgR gene and its reproductive function were explored in the bumblebee B. lantschouensis. This gene plays an important role in egg laying time and egg number. Full article
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Article
Do Grapholita funebrana Infestation Rely on Specific Plum Fruit Features?
Insects 2019, 10(12), 444; https://doi.org/10.3390/insects10120444 - 11 Dec 2019
Cited by 3 | Viewed by 1399
Abstract
The effective control of the plum fruit moth, Grapholita funebrana (Lepidoptera: Tortricidae) still represents a difficult challenge for organic plum farming. Little information is available on the susceptibility of plum cultivars to this moth pest. We investigated the roles of several fruit parameters [...] Read more.
The effective control of the plum fruit moth, Grapholita funebrana (Lepidoptera: Tortricidae) still represents a difficult challenge for organic plum farming. Little information is available on the susceptibility of plum cultivars to this moth pest. We investigated the roles of several fruit parameters (i.e., shape, volume, hardness, fruit colour, and physiochemical properties) on the susceptibility of four different plum cultivars (Angeleno, Friar, President and Stanley) to G. funebrana attack. Field data demonstrated the importance of some fruit parameters (i.e., elongation index, sugar degree, titratable acidity, cover colour percentage) on susceptibility to G. funebrana infestation. Under laboratory conditions, colour and shape had a significant role in determining the time spent on false fruits, i.e., female moths preferred yellow and rounded fruits over elongated red or green fruits. Angeleno (yellow and rounded fruits) and Stanley (green and elongated fruits) were the most and least susceptible cultivars, respectively. Overall, this study adds useful knowledge about plum cultivar susceptibility to G. funebrana. Information reported here may be useful to improve integrated pest management strategies both in conventional and organic orchards because the use of less susceptible cultivars may reduce insecticidal treatments, limiting the development of resistance in target insects and the harmful side effects on beneficial species. Full article
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Article
Establishment in an Introduced Range: Dispersal Capacity and Winter Survival of Trissolcus japonicus, an Adventive Egg Parasitoid
Insects 2019, 10(12), 443; https://doi.org/10.3390/insects10120443 - 11 Dec 2019
Cited by 13 | Viewed by 1468
Abstract
The herbivorous brown marmorated stink bug, Halyomorpha halys, has spread globally, and one of its key parasitoids, Trissolcus japonicus, has recently been detected in the pest’s introduced range. For an exotic natural enemy to impact its targeted host in a novel [...] Read more.
The herbivorous brown marmorated stink bug, Halyomorpha halys, has spread globally, and one of its key parasitoids, Trissolcus japonicus, has recently been detected in the pest’s introduced range. For an exotic natural enemy to impact its targeted host in a novel environment, it must disperse, locate hosts, and potentially be redistributed to susceptible sites. Through intentionally releasing T. japonicus across four Oregon eco-regions, we investigated an introduced parasitoid’s dispersal capacity in urban sites and in two perennial crops, hazelnut and raspberry. In a second paired field and laboratory study, we investigated T. japonicus survival in different plant materials. Within three days of release, adult T. japonicus located host egg masses at 45% of sites and, one year later, were detected at 40% of release sites. Areas where released wasps survived winter were mostly urban or semi-natural. In commercial crop release experiments, we recovered the highest percentage of wasps in raspberry within 5 m of the release site but found no statistical difference in dispersal distance with some wasps dispersing up to 50 m. Adult parasitoids survived up to 16 weeks outdoors in the winter, with greater survival over time in bark compared to leaf litter. Wasp survival remained above 50% over the course of a simulated winter environment without precipitation. Our work affirms the continuation of H. halys parasitism by T. japonicus in novel environments and provides insight into the high population sizes necessary to survive winter and locate host egg masses the following season. Full article
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Article
Characterization of Dendrolimus houi Lajonquiere (Lepidoptera: Lasiocampidae) Transcriptome across All Life Stages
Insects 2019, 10(12), 442; https://doi.org/10.3390/insects10120442 - 09 Dec 2019
Cited by 8 | Viewed by 1278
Abstract
Dendrolimus houi Lajonquiere is a phytophagous caterpillar infesting many economically important coniferous tree species in China, causing serious economic and ecological environment losses. Based on previous research, it has one generation per year in South China and East China in contrast to two [...] Read more.
Dendrolimus houi Lajonquiere is a phytophagous caterpillar infesting many economically important coniferous tree species in China, causing serious economic and ecological environment losses. Based on previous research, it has one generation per year in South China and East China in contrast to two generations per year in Yunnan province in southwestern China. The species is potentially resilient to climatic extremes in these regions with the eggs and 1st instar larvae surviving in the winter (5 °C), older instar larvae and pupae surviving high temperatures in the summer (35 °C), suggesting some temperature stress tolerance during different developmental stages. However, little is known in this species at the genetic and genomic level. In this study, we used high throughput sequencing to obtain transcriptome data from different developmental stages (eggs, 1st–3rd instar larvae, 4th–5th instar larvae, 6th–7th instar larvae, pupae, male and female adults), which were collected from Fujian province. In total, we obtained approximately 90 Gb of data, from which 33,720 unigenes were assembled and 17,797 unigenes were annotated. We furtherly analyzed the differentially expressed genes (DGEs) across all stages, the largest number between the eggs and 1st instar larvae stage and gene expression varied significantly in different developmental stages. Furthermore, 4138 SSR genes and 114,977 SNP loci were screened from transcriptome data. This paper will be a foundation for further study towards improved integrated pest management strategies for this species. Full article
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Review
Bacterial Semiochemicals and Transkingdom Interactions with Insects and Plants
Insects 2019, 10(12), 441; https://doi.org/10.3390/insects10120441 - 08 Dec 2019
Cited by 7 | Viewed by 3267
Abstract
A peculiar feature of all living beings is their capability to communicate. With the discovery of the quorum sensing phenomenon in bioluminescent bacteria in the late 1960s, it became clear that intraspecies and interspecies communications and social behaviors also occur in simple microorganisms [...] Read more.
A peculiar feature of all living beings is their capability to communicate. With the discovery of the quorum sensing phenomenon in bioluminescent bacteria in the late 1960s, it became clear that intraspecies and interspecies communications and social behaviors also occur in simple microorganisms such as bacteria. However, at that time, it was difficult to imagine how such small organisms—invisible to the naked eye—could influence the behavior and wellbeing of the larger, more complex and visible organisms they colonize. Now that we know this information, the challenge is to identify the myriad of bacterial chemical signals and communication networks that regulate the life of what can be defined, in a whole, as a meta-organism. In this review, we described the transkingdom crosstalk between bacteria, insects, and plants from an ecological perspective, providing some paradigmatic examples. Second, we reviewed what is known about the genetic and biochemical bases of the bacterial chemical communication with other organisms and how explore the semiochemical potential of a bacterium can be explored. Finally, we illustrated how bacterial semiochemicals managing the transkingdom communication may be exploited from a biotechnological point of view. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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Article
Interspecific Competition between the House Fly, Musca domestica L. (Diptera: Muscidae) and Black Soldier Fly, Hermetia illucens (L.) (Diptera: Stratiomyidae) When Reared on Poultry Manure
Insects 2019, 10(12), 440; https://doi.org/10.3390/insects10120440 - 07 Dec 2019
Cited by 10 | Viewed by 2523
Abstract
Few studies have examined the competitive interaction between the house fly (HF) and the black soldier fly (BSF). The fact that the BSF deters HF oviposition is widely cited in BSF literature, but this interaction has not been assessed in over three decades. [...] Read more.
Few studies have examined the competitive interaction between the house fly (HF) and the black soldier fly (BSF). The fact that the BSF deters HF oviposition is widely cited in BSF literature, but this interaction has not been assessed in over three decades. In this study, the competitive interaction of BSF and HF larvae was observed on fresh (day 0) and aged poultry manure (manure aged for two, four, six, or eight days). Specifically, a priority effect study was conducted to determine if colonization sequence influences time to first pupariation (HF) or pre-pupation (BSF), survivorship, and weight. Results show >70% of HFs reached pupariation in all treatments except when placed on manure eight days after the initial inoculation with BSF. However, age of the resource negatively impacted time to first pupariation and puparium weight when HFs were reared alone or introduced two to eight days after BSF. No BSF pre-pupae resulted from treatments in which HFs were the pioneering species. BSFs reached the highest percent pre-pupation when reared alone on fresh manure, but BSFs may be more susceptible to the negative impacts of an aging resource, as no pre-pupae were observed when provided with six- or eight-day-old manure. Similar to HFs, age of the resource may have impacted development and survivorship; other factors such as moisture content, chemical composition, and amount of resource provided may have also impacted our results. These data may be useful in implementing BSFs as biological control agents of the HF, as well provide valuable information for facilities mass-producing HFs or BSFs for food or feed. Full article
(This article belongs to the Special Issue Control of House Flies and Stable Flies)
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Review
A Review of Interactions between Insect Biological Control Agents and Semiochemicals
Insects 2019, 10(12), 439; https://doi.org/10.3390/insects10120439 - 05 Dec 2019
Cited by 15 | Viewed by 3023
Abstract
Biological control agents and semiochemicals have become essential parts of the integrated pest management of insect pests over recent years, as the incorporation of semiochemicals with natural enemies and entomopathogenic microbials has gained significance. The potential of insect pheromones to attract natural enemies [...] Read more.
Biological control agents and semiochemicals have become essential parts of the integrated pest management of insect pests over recent years, as the incorporation of semiochemicals with natural enemies and entomopathogenic microbials has gained significance. The potential of insect pheromones to attract natural enemies has mainly been established under laboratory conditions, while semiochemicals from plants have been used to attract and retain natural enemies in field conditions using strategies such as trap crops and the push–pull mechanism. The best-known semiochemicals are those used for parasitoids–insect pest–plant host systems. Semiochemicals can also aid in the successful dispersal of entomopathogenic microbials. The use of semiochemicals to disseminate microbial pathogens is still at the initial stage, especially for bacterial and viral entomopathogens. Future studies should focus on the integration of semiochemicals into management strategies for insects, for which several semiochemical compounds have already been studied. More effective formulations of microbial agents, such as granular formulations of entomopathogenic fungi (EPFs), along with bio-degradable trap materials, could improve this strategy. Furthermore, more studies to evaluate species-specific tactics may be needed, especially where more than one key pest is present. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
Communication
Stag Beetle Elytra: Localized Shape Retention and Puncture/Wear Resistance
Insects 2019, 10(12), 438; https://doi.org/10.3390/insects10120438 - 05 Dec 2019
Viewed by 1762
Abstract
Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical [...] Read more.
Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical forces. In this study, stag beetle (Lucanus cervus) elytra were first examined for their overall flexural properties and were observed to have a localized shape-retaining snap-through mechanism, which may play a possible role in partly absorbing impact energy, e.g., during battles and falls from heights. The snap-through mechanism was validated using theoretical calculations and also finite element simulations. Elytra were also characterized to examine their puncture and wear resistance. Our results show that elytra have a puncture resistance that is much higher than that of mandible bites. The measured values of modulus and hardness of elytra exocuticle were 10.3 ± 0.8 GPa and 0.7 ± 0.1 GPa, respectively. Using the hardness-to-modulus ratio as an indicator of wear resistance, the estimated value was observed to be in the range of wear-resistant biological material such as blood worms (Glyrcera dibranchiata). Thus, our study demonstrates different mechanical properties of the stag beetle elytra, which can be explored to design shape-retaining bio-inspired composites with enhanced puncture and wear resistance. Full article
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Article
Oviposition-Induced Volatiles Affect Electrophysiological and Behavioral Responses of Egg Parasitoids
Insects 2019, 10(12), 437; https://doi.org/10.3390/insects10120437 - 05 Dec 2019
Cited by 10 | Viewed by 1254
Abstract
In response to an attack by herbivores, plants emit a variety of compounds that may act as semiochemicals. Oviposition-induced volatiles (OIPVs) have been shown to mediate interactions between plants and natural enemies. Here, we investigated the role of OIPVs by Tuta absoluta towards [...] Read more.
In response to an attack by herbivores, plants emit a variety of compounds that may act as semiochemicals. Oviposition-induced volatiles (OIPVs) have been shown to mediate interactions between plants and natural enemies. Here, we investigated the role of OIPVs by Tuta absoluta towards two egg parasitoids, Trichogramma cordubense and T. achaeae. We collected headspace volatiles from tomato plants at 24, 48, and 72 h after oviposition by T. absoluta females and tested the antennographic response of Trichogramma parasitoids to them by means of gas chromatography- electro-antennographical detection (GC-EAD). The response of the parasitoids was also tested in behavioral experiments using a Y-tube olfactometer. Oviposition by T. absoluta females induced qualitative and quantitative changes in the volatiles emitted by tomato plants. Antennae of Trichogramma parasitoids responded to several of the induced volatiles in GC-EAD. T. cordubense females were attracted to tomato plants with T. absoluta eggs 24 h after oviposition. The elucidation of the behavior of egg parasitoids towards OIPVs enhances the development of sustainable management strategies either by selecting species that exploit OIPVs or by manipulating their foraging behavior by utilizing specific OIPVs that are used by parasitoids as a host location. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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Article
The Association between Virus Prevalence and Intercolonial Aggression Levels in the Yellow Crazy Ant, Anoplolepis Gracilipes (Jerdon)
Insects 2019, 10(12), 436; https://doi.org/10.3390/insects10120436 - 04 Dec 2019
Cited by 5 | Viewed by 1539
Abstract
The recent discovery of multiple viruses in ants, along with the widespread infection of their hosts across geographic ranges, provides an excellent opportunity to test whether viral prevalence in the field is associated with the complexity of social interactions in the ant population. [...] Read more.
The recent discovery of multiple viruses in ants, along with the widespread infection of their hosts across geographic ranges, provides an excellent opportunity to test whether viral prevalence in the field is associated with the complexity of social interactions in the ant population. In this study, we examined whether the association exists between the field prevalence of a virus and the intercolonial aggression of its ant host, using the yellow crazy ant (Anoplolepis gracilipes) and its natural viral pathogen (TR44839 virus) as a model system. We delimitated the colony boundary and composition of A. gracilipes in a total of 12 study sites in Japan (Okinawa), Taiwan, and Malaysia (Penang), through intercolonial aggression assay. The spatial distribution and prevalence level of the virus was then mapped for each site. The virus occurred at a high prevalence in the surveyed colonies of Okinawa and Taiwan (100% infection rate across all sites), whereas virus prevalence was variable (30%–100%) or none (0%) at the sites in Penang. Coincidentally, colonies in Okinawa and Taiwan displayed a weak intercolonial boundary, as aggression between colonies is generally low or moderate. Contrastingly, sites in Penang were found to harbor a high proportion of mutually aggressive colonies, a pattern potentially indicative of complex colony composition. Our statistical analyses further confirmed the observed correlation, implying that intercolonial interactions likely contribute as one of the effective facilitators of/barriers to virus prevalence in the field population of this ant species. Full article
(This article belongs to the Collection Biology of Social Insect Diseases)
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Article
Leaf Morphological and Biochemical Responses of Three Potato (Solanum tuberosum L.) Cultivars to Drought Stress and Aphid (Myzus persicae Sulzer) Infestation
Insects 2019, 10(12), 435; https://doi.org/10.3390/insects10120435 - 04 Dec 2019
Cited by 9 | Viewed by 1104
Abstract
Drought stress on plants can cause cellular water deficits and influence the physiology of host plants, which alter the performance of insect pests. This study was conducted to determine the effect of drought and aphid (Myzus persicae Sulzer) infestation on three potato [...] Read more.
Drought stress on plants can cause cellular water deficits and influence the physiology of host plants, which alter the performance of insect pests. This study was conducted to determine the effect of drought and aphid (Myzus persicae Sulzer) infestation on three potato (Solanum tuberosum L.) genotypes under greenhouse conditions. A factorial experiment involving three potato genotypes, two levels of drought, and two levels of aphid infestation was conducted. The potato genotypes possessed different levels of tolerance to drought and are described as tolerant (Qingshu 9), moderately tolerant (Longshu 3), and sensitive (Atlantic). Sixty-day-old potato plants were infested with aphid nymphs and monitored for 20 d. There was a significant variety × drought × aphid interaction effect on the parameters measured. The genotype Atlantic, which is sensitive to drought, exhibited greater tolerance to aphid infestation under drought or no drought conditions than the other genotypes. This genotype also exhibited poor host acceptance and the aphid survival rate, colonization success, and average daily reproduction were low. Qingshu 9, which is tolerant to drought, was highly susceptible to aphid infestation and exhibited high host acceptance and greater aphid survival rate, colonization success, and average daily reproduction compared to the other genotypes. This study demonstrates that the biochemical and morphological traits that confer drought tolerance in potato do not necessarily confer aphid tolerance. Full article
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Article
Physalis peruviana L. (Solanaceae) Is Not a Host of Ceratitis capitata (Diptera: Tephritidae): Evidence from Multi-Year Field and Laboratory Studies in Colombia
Insects 2019, 10(12), 434; https://doi.org/10.3390/insects10120434 - 04 Dec 2019
Viewed by 1669
Abstract
Scientifically-based, tephritid fly host status determination lies at the heart of strategic regulatory decisions impinging on international fruit trade. Here we conducted intensive field and laboratory studies with peaches as controls, to determine the host status of Physalis peruviana for the Medfly—Ceratitis [...] Read more.
Scientifically-based, tephritid fly host status determination lies at the heart of strategic regulatory decisions impinging on international fruit trade. Here we conducted intensive field and laboratory studies with peaches as controls, to determine the host status of Physalis peruviana for the Medfly—Ceratitis capitata, as this fruit is experiencing a consumption boom worldwide. A total of 98,132 Uchuvas (local name), collected in Colombia from the plant or the ground over a three-year period (2016–2018) did not yield a single C. capitata larva or pupa, thus reaching a Probit 9 level with 99.9968% efficacy and 96% confidence level. Field-cage studies with enclosed fruit-bearing Uchuva plants, exposing fruit with an intact, damaged or totally removed husk to the attack of C. capitata, also failed to yield infestations. Highly artificial choice experiments, exposing gravid females to unripe and fully ripe fruit, resulted in an absence of infestations, even when overripe Uchuvas were artificially damaged. The husk and surface resins/waxes inhibit fly landings on fruit and oviposition activity. Considering our results and the fact that the foliage, husk and fruit of P. peruviana are repellent/toxic to insects, we conclude that this plant should be treated as a non-natural and non-conditional host of C. capitata. Full article
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Article
Trapping Brown Marmorated Stink Bugs: “The Nazgȗl” Lure and Kill Nets
Insects 2019, 10(12), 433; https://doi.org/10.3390/insects10120433 - 30 Nov 2019
Cited by 2 | Viewed by 3033
Abstract
Improvements to current brown marmorated stink bug (BMSB), Halyomorpha halys, surveillance and killing systems are needed to improve detection sensitivity and to reduce pesticide use. Detection of BMSB in New Zealand with traps is reliant on sticky panels with aggregation pheromone, which [...] Read more.
Improvements to current brown marmorated stink bug (BMSB), Halyomorpha halys, surveillance and killing systems are needed to improve detection sensitivity and to reduce pesticide use. Detection of BMSB in New Zealand with traps is reliant on sticky panels with aggregation pheromone, which are low cost but inefficient compared with beating foliage. Trapping for BMSB adults and nymphs was conducted daily with lethal traps consisting of an aggregation pheromone-baited-coat hanger covered with dark-colored long-lasting insecticide-treated mesh, we termed “The Nazgȗl”, based on its sinister appearance. A deep tray lined with white plastic was attached centrally at the base for collecting the dead BMSB. The lethal traps killed and caught up to 3.5-fold more nymphs and adult BMSB than identically-baited sticky panels in the 3 weeks of deployment, and provided a snapshot of phenology by instar. We expect that lure-and-kill stations could contribute to the suppression of a delimited population and could be included as part of a semiochemical-based eradication program. Attracting and killing females and nymphs, thus removing future offspring, could contribute to population suppression during an eradication. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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Article
Effects of Variety and Grape Berry Condition of Vitis vinifera on Preference Behavior and Performance of Drosophila suzukii
Insects 2019, 10(12), 432; https://doi.org/10.3390/insects10120432 - 30 Nov 2019
Cited by 6 | Viewed by 1280
Abstract
Drosophila suzukii is an invasive fruit pest and represents a potential economic threat to viticulture. After first observations of D. suzukii in Europe in 2008, research mainly focused on the evaluation of the host range and infestation risk for fruit and berry crops. [...] Read more.
Drosophila suzukii is an invasive fruit pest and represents a potential economic threat to viticulture. After first observations of D. suzukii in Europe in 2008, research mainly focused on the evaluation of the host range and infestation risk for fruit and berry crops. However, the risk assessment of D. suzukii in viticulture has only recently started. Understanding the factors influencing preferences of D. suzukii for host species and varieties as well as offspring performance is essential to improve management strategies. We investigated the field infestation of different grape varieties across Baden-Wuerttemberg, southwestern Germany, between 2015 and 2018. Moreover, we performed dual-choice assays in the laboratory to investigate whether adults show preferences for certain varieties and whether offspring performance differs between varieties. Furthermore, we studied the impact of grape damage on choice behavior. Field monitoring revealed that D. suzukii show preferences for red varieties, whereas almost no oviposition occurred in white varieties. The results of dual-choice assays confirmed that D. suzukii preference and performance are influenced by grape variety and that flies preferred damaged over intact “Pinot Noir”, “Pinot Blanc”, and “Müller-Thurgau” berries. Overall, these findings may have important implications for winegrowers regarding cultivated varieties, grape health, and insecticide reduction. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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Article
Behavioral Responses of the Invasive Fly Philornis downsi to Stimuli from Bacteria and Yeast in the Laboratory and the Field in the Galapagos Islands
Insects 2019, 10(12), 431; https://doi.org/10.3390/insects10120431 - 28 Nov 2019
Cited by 1 | Viewed by 1235
Abstract
Philornis downsi Dodge and Aitken (Diptera: Muscidae) is an avian parasitic fly that has invaded the Galapagos archipelago and exerts an onerous burden on populations of endemic land birds. As part of an ongoing effort to develop tools for the integrated management of [...] Read more.
Philornis downsi Dodge and Aitken (Diptera: Muscidae) is an avian parasitic fly that has invaded the Galapagos archipelago and exerts an onerous burden on populations of endemic land birds. As part of an ongoing effort to develop tools for the integrated management of this fly, our objective was to determine its long- and short-range responses to bacterial and fungal cues associated with adult P. downsi. We hypothesized that the bacterial and fungal communities would elicit attraction at distance through volatiles, and appetitive responses upon contact. Accordingly, we amplified bacteria from guts of adult field-caught flies and from bird feces, and yeasts from fermenting papaya juice (a known attractant of P. downsi), on selective growth media, and assayed the response of flies to these microbes or their exudates. In the field, we baited traps with bacteria or yeast and monitored adult fly attraction. In the laboratory, we used the proboscis extension response (PER) to determine the sensitivity of males and females to tarsal contact with bacteria or yeast. Long range trapping efforts yielded two female flies over 112 trap-nights (attracted by bacteria from bird feces and from the gut of adult flies). In the laboratory, tarsal contact with stimuli from gut bacteria elicited significantly more responses than did yeast stimuli. We discuss the significance of these findings in context with other studies in the field and identify targets for future work. Full article
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Article
Potential Pathways and Genes Involved in Lac Synthesis and Secretion in Kerria chinensis (Hemiptera: Kerriidae) Based on Transcriptomic Analyses
Insects 2019, 10(12), 430; https://doi.org/10.3390/insects10120430 - 28 Nov 2019
Cited by 3 | Viewed by 897
Abstract
Lac is a type of natural resin secreted by lac insects and is widely used in the military and other industries because of its excellent adhesion and insulation properties. The main ingredients of lac are lactones and lactides, which are formed from hydroxy [...] Read more.
Lac is a type of natural resin secreted by lac insects and is widely used in the military and other industries because of its excellent adhesion and insulation properties. The main ingredients of lac are lactones and lactides, which are formed from hydroxy fatty acids and sesquiterpene esters. In this study, we measured lac secretion rates by the insect Kerria chinensis at different developmental stages and identified lac secretion-minimum and lac secretion-active stages of the insect. We then analyzed transcriptomes of lac secretion-minimum and lac secretion-active stages of the insect. Based on expression profiles of genes in different stages of the insect, we identified pathways and genes that are potentially involved in lac synthesis and secretion in K. chinensis. Our study lays a foundation for future studies to reveal the molecular mechanisms and pathways of lac synthesis and secretion in this beneficial insect. Full article
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Article
The Complete Mitochondrial Genome of Bactrocera carambolae (Diptera: Tephritidae): Genome Description and Phylogenetic Implications
Insects 2019, 10(12), 429; https://doi.org/10.3390/insects10120429 - 28 Nov 2019
Cited by 4 | Viewed by 1179
Abstract
Bactrocera carambolae is one of the approximately 100 sibling species of the Bactrocera dorsalis complex and considered to be very closely related to B. dorsalis. Due to their high morphological similarity and overlapping distribution, as well as to their economic impact and [...] Read more.
Bactrocera carambolae is one of the approximately 100 sibling species of the Bactrocera dorsalis complex and considered to be very closely related to B. dorsalis. Due to their high morphological similarity and overlapping distribution, as well as to their economic impact and quarantine status, the development of reliable markers for species delimitation between the two taxa is of great importance. Here we present the complete mitochondrial genome of B. carambolae sourced from its native range in Malaysia and its invaded territory in Suriname. The mitogenome of B. carambolae presents the typical organization of an insect mitochondrion. Comparisons of the analyzed B. carambolae sequences to all available complete mitochondrial sequences of B. dorsalis revealed several species-specific polymorphic sites. Phylogenetic analysis based on Bactrocera mitogenomes supports that B. carambolae is a differentiated taxon though closely related to B. dorsalis. The present complete mitochondrial sequences of B. carambolae could be used, in the frame of Integrative Taxonomy, for species discrimination and resolution of the phylogenetic relationships within this taxonomically challenging complex, which would facilitate the application of species-specific population suppression strategies, such as the sterile insect technique. Full article
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Article
A Glycoproteinaceous Secretion in the Seminal Vesicles of the Termite Coptotermes gestroi (Isoptera: Rhinotermitidae)
Insects 2019, 10(12), 428; https://doi.org/10.3390/insects10120428 - 26 Nov 2019
Cited by 1 | Viewed by 1094
Abstract
Coptotermes gestroi is a subterranean termite with colonies generally headed by a pair of primary reproductives, although neotenics may occur. In this study, the male reproductive system was compared during different life stages of nymphs, alates, neotenic reproductives, and kings of C. gestroi [...] Read more.
Coptotermes gestroi is a subterranean termite with colonies generally headed by a pair of primary reproductives, although neotenics may occur. In this study, the male reproductive system was compared during different life stages of nymphs, alates, neotenic reproductives, and kings of C. gestroi, focusing on the modifications of this system along the maturation of these individuals. The structure of the male reproductive system follows the pattern described for insects, although C. gestroi males do not exhibit conspicuous penises and differentiated accessory glands. In kings, each testis consisted of about seven lobes, significantly increased in size as compared to younger males. The spermatogenesis begins in third-instar nymphs, which already presented spermatozoa in the testes. The seminal vesicles are individualized in C. gestroi and have a secretory distal portion and a proximal portion with a role in spermatozoa storage. The secretion of the seminal vesicles is strongly periodic acid Schiff (PAS)-positive, whereas the xylidine Ponceau test revealed proteins that increase in quantity while the males become older. This is the first record of glycoproteins in the lumen of seminal vesicles in termites. Further studies will clarify how they are produced and interact in the physiology and nutrition of the non-flagellate spermatozoa of C. gestroi. Full article
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Article
Life on the Edge: Ecological Genetics of a High Arctic Insect Species and Its Circumpolar Counterpart
Insects 2019, 10(12), 427; https://doi.org/10.3390/insects10120427 - 26 Nov 2019
Cited by 4 | Viewed by 1092
Abstract
Arctic ecosystems are subjected to strong environmental constraints that prevent both the colonization and development of many organisms. In Svalbard, few aphid species have established permanent populations. These high arctic aphid species have developed peculiar life-history traits such as shortened life cycles and [...] Read more.
Arctic ecosystems are subjected to strong environmental constraints that prevent both the colonization and development of many organisms. In Svalbard, few aphid species have established permanent populations. These high arctic aphid species have developed peculiar life-history traits such as shortened life cycles and reduced dispersal capacities. Here, we present data on the distribution and population genetics of Acyrthosiphon svalbardicum in Spitsbergen, the main island of the Svalbard archipelago, and compared its genetic structure with that of its close relative Acyrthosiphon brevicorne, sampled in the top of Scandinavian mainland. We found that A. svalbardicum is common but heterogeneously distributed along the west coast of Spitsbergen. We recorded this species up to 79°12’, which constitutes the northernmost location for any aphid. Genetic structure examined using microsatellite markers showed more pronounced spatial differentiation in A. svalbardicum than in A. brevicorne populations, presumably due to reduced dispersal capacities in the former species. Although populations of A. brevicorne and A. svalbardicum were well-delineated at nuclear loci, they shared similar cytoplasmic DNA haplotypes as revealed by sequence analysis of two DNA barcodes. These results raise questions about whether these two taxa are different species, and the colonization sources and history of the Svalbard archipelago by A. svalbardicum. Full article
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Article
Seasonal Assessment of Supercooling Points for Two Introduced and One Native Laricobius spp. (Coleoptera: Derodontidae), Predators of Adelgidae
Insects 2019, 10(12), 426; https://doi.org/10.3390/insects10120426 - 26 Nov 2019
Viewed by 776
Abstract
The hemlock woolly adelgid, Adelges tsugae Annand, is an invasive insect that threatens hemlock species in eastern North America. Several species from the genus Laricobius are predators of A. tsugae in its native areas of Asia and the western United States. Two Laricobius [...] Read more.
The hemlock woolly adelgid, Adelges tsugae Annand, is an invasive insect that threatens hemlock species in eastern North America. Several species from the genus Laricobius are predators of A. tsugae in its native areas of Asia and the western United States. Two Laricobius species have been released as biological control agents: Laricobius nigrinus Fender, and Laricobius osakensis Montgomery and Shiyake. Laricobius rubidus LeConte is an adelgid predator native to the Eastern United States, where it can feed and complete development on A. tsugae opportunistically. Laboratory assays were conducted to assess the cold hardiness of these three Laricobius species, including two distinct populations of L. osakensis, by measuring the supercooling points of each species from November 2016 through March 2017. This information may be useful for choosing the best-suited biological control agent for a particular region to control A. tsugae. There was a significant difference between the overall mean supercooling point of L. rubidus compared to the other Laricobius spp. There were also significant differences of supercooling points between L. rubidus and both strains of L. osakensis in January, and significant differences between L. rubidus and all other strains in February. L. rubidus appear better adapted to cold extremes in the eastern U.S. than imported Laricobius spp. Full article
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Article
Compatibility and Efficacy of the Parasitoid Eretmocerus hayati and the Entomopathogenic Fungus Cordyceps javanica for Biological Control of Whitefly Bemisia tabaci
Insects 2019, 10(12), 425; https://doi.org/10.3390/insects10120425 - 25 Nov 2019
Cited by 9 | Viewed by 1292
Abstract
Biological control is an effective method for whitefly management compared to the potential problems caused by chemical control, including environmental pollution and the development of resistance. Combined use of insect parasitoids and entomopathogenic fungi has shown high efficiency in Bemisia tabaci control. Here, [...] Read more.
Biological control is an effective method for whitefly management compared to the potential problems caused by chemical control, including environmental pollution and the development of resistance. Combined use of insect parasitoids and entomopathogenic fungi has shown high efficiency in Bemisia tabaci control. Here, we assessed the impacts of an entomopathogenic fungus, Cordyceps javanica, on the parasitism rate of a dominant whitefly parasitoid, Eretmocerus hayati, and for the first time also compared their separate and combined potential in the suppression of B. tabaci under semi-field conditions. Six conidial concentrations of C. javanica (1 × 103, 1 × 104, 1 × 105, 1 × 106, 1 × 107 and 1 × 108 conidia/mL) were used to assess its pathogenicity to the pupae and adults of E. hayati. Results showed that the mortality of E. hayati increased with higher concentrations of C. javanica, but these higher concentrations of fungus had low pathogenicity to both the E. hayati pupae (2.00–28.00% mortality) and adults (2.67–34.00% mortality) relative to their pathogenicity to B. tabaci nymphs (33.33–92.68%). Bioassay results indicated that C. javanica was harmless (LC50 = 3.91 × 1010) and slightly harmful (LC50 = 5.56 × 109) to the pupae and adults of E. hayati respectively on the basis of IOBC criteria, and that E. hayati could parasitize all nymphal instars of B. tabaci that were pretreated with C. javanica, with its rate of parasitism being highest on second-instar nymphs (62.03%). Interestingly, the parasitoids from second and third-instar B. tabaci nymphs infected with C. javanica had progeny with increased longevity and developmental periods. Moreover, experimental data from 15 day semi-field studies indicate that combined application of C. javanica and E. hayati suppresses B. tabaci with higher efficiency than individual applications of both agents. Therefore, combined applications of C. javanica (1 × 108 conidia/mL) and E. hayati is a more effective and compatible biological control strategy for management of B. tabaci than using either of them individually. Full article
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