Insects are the most abundant animals on Earth, and the microbiota within their guts play important roles by engaging in beneficial and pathological interactions with these hosts. In this study, we ...comprehensively characterized insect-associated gut bacteria of 305 individuals belonging to 218 species in 21 taxonomic orders, using 454 pyrosequencing of 16S rRNA genes. In total, 174,374 sequence reads were obtained, identifying 9,301 bacterial operational taxonomic units (OTUs) at the 3% distance level from all samples, with an average of 84.3 (± 97.7) OTUs per sample. The insect gut microbiota were dominated by Proteobacteria (62.1% of the total reads, including 14.1% Wolbachia sequences) and Firmicutes (20.7%). Significant differences were found in the relative abundances of anaerobes in insects and were classified according to the criteria of host environmental habitat, diet, developmental stage, and phylogeny. Gut bacterial diversity was significantly higher in omnivorous insects than in stenophagous (carnivorous and herbivorous) insects. This insect-order-spanning investigation of the gut microbiota provides insights into the relationships between insects and their gut bacterial communities.
The repellent efficacy of 17 essential oils against the German cockroach, Blattella germanica was examined using a T-tube olfactometer. Five oils repelled B. germanica with good efficacy, ranging ...from 70.0 to 96.7%. Four of these oils, grapefruit, lemon, lime, and orange, were from the citrus family Rutaceae. These citrus essential oils showed similar repellent activity against two more cockroach species, such as Periplaneta americana and P. fuliginosa. Gas chromatography (GC) and GC-mass spectrometry analyses revealed that the major components responsible for the repellent activity of the citrus oils were limonene, beta-pinene and gamma-terpinene. Limonene appears to be the main component responsible for the repellent activity rather than beta-pinene and gamma-terpinene. The repellent efficacy of these components varied with different doses and the cockroach species tested. It is likely that minor components of the oils also contributed to the overall repellent activity of citrus essential oils, except orange oil. The activity of orange oil is almost solely attributed to the activity of limonene. Also, the repellent activity of citrus oil and that of each of the terpenoids makes little difference to the efficacy of a repellant against the three species of cockroaches.
The extremely halophilic archaeon Halobacterium noricense is a member of the genus Halobacterium. Strain CBA1132 (= KCCM 43183, JCM 31150) was isolated from solar salt. The genome of strain CBA1132 ...assembled with 4 contigs, including three rRNA genes, 44 tRNA genes, and 3,208 open reading frames. Strain CBA1132 had nine putative CRISPRs and the genome contained genes encoding metal resistance determinants: copper-translocating P-type ATPase (CtpA), arsenical pump-driving ATPase (ArsA), arsenate reductase (ArsC), and arsenical resistance operon repressor (ArsR). Strain CBA1132 was related to Halobacterium noricense, with 99.2% 16S rRNA gene sequence similarity. Based on the comparative genomic analysis, strain CBA1132 has distinctly evolved; moreover, essential genes related to nitrogen metabolism were only detected in the genome of strain CBA1132 among the reported genomes in the genus Halobacterium. This genome sequence of Halobacterium noricense CBA1132 may be of use in future molecular biological studies.
Whiteflies are sap-sucking insects belonging to the hemipteran order. They are well known for their menace to agriculture, as pests and vectors, and are reported for their bacterial and Rickettsia ...association in B biotype. In the present investigation, culture-dependent and -independent methods were used to reveal the bacterial phylotypes associated with B and Q biotypes. Cultivable bacterial phylotypes varied with respect to growth media and biotypes. Twenty different bacterial genera, including 31 species belong to Actinobacteria, 'alpha'-, 'beta'-, 'gamma'- Proteobacteria, and Firmicutes were isolated from both the biotypes. Of the seventeen phylotypes, Bacillus, Kocuria, Moraxellla, Micrococcus, Sphingomonas and Staphylococcus were common to both B and Q biotypes. Moreover, B biotype was associated with Acinetobacter, Deinococcus, Modestobacter, Microbacterium, and Pseudomonas, whereas Q biotype was associated with Arthrobacter, Bradyrhizobium, Janibacter, Morganella, Naxibacter, and Streptomyces. Application of a culture-independent method revealed the presence of additional symbiotic bacteria: Rickettsia in B biotype and Halomonas in Q biotype, as well as primary endosymbiont in both biotypes, which could not be obtained through culture-dependent method. Presence of Staphylococcus, Micrococcus (in both B and Q biotypes), and Bacillus (only in B biotype) in all developmental stages of B. tabaci indicated their close association with host insect.
The effect of electron beam irradiation on each developmental stage of diamondback moth,
Plutella xylostella L. (Lepidoptera: Plutellidae), was examined. Eggs, larvae, pupae, and adults were ...irradiated at target doses of 30, 50, or 100
Gy or they were left untreated as controls in replicated experiments. When eggs and pupae were irradiated with 100
Gy, emergence rates greatly decreased and, although some adults laid eggs, they did not hatch. Egg hatching of irradiated larvae and adult decreased with increasing irradiation doses. However, electron beam irradiation did not kill
P.
xylostella directly. Adult longevity was not affected. Reciprocal crosses between irradiated and unirradiated moths demonstrated that females were more radiosensitive than males in hatchability; however, the difference was not significant. In addition, electron beam-irradiated larvae showed typical DNA fragmentation in a dose-dependent manner compared with cells from unirradiated larvae. Our findings suggest that electron beam irradiation induces abnormal development and reproduction of
P.
xylostella; therefore, it may contribute to effective disinfestation and quarantine treatments of
P.
xylostella.
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This study was performed to investigate the repellent effect of 5
μl doses of ten essential oils (bergamot, chamomile, clary sage, fennel, lavender, lemongrass, majoram, peanut, pennyroyal, and ...peppermint) against
Lycorma delicatula 4th nymphs using an olfactometer. Only lavender oil exhibited significant repellency. We then tested 10, 5, 2.5, and 1
μl doses of lavender oil against the nymphs and females of
L. delicatula. The oil showed significant repellency at 10 and 5
μl, although the latter is less potent to 1st instar nymphs. At the lavender oil dose of 2.5
μl, only 3rd and 4th instar nymphs and females were significantly affected. None of the stages tested were affected by 1
μl. Chromatographic and mass spectrometric analyses of lavender oil detected linalool (42.2%), linalyl acetate (49.4%), terpinen-4-ol (5.0%), and caryophyllene oxide (3.4%). Among the four main components, only linalool showed repellency to all instar nymphs and females. No synergism was detected. Antennae of all instar nymphs and females showed electrophysiological responses only to linalool. In field studies using linalool, 4th nymphs and adults were highly repelled at a dose of 30
μl of lavender oil. The effect differed according to test plot and treatment dose.
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► Among ten tested essential oils,
L. delicatula was responded on the lavender oil using an olfactometer. ► Antennae of all instar nymphs and females showed electrophysiological responses only to linalool. ► The repellent effect of lavender oil was confirmed to the field. ► Treatment with 30
μl lavender oil showed significant repellent effect to the nymphs and females to the field.
Bistrifluron, a member of the benzoylphenylurea (BPU) class, was developed in the Republic of Korea as an inhibitor of chitin synthesis. This study examined the effect of bistrifluron on insecticidal ...activity, adult longevity, fecundity and ovarian development in the sycamore lace bug, Corythucha ciliata. The results showed that bistrifluron had no direct effect on the egg, but produced 100% mortality in larvae hatched within 24 hr with a similar effect regardless of the instars of the larvae (LCsub(50)=0.01-0.06 ppm). When the final instar was treated with bistrifluron, the emergence rate, adult longevity and reproduction decreased with increasing concentration (up to 100 ppm). With the passage of time after the final larvae had emerged, chemical treatment delayed the preoviposition period of the adults at high concentrations, and decreased adult longevity, fecundity and the hatching rate. Ovarian development of the adult was also inhibited.
Attraction responses of plant essential oils were investigated, and the electrophysiological response to nymphs and adults of spot clothing wax cicada (Lycorma delicatula) was confirmed. Of the ten ...tested oils, only spearmint oil was found attractive. In dose responses of spearmint oil, second to fourth instar nymphs, as well as adults, were significantly attracted to a dose of 5 μL; for nymphs, fourth instar nymph showed greatest attraction response (90.9%), and second and third instar nymphs showed mild attraction. At a dose of 10 μL, fourth instar nymphs and adults were significantly attracted to spearmint oil. Only fourth instar nymphs were attracted to spearmint oil at 2.5 μL. After analyzing spearmint oil using gas chromatography (GC) and GC/mass spectrometry, carvone constituent was found as a significant attractant for both nymphs and adults, except for first instar nymphs. Limonene did not show any attraction response. All constituents mixed with each other appeared to have an additive effect. In electrophysiological response to spearmint oil, antennae of only fourth instar nymphs and female adults responded to carvone. Therefore, spearmint oil may be effective as an attractant for control of L. delicatula populations. In a field test, fourth nymphs and female adults were highly attracted to 20 μL of spearmint oil. This is the first report on attraction response of L. delicatula to spearmint oil in the laboratory and the field.
The green peach aphid, Myzus persicae Sulzer, is an important sap-sucking pest of many plants, including Chinese cabbage. The objective of the present study was to determine the effects of sublethal ...concentrations of two insecticides (flonicamid and thiamethoxam) and the action mechanisms on the feeding behavior of M. persicae. The median lethal concentrations (LC∧50) of flonicamid and thiamethoxam for adult M. persicae were 2.56 and 4.02 mg/L, respectively. The sublethal concentrations of flonicamid were 0.44 mg/L (LC∧10) and 1.25 mg/L (LC∧30), and those of thiamethoxam were 1.19 mg/L (LC∧10) and 2.45 mg/L (LC∧30). The developmental period of M. persicae nymphs was 5.9 days at LC∧10 and 6.1 days at LC∧30 for both insecticides compared to 5.7 days for the control. Adult longevities at LC∧10 and LC∧30 of flonicamid were 13.2 and 13.7 days, respectively. Adult longevity at LC∧10 of thiamethoxam was 14.7 days. Control adult longevity was 11.6 days. Total fecundity was higher at LC∧10 (41.8 offspring/female) and LC∧30 (43.0 offspring/female) of flonicamid, and at LC∧10 (42.1 offspring/female) of thiamethoxam than that of the control (29.5 offspring/female). Feeding behavior analysis using an electrical penetration graph showed that sublethal doses of flonicamid and thiamethoxam had significant effects on the duration of phloem ingestion. However, higher doses of flonicamid induced starvation by inhibition of phloem ingestion and higher doses of thiamethoxam induced contact toxicity rather than inhibition of feeding behavior. This study provides the basis for a more efficient use of these pesticides in Korea.
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