[Application of Fe3[KG-*2/5]O4/Mulberry Stem Biochar Effects on Soil Arsenic Species and Rice Arsenic Content].

The passivation effect of Fe3O4/mulberry pole biochar (Fe-MBC) prepared at different carbonization temperatures on soil available arsenic content was studied through soil culture experiments, and Fe-MBC-800 (prepared by carbonization at 800℃) with good passivation effect was selected and characterized. The effects of 1%-7% (mass fraction of biochar to soil) Fe-MBC-800, MBC-800, and Fe3O4 on soil pH value, soil electrical conductivity, soil arsenic form, rice biomass, and total arsenic (As) content in rice were studied using a pot experiment. The results showed that:①Fe-MBC-800 successfully loaded Fe3O4, and its main functional groups were C=O double bond, O-H bond, C-O bond, and Fe-O bond. The specific surface areas of Fe-MBC-800, MBC-800, and Fe3O4 were 209.659 m2·g-1, 517.714 m2·g-1, and 68.025 m2·g-1, respectively. ②The addition of Fe-MBC-800 could increase the soil pH value, decrease the soil EC value, increase the content of residual arsenic in soil, and reduce the content of water-soluble arsenic and available arsenic in the soil. Under the treatment using 7% Fe-MBC-800 (ω) amendments, the content of water-soluble arsenic and available arsenic in the soil decreased by 81.6% and 56.33%, respectively. ③When the addition ratio of Fe-MBC-800 in the soil was 5%-7%, it could promote the growth of rice plants, increase rice biomass, and reduce the bioaccumulation of arsenic by between 62.5% and 68.75%.

Attraction of Culex pipiens pallens (Diptera: Culicidae) to Floret Volatiles and Synthetic Blends of Its Nectar Host Plant Abelia chinensis (Rubiales: Caprifoliaceae).

Abelia chinensis R. Br. (Dipsacales: Caprifoliaceae) is one of the preferred nectar host plants for Culex pipiens pallens Coquillett (Diptera: Culicidae). However, the volatile compounds of its flowers that might be involved in directing mosquitoes' orientation to its nectaries remain unknown. In the present study, the volatile compounds released by A. chinensis florets were collected by solid phase microextraction fiber and analyzed by gas chromatography-mass spectrometry system. Based on the major component species in the volatile profile, a synthetic phytochemical blend (Blend B, composed of six compounds at their most attractive concentrations) was formulated, and its attractiveness was tested against the pentane extract of A. chinensis florets at most attractive concentration (Blend A) and a formerly developed synthetic phytochemical blend (Blend C) in the olfactometer, respectively. The results revealed that the volatile profile of A. chinensis florets was mainly composed of aromatic compounds, most of which had been reported to be attractive to other mosquito species. The synthetic Blend B was as attractive as Blend A (10-1-fold of the crude pentane extract) in the olfactometer bioassays, but they were not as attractive as the formerly developed Blend C. The present study indicated that quantitative and qualitative differences in the constituents of phytochemical blends could significantly affect their attractiveness to Cx. pipiens pallens, and the capture efficiency of phytochemical attractants deserves further research before being applied in the field.

Feeding on different attractive flowering plants affects the energy reserves of Culex pipiens pallens adults.

Mosquito adults usually need to ingest sugar from nectar host plants to sustain their metabolic needs. Mosquitoes could be differentially attracted by various flowering plant species, and the volatiles were thought to be important factors attributed to the differential attractiveness. However, whether mosquitoes' preference for host plants correlates with their nutritional rewards from sugar sources remains unclear. In the present study, the preference of newly emerged Culex pipiens pallens to three kinds of flowering plants (Ligustrum quihoui, Abelia chinensis, and Nerium indicum) was determined in the olfactometer. Besides, when the newly emerged mosquitoes were provided with these flowering plants as sugar sources, the content of their metabolic reserves (glycogen, lipid, and protein) was determined. The results revealed that Cx. pipiens pallens could be differentially attracted by the odors emitted by the inflorescences of the tested flowering plants, and the nutritional rewards of mosquitoes were significantly affected by feeding on different inflorescences. The present study demonstrated that feeding on nectar host plants with differential attraction could affect the energy reserves of Cx. pipiens pallens.

Laboratory evaluation of differential attraction of Culex pipiens pallens to fruit-based sugar baits.

Mosquito adults usually need to obtain sugar from floral nectaries and damaged fruits/seed pods to replenish their energy reserves. The newly developed attractive toxic sugar baits have been successfully applied in controlling various mosquito species outdoors. However, the attraction of Culex pipiens pallens to different fruit-based sugar baits remains unknown. In the present study, we selected nine common fruit species, prepared the fruit-based sugar solutions, and investigated the attractiveness of different sugar baits to newly emerged Cx. pipiens pallens in the laboratory. The results showed that when tested against the 5% brown sugar solution, all the sugar baits were significantly attractive to both females and males. When tested together in the mesh-covered cage, there was a significant difference on the attractiveness between different fruit-based sugar baits. The most attractive fruit species included Broussonetia papyrifera, Cucumis melo, C. melo var. saccharinus, Amygdalus persica and Pyrus bretschneideri, and their seed pods could be potentially used as ingredients in ATSB for controlling mosquitoes outdoors.

Survivorship and fecundity of Culex pipiens pallens feeding on flowering plants and seed pods with differential preferences.

Adult mosquitoes rely on ingestion of sugar from plants to survive, swarm and mate. Culex pipiens pallens Coguillett is the primary vector of lymphatic filariasis and epidemic encephalitis. Little is known about the effect of feeding on different sugar sources on the survivorship and fecundity of Cx. pipiens pallens. In the present study, newly emerged mosquitoes were exposed to several flowering plant and seed pod species with different olfactory preferences, and the survival times of mosquitoes exposed to these sugar sources were determined. The proportions of mosquitoes that ingested sugar from host plants were investigated by cold anthrone tests. The numbers of eggs per egg raft laid by mosquitoes were compared when they were provided with different sugar sources and one blood meal. The results revealed that feeding on different kinds of sugar sources significantly affected female and male mosquitoes' survival times. Cold anthrone tests indicated that the proportions of sugar-positive mosquitoes from different nutritional regimes within 24h corresponded to the preference rankings of Cx. pipiens pallens to these sugar sources, and rapid declines in the proportions of surviving individuals might be attributed to their insufficient ingestion of sugar from nutritional regimes. Feeding on different sugar sources strongly affected the proportions of engorged mosquitoes, and females that had fed on their preferred sugar sources laid more eggs than mosquitoes provided with less preferred sugar sources. The results would provide insights in developing mosquito control strategies that target the sugar feeding behavior of mosquitoes.

Behavioural response of female Culex pipiens pallens to common host plant volatiles and synthetic blends.

BACKGROUND: Most mosquito species need to obtain sugar from host plants. Little is known about the chemical cues that Culex pipiens pallens use during their orientation to nectar host plants. In this study, we investigated the behavioural responses of female Cx. pipiens pallens to common floral scent compounds and their blends. METHODS: Behavioural responses of female Cx. pipiens pallens to 18 individual compounds at different concentrations were determined in the olfactometer bioassays. A synthetic blend composed of behaviourally active compounds was formulated, and its attractiveness to mosquitoes was tested. Several most attractive compounds constituted a reduced blend, and its attractiveness was tested against the solvent and the full blend, respectively. Mosquito response in the olfactometer was analyzed by comparing the percentages of mosquitoes caught in the two arms by χ(2) test (observed versus expected). RESULTS: Fifteen of the 18 compounds were attractive to female Cx. pipiens pallens in the dose-dependent bioassays, with the exception of ß-pinene, acetophenone and nonanal. (68.00 ± 2.49) % mosquitoes responded to the full blend composed of these 15 compounds on their optimal doses when tested against the solvent, with the preference index at 46.11 ± 3.57. Six individual compounds whose preference indices were over 40 constituted the reduced blend, and it attracted (68.00 ± 1.33) % mosquitoes when tested against the solvent while its preference index was 42.00 ± 3.54. When tested against the full blend simultaneously in the olfactometer, the reduced blend could attract (45.00 ± 2.69) % of released mosquitoes, which was as attractive as the full blend. CONCLUSIONS: Our results demonstrate that female Cx. pipiens pallens is differentially attracted by a variety of compounds at different concentrations. Alteration of the concentration strongly affects the attractiveness of the synthetic blend. Several floral scent volatiles might be the universal olfactory cues for various mosquito species to locate their nectar host plants, which could be potentially used in trapping devices for surveillance and control of them.