Behaviour of Anopheles albimanus in relation to pyrethroid-treated bednets

Abstract. Responses of the malaria vector Anopheles albimanus to pyrethroid impregnated bednets made of cotton or nylon, compared with untreated nets, were investigated in houses occupied by two people inside and/or outside two bednets, in coastal Chiapas, México. The pyrethroid used was lambdacyhalothrin 30mga.i./m². Bioassay mortality rates of An.albimanus exposed to treated nets for 3 or 15min, rose from 40–55% to 90–100% for nylon nets 3–19 weeks post-treatment, but were consistently lower for treated cotton nets. An.albimanus females (collected unfed on human bait) were released in houses surrounded by curtains for trapping mosquitoes that exited from the house. Floor sheets were used in and around each experimental house for retrieving any mosquitoes knocked-down and/or killed. During post-treatment assessment for 17 weeks, An.albimanus blood-feeding success rates were 23–24% with untreated nets, 14–18% with treated cotton nets and 8–15% with treated nylon nets, significantly reduced when both human baits were inside the treated bednets, but not when one or more baits were outside the treated bednet(s) within the house. Proportions of mosquitoes leaving houses <3 h post-release were 53–59% from houses with untreated bednets versus 65–78% with treated bednets. Except in one case (when both humans were outside treated cotton nets), these increased early exit rates were significant, whether or not the human baits were inside the treated bednets indoors. Mortality rates of An.albimanus females exiting overnight (22.00–06.00 hours) averaged 15–39% from houses with treated cotton and 16–46% with treated nylon nets, very significantly greater than the control mean rates of 6–8% mortality with untreated nets. Observations on wild-caught An. albimanus females marked with fluorescent powder and released indoors revealed that few mosquitoes (3–11 %) actually contacted the bednets unless both human baits remained under them - when contact rates were 22% on treated nylon, 23% on treated cotton and 42% on untreated nets (P= 0.05). The mean resting time was significantly longer on untreated (14.4min) than on treated nylon (5.8min) or cotton (9.5 min) bednets, whereas mean resting times on other surfaces indoors were 16.5–19.8min. Proportions exiting within 2h of release were significantly more from houses with treated houses (33–35%) than with untreated nets (8%). However, mortality rates of mosquitoes that landed on treated nets were very significantly greater (90–100%) than after landing on untreated nets (10%). Thus, despite some excito-repellency, lambdacyhalothrin-impregnated bednets (especially made of nylon) proved to be effective as an alternative to house-spraying against An.albimanus.     

Bait-fed adult Culex pipiens carry the larvicide Bacillus sphaericus to the larval habitat

Sugar meals of plant origin are a basic component of mosquito diet. We show that sugar baits have potential as vehicles for control agents. When Culex pipiens L. resting-sites were sprayed with sucrose solution, with or without incorporation of the larval toxicant Bacillus sphaericus Neide, 47% of female mosquitoes fed in situ. Dispersing B. sphaericus-carrier mosquitoes caused larval mortality in breeding-sites 60-100 m from the sprayed resting-sites. The effect was not seen where no adults rested in sparse vegetation above larval habitats. This approach may be useful for the application of biological control agents against mosquitoes in biotopes where the adults and larvae are juxtaposed.     

Evaluation of boric acid as toxic sugar bait against resistant Aedes aegypti mosquitoes

Current methods of broad area application of contact insecticides used in mosquito control are becoming less effective, primarily due to resistance within mosquito populations. New methods that can deliver ingestible insecticides are being investigated as a means to mitigate resistance. This study evaluated insecticide delivery through toxic sugar baits (TSB) and resulting mortality of susceptible and resistant strains of Aedes aegypti. Two Ae. aegypti strains were evaluated using a 1% boric acid TSB: the susceptible Orlando 1952 (ORL) strain and the resistant Puerto Rican (PR) strain. The TSB resulted in high mortality for both ORL and PR strain of Ae. aegypti. Average mortality of female mosquitoes given TSB was 90.8% for PR and 99.3% for ORL. Our study suggests that targeting resistant mosquitoes with ingestible insecticides through TSBs could be a viable alternative to current mosquito control strategies and should be considered when developing an integrated vector management program.     

Indoor Application of Attractive Toxic Sugar Bait (ATSB) in Combination with Mosquito Nets for Control of Pyrethroid-Resistant Mosquitoes

Background

Attractive toxic sugar bait (ATSB) sprayed onto vegetation has been successful in controlling Anopheles mosquitoes outdoors. Indoor application of ATSB has yet to be explored. The purpose of this study was to determine whether ATSB stations positioned indoors have the potential to kill host-seeking mosquitoes and constitute a new approach to control of mosquito-borne diseases.

Methods

Insecticides were mixed with dyed sugar solution and tested as toxic baits against Anopheles arabiensis, An. Gambiae s.s. and Culex quinquefasciatus in feeding bioassay tests to identify suitable attractant-insecticide combinations. The most promising ATSB candidates were then trialed in experimental huts in Moshi, Tanzania. ATSB stations were hung in huts next to untreated mosquito nets occupied by human volunteers. The proportions of mosquitoes killed in huts with ATSB treatments relative to huts with non-insecticide control treatments huts were recorded, noting evidence of dye in mosquito abdomens.

Results

In feeding bioassays, chlorfenapyr 0.5% v/v, boric acid 2% w/v, and tolfenpyrad 1% v/v, mixed in a guava juice-based bait, each killed more than 90% of pyrethroid-susceptible An. Gambiae s.s. and pyrethroid-resistant An. arabiensis and Cx. quinquefasciatus. In the hut trial, mortality rates of the three ATSB treatments ranged from 41-48% against An. arabiensis and 36-43% against Cx. quinquefasciatus and all were significantly greater than the control mortalities: 18% for An. arabiensis, 7% for Cx. quinquefasciatus (p<0.05). Mortality rates with ATSB were comparable to those with long lasting insecticidal nets previously tested against the same species in this area.

Conclusions

Indoor ATSB shows promise as a supplement to mosquito nets for controlling mosquitoes. Indoor ATSB constitute a novel application method for insecticide classes that act as stomach poisons and have not hitherto been exploited for mosquito control. Combined with LLIN, indoor use of ATSB has the potential to serve as a strategy for managing insecticide resistance.     

广东城镇地区防治蚊虫试验

本文以20%除虫脲(即灭幼脲Ⅰ号)胶悬剂在广东省番禺县大岗镇地区进行防治蚊幼虫试验.结果表明,根据蚊种及其孽生地类型可施用0.1—1.0ppm的浓度,对白纹伊蚊、致倦库蚊和骚扰阿蚊幼虫都有比较好的效果,而且持效也比较长.经过每15—20天喷洒一次,防治面积共564m²,基本上控制了蚊虫的发生数量.通过诱蚊箱的监测,7—9月份处理区各月份的成蚊密度均比对照区低.在使用剂量的范围内,除虫脲对鲩鱼、鳙鱼、食蚊鱼和蝌蚪安全.其杀虫作用是抑制幼虫的生长发育和变态.     

The Impact of Hydrological Restoration on Benthic Aquatic Invertebrate Communities in a New Zealand Wetland

Drainage is a major disturbance affecting wetlands, as drains lower water tables and convert lentic habitats to lotic ones. Consequently, invertebrate communities in drained wetlands are likely to differ from those in unimpacted wetlands. This study investigated the effect of hydrological restoration on invertebrate communities in small drains in a New Zealand fen. Invertebrates were collected over 4 summers from 10 drains within the wetland, one of which was blocked as part of a restoration program. The sampling protocol thus represented a Before‐After Control‐Impact experiment. Invertebrate community composition varied over the 4 years, but variability was greatest in the manipulated drain before and after it was blocked. Relative abundance of the amphipod Paraleptamphopus decreased after blockage, whereas those of the midges Chironomus zelandicus and Tanypodinae increased. Relative abundances of these taxa in control sites were unchanged. Hydraulic restoration thus had a demonstrable impact on the invertebrate communities. The invertebrate community of the blocked drain was compared to that of natural wetlands in undisturbed catchments. Similarity was very low prior to drain blockage, but increased following drain blockage. Invertebrate communities in the restored drain were more similar to those of low pH wetlands than high pH wetlands. Given the goal of restoring the communities to those similar to natural conditions, this was a beneficial result. These results, coupled with studies that showed a decline in the cover of alien pasture grasses around the blocked drain, suggest that drain blockage represents a cost‐effective way of restoring wetland plant and aquatic invertebrate communities, especially where connectivity allows for the natural recruitment of these organisms into restored areas.     

Susceptibility of adult mosquitoes to insecticides in aqueous sucrose baits

Mosquitoes characteristically feed on plant‐derived carbohydrates and honeydew just after emergence and intermittently during their lives. Development of toxic baits focusing on this carbohydrate‐seeking behavior may potentially contribute to localized control. In the present study, ten insecticides were fed to female Culex quinquefasciatus, Anopheles quadrimaculatus, and Aedes taeniorhynchus in a 10% sucrose solution. Active ingredients representative of five classes of insecticides (pyrethroids, phenylpyroles, pyrroles, neonicotinoids, and macrocyclic lactones) were selected for comparison with commercial formulations used to facilitate incorporation of active ingredients into aqueous sucrose solutions. Sucrose as a phagostimulant significantly enhanced mortality to toxicants. In general, the most effective active ingredients were fipronil, deltamethrin and imidacloprid, followed by spinosad, thiamethoxam, bifenthrin, permethrin, and cyfluthrin. The least effective ingredients were chlorfenapyr and ivermectin. For some of the ingredients tested, Cx. quinquefasciatus was the least susceptible species. One‐day‐old male Cx. quinquefasciatus were more susceptible than females; however, no differences existed between one‐ and seven‐day‐old mosquitoes. There were no differences in susceptibility between unfed and gravid ten‐day‐old female Cx. quinquefasciatus to bifenthrin. In conclusion, several pesticides from different classes of compounds have potential for use in development of toxic baits for mosquitoes.     

Response of blanket bog vegetation to drain‐blocking

Question: Does blocking of moorland drains increase bog vegetation on blanket peat? Location: Two sites with blocked drains and two with unblocked drains on Forsinard Flows National Nature Reserve, Sutherland, UK. Methods: Vegetation cover was recorded from 70 locations, with 12 sampling points at different distances (0.5‐14.5 m) from moorland drains in each location. Gradients in the cover of species indicative of wet and dry conditions, as well as bog recovery and degradation in relation to distance from drain, were compared from a sample of drains at two sites with blocked drains and two with unblocked drains. Results: There was evidence for drain‐blocking having a negative effect on vegetation indicative of drier conditions and bog degradation. One of the blocked sites had the lowest values of these indices near to the drain and increasing at greater distances perpendicular from the drain. The two unblocked sites, and the other blocked site, had a contrasting pattern of highest values of these indices close to the drain declining with distance. Cover of species indicative of bog recovery was greater where the drains had been blocked for the longest time. Conclusions: In some cases drain‐blocking can improve the ecological functioning of blanket bogs by increasing cover of healthy bog vegetation. Further studies into the causes of such variability in restoring vegetation through drain‐blocking are needed to aid targeting of peatland restoration projects to areas or methods most likely to be effective.     

成蚊糖餐行为及其在蚊虫防制中的应用

蚊虫作为重要的病媒生物,其大多数种类在成虫阶段需要取食糖餐,且对不同糖餐组分表现出不同偏好。同时,糖餐行为具有特定的时辰节律。野外条件下,不同成蚊对不同开花植物及其果实具有不同的偏好,不同糖餐植物对成蚊的存活率、寿命、繁殖力的影响各不相同。成蚊对糖餐的定位与植物挥发物有关,目前已有多种糖餐植物的活性挥发物被鉴定。含毒糖诱剂对多种成蚊具有良好的防治效果,人们已将其用于多种病媒生物的防治及蚊媒病毒的检测。利用糖餐植物挥发物研发出蚊虫引诱剂,在降低蚊媒疾病风险方面具有广阔的应用前景。本文对成蚊取食糖餐的习性、成蚊偏好的糖餐植物相关研究以及如何利用成蚊的糖餐行为来进行蚊虫防制等进行了综述。     

Contrasting influences of stormflow and baseflow pathways on nitrogen and phosphorus export from an urban watershed

Eutrophication of urban surface waters from excess nitrogen (N) and phosphorus (P) inputs remains a major issue in water quality management. Although much research has focused on understanding loading of nutrients from storm events, there has been little research to understand the contribution of baseflow, the water moving through storm drains between rainfall events. We investigated the relative contributions of baseflow versus stormflow for loading of water and nutrients (various forms of N and P) by the storm drain network in six urban sub-watersheds in St. Paul, MN, USA. Across sites, baseflow made substantial contributions to warm season (May–October) water yields (27–66 % across sites), total N yields (31–68 %), and total P yields (7–32 %). These results show that while P was predominantly delivered by stormflow, N loading was similar between baseflow and stormflow. We found that baseflow was dominated by groundwater inputs, likely caused by interception of shallow groundwater by storm drains, but also that variability in N and P among sites was related in part to the connectivity of the storm drains to upstream lakes and wetlands in some watersheds. The substantial loading by groundwater-dominated baseflow, especially for N, implies that N management may require a broader focus on N source reduction, perhaps through improved land management, in order to prevent contamination of shallow groundwater via infiltration.     

Do colours that deter birds affect cereal bait acceptance by possums (

Poisonous baits used for pest control in New Zealand commonly contain green dye and cinnamon oil to make them less attractive to birds. Research aimed at reducing the impact of poison based pest control on birds has shown that some birds are initially deterred from feeding on blue or, to a lesser extent, green coloured food and are attracted to yellow or red food. We determined whether colours that deter or attract birds affected the acceptance of non-toxic and toxic cereal baits by captive brushtail possums (Trichosurus vulpecula). Individual possums were offered, daily, a choice between a standard green dyed non-toxic cereal bait and either a blue dyed(17 possums) or yellow dyed non-toxic bait (16 possums) for 10 days. Following this, for the first group of 17 possums, 1080 toxin was added to either the green bait (9 possums) or blue bait (8 possums) and possums were offered the green versus blue choice again. Two additional groups that had not previously been fed cereal baits were also given a choice between blue and green baits, one of which was toxic. All possums offered non-toxic bait ate less on the first day of presentation than on subsequent days. There was no difference in acceptance of either blue or yellow coloured non-toxic bait compared to the standard green non- toxic bait on any days. Bait colour appeared to be unimportant in cereal bait choice and did not deter possums from eating any of the baits. The addition of toxin to baits did not significantly alter bait choice in any groups, although some individuals which had no previous experience with baits ate more toxic than non-toxic bait. These data suggest that adding a stronger bird deterring colour (i.e., blue) to poisonous baits is unlikely to adversely affect the acceptance of baits by possums.     

红火蚁工蚁对颜色信号的选择与利用

为探明红火蚁Solenopsis invicta工蚁对颜色信号的选择与利用,本研究测定了不同颜色色卡对工蚁的趋向行为以及不同颜色饵料对工蚁觅食行为的影响,以期为红火蚁的高效监测与防控提供重要基础。结果表明颜色显著影响了红火蚁工蚁的趋向行为,黑色对工蚁的引诱率最高,可达32%;黄色对工蚁的引诱率最低,仅为7%。研究也发现不同颜色的饵料显著影响了红火蚁工蚁的觅食。在5 min时间内,工蚁在黄色、绿色以及蓝色饵料上觅食的数量最多,显著高于在紫色和黑色上饵料的觅食工蚁数;工蚁对红色、橙色、黄色、绿色、蓝色饵料的搬运量最大,显著高于紫色与黑色的饵料。综上,红火蚁工蚁可以识别与利用颜色信号,在制备红火蚁监测与防控饵剂时,可以考虑将饵剂染色红、橙、黄、绿、蓝等反射波长较长的颜色,以便工蚁能快速定位到饵剂并搬运更多的饵剂到蚁巢中。     

Sugar‐feeding behaviour and longevity of European Culicoides biting midges

Most haematophagous insect vectors can also use sugar as an energy source; thus their sugar‐feeding behaviour influences their longevity and blood‐feeding rate and hence their vectorial capacity. Scant information is available on the sugar‐feeding behaviour of Culicoides Latreille biting midges (Diptera: Ceratopogonidae), which are vectors of bluetongue and Schmallenberg viruses. The longevity of laboratory‐reared Culicoides nubeculosus (Meigen) under fluctuating temperatures (16 and 28 °C) and with access to water or water and blood was on average 6.4 days and 8.9 days, respectively, which was around one third of the lifespan of siblings with access to sugar or sugar and blood (22.2 days and 27.1 days, respectively). Access to honeydew significantly increased the midge's longevity, whereas the provision of extrafloral nectaries had no impact. Females with access to sugar produced a significantly higher number of eggs (65.5 ± 5.2) than their starved sisters (45.4 ± 8.4). More than 80% of field‐caught female Culicoides from the two most abundant European groups, Obsoletus (n = 2243) and Pulicaris (n = 805), were fructose‐positive. Fructose‐positivity was high in all physiological stages and no seasonal variability was noted. The high rate of natural sugar feeding of Culicoides offers opportunities for the development of novel control strategies using toxic sugar baits and for the monitoring of vector‐borne diseases using sugar‐treated FTA (nucleic acid preservation) cards in the field.     

Evaluation of a briquet formulation of Bacillus thuringiensis var. israelensis (H‐14) against aedes spp. and culex spp. larvae in dambos in Kenya

Bacillus thuringiensis Berliner var. israelensis serotype H‐14 (Bti) in briquet formulation (Bactimos) was tested in a field trial against ground‐pool breeding mosquitoes in a dambo located in a Rift Valley fever virus‐enzootic/epizootic area in central Kenya. Bactimos (10% Bti; 7000 AA International Toxic Units/mg) was tested for 30 days in 3 separate treatment areas at the rate of 1 briquet/9 m2, later increased to 1 briquet/1.5 m2 on day 13 postflood; 1 briquet/9 m2; and 1 briquet(4.6 m2). An estimate of the daily survival rate of larvae at different periods during the study revealed that mosquitoes in the area treated with 1 briquet/9 m2 had a significantly lower (64%) survival rate than those in the control site (92%) against Aedes spp. and was not significantly different from the site treated with 1 briquet/4.6 m². Mosquitoes in the site treated with I briquet/1.5 m² on day 13 postflood had a much‐reduced survival rate (25%;) when compared to those in the control site (67%) during the 3rd Culex spp. generation (22‐ 26 days postflood). This five‐fold increase above standard label dosage still failed to prevent Culex spp. emergence. There was no significant difference in survival rates between the control and any of the three treatment sites during the first or second Culex generation (9–20 days postflood). Emerged adults collected as pupae from control and treatment sites indicated that Aedes mcintoshi Huang and Culex antennatus (Becker) were the most predominant Aedes and Culex species.     

Sugar questing mosquitoes in arid areas gather on scarce blossoms that can be used for control

Floral nectar sugars provide energy for mosquito activities. We presumed that scarce flowering trees in arid areas are attractive, central sugar sources and tested the assumption in the southern desert of Israel. In traps baited with flowers of Acacia raddiana, Tamarix nilotica or Ochradenus baccatus the catch of Anopheles sergentii was approximately 35-75 times greater than with baits of flowerless branches. At a small isolated oasis, a spray of sugar and food-dye solution on the few flowering A. raddiana trees dye-labelled 80-90% of A. sergentii. At a similar oasis, this spray with addition of oral insecticide, virtually eliminated the local mosquitoes.     

Evaluation of the triflumuron and the mixture of Bacillus thuringiensis plus Bacillus sphaericus for control of the immature stages of Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) in catch basins

INTRODUCTION: In Cali, Colombia, catch basins (streetside storm drains) are one of the main larval habitats of Aedes aegypti and Culex quinquefasciatus. Since 1999, these mosquitoes have been controlled by the Secretaría de Salud Municipal (Secretary of Municipal Public Health) using the larvicide triflumuron. Because of high densities of these mosquitoes that remain in the city, treatment failure was suspected -possibly insecticide resistance of the target species. OBJECTIVES: The efficacy of triflumuron and VectoMax (biorational mixture of Bacillus thuringiensis var. israelensis plus Bacillus sphaericus) were evaluated in the control of A. aegypti and C. quinquefasciatus in catch basins. The residual effect of a single application of the biorational formulation was determined in catch basins during periods of high and low rainfall. MATERIALS AND METHODS: The efficacy of the products was measured in 60 catch basins located in a residential neighborhood of Cali for a period of 90 days. The mean number of immature instars (A. aegypti and C. quinquefasciatus larvae and pupae of both species) was determined biweekly from 40 catch basins with insecticide intervention (20 treated with triflumuron, 20 with VectoMax) and 20 untreated (control group). The residual effect of the biorational larvicide was evaluated biweekly in 10 catch basins during each of the 2 climatic periods. Results. The catch basins treated with VectoMax presented a significantly lower mean number of immature instars of both species compared with the control ( p<0.01). In contrast, the triflumuron treatment significantly reduced only immature instars of A. aegypti compared with the control ( p<0.001). The residual effect of VectoMax was higher during low rainfall compared to the control ( p<0.001). Conclusion. The biorational formulation was the more effective treatment for the control of both species during the period of evaluation (15 days).     

Control of Listeria spp. by competitive-exclusion bacteria in floor drains of a poultry processing plant

In previous studies workers determined that two lactic acid bacterium isolates, Lactococcus lactis subsp. lactis C-1-92 and Enterococcus durans 152 (competitive-exclusion bacteria [CE]), which were originally obtained from biofilms in floor drains, are bactericidal to Listeria monocytogenes or inhibit the growth of L. monocytogenes both in vitro and in biofilms at 4 to 37 degrees C. We evaluated the efficacy of these isolates for reducing Listeria spp. contamination of floor drains of a plant in which fresh poultry is processed. Baseline assays revealed that the mean numbers of Listeria sp. cells in floor drains sampled on six different dates (at approximately biweekly intervals) were 7.5 log(10) CFU/100 cm(2) for drain 8, 4.9 log(10) CFU/100 cm(2) for drain 3, 4.4 log(10) CFU/100 cm(2) for drain 2, 4.1 log(10) CFU/100 cm(2) for drain 4, 3.7 log(10) CFU/100 cm(2) for drain 1, and 3.6 log(10) CFU/100 cm(2) for drain 6. The drains were then treated with 10(7) CE/ml in an enzyme-foam-based cleaning agent four times in 1 week and twice a week for the following 3 weeks. In samples collected 1 week after CE treatments were applied Listeria sp. cells were not detectable (samples were negative as determined by selective enrichment culture) for drains 4 and 6 (reductions of 4.1 and 3.6 log(10) CFU/100 cm(2), respectively), and the mean numbers of Listeria sp. cells were 3.7 log(10) CFU/100 cm(2) for drain 8 (a reduction of 3.8 log(10) CFU/100 cm(2)), <1.7 log(10) CFU/100 cm(2) for drain 1 (detectable only by selective enrichment culture; a reduction of 3.3 log(10) CFU/100 cm(2)), and 2.6 log(10) CFU/100 cm(2) for drain 3 (a reduction of 2.3 log(10) CFU/100 cm(2)). However, the aerobic plate counts for samples collected from floor drains before, during, and after CE treatment remained approximately the same. The results indicate that application of the two CE can greatly reduce the number of Listeria sp. cells in floor drains at 3 to 26 degrees C in a facility in which fresh poultry is processed.     

Understanding the Long-Lasting Attraction of Malaria Mosquitoes to Odor Baits

The use of odor baits for surveillance and control of malaria mosquitoes requires robust dispensing tools. In this study, the residual activity of a synthetic mosquito attractant blend dispensed from nylon or low density polyethylene (LDPE) sachets was evaluated at weekly intervals for one year without re-impregnation. The potential role of bacteria in modulating the attraction of mosquitoes to odor-treated nylon that had been used repeatedly over the one year study period, without re-impregnation, was also investigated. Significantly higher proportions of female Anopheles gambiae sensu stricto mosquitoes were consistently attracted to treated nylon strips than the other treatments, up to one year post-treatment. Additional volatile organic compounds and various bacterial populations were found on the treated nylon strips after one year of repeated use. The most abundant bacteria were Bacillus thuringiensis and Acinetobacter baumannii. Autoclaving of treated nylon strips prior to exposure had no effect on trap collections of laboratory-reared female An. Gambiae (P = 0.17) or wild female An. Gambiae sensu lato (P = 0.26) and Mansonia spp. (P = 0.17) mosquitoes. Trap catches of wild female An. Funestus (P < 0.001) and other anophelines (P < 0.007) were higher when treated strips had been autoclaved prior to deployment as opposed to when the treated nylon strips were not autoclaved. By contrast, wild female Culex mosquitoes were more strongly attracted to non-autoclaved compared to autoclaved treated nylon strips (P < 0.042). This study demonstrates the feasibility of using odor baits for sampling and surveillance of malaria as well as other mosquito vectors over prolonged periods of time. Preliminary evidence points towards the potential role of bacteria in sustaining prolonged use of nylon material for dispensing synthetic attractant odorants for host-seeking malaria and other mosquito vectors but further investigations are required.     

Ants protect conifer seedlings from feeding damage by the pine weevil Hylobius abietis

• 1 Ants that protect food resources on plants may prey on (or deter) herbivores and thereby reduce damage. Red wood ants (of the Formica rufa group) are dominant ants in boreal forests of Eurasia and affect the local abundance of several herbivorous species.
• 2 The pine weevil Hylobius abietis (L.) is a herbivore that causes severe damage by feeding on the bark of coniferous seedlings within areas of forest regeneration.
• 3 We investigated whether ants can protect conifer seedlings from pine weevil feeding. In a manipulative experiment, ants were attracted to sugar baits attached to spruce seedlings and the damage caused by pine weevils was compared with control seedlings without ant‐baits.
• 4 The feeding‐scar area was approximately one‐third lower on the seedlings with ant‐baits compared with the controls. Besides red wood ants, Myrmica ants were also attracted in high numbers to the ant baits and the relative effects of these species are discussed.
• 5 The results obtained in the present study support the trophic cascade hypothesis (i.e. damage to herbivores is suppressed in the presence of predators). The decreased pine weevil feeding on the baited seedlings was probably a result of nonconsumptive interactions [i.e. the presence of (or harassment by) ants distracting pine weevils from feeding].
• 6 Understanding the role of ants may have important implications for future strategies aiming to control pine weevil damage. For example, maintaining suitable conditions for ants after harvesting stands may be an environmentally friendly but currently unexploited method of for decreasing weevil damage.

     

Source apportionment of non-storm water entries into storm drains using marker species: Modeling approach and verification

Inappropriate non-storm water entries into the storm drains and the resulting direct discharge into the natural environment on dry-weather days, is a challenging environmental issue in the cities worldwide. To make a preliminary evaluation of non-storm water entry situations, this study presented an approach for source apportionment of non-storm water entries into storm drains based on marker species and a chemical mass balance (CMB) model using a Monte Carlo statistical simulation. Compared with deterministic approaches, this method is capable of accounting for the measurement errors and the impact of variability of the source marker profiles resulting from heterogeneities and therefore presents the most likely range of estimated source contributions. This method was verified using measured data in a catchment in Shanghai, China, covering 374 ha. Here, inappropriate entries of sanitary wastewater, semiconductor wastewater, and groundwater into storm drains can be identified using acesulfame and citric acid, chloride, fluoride and sulfate, and total hardness, respectively, as markers. Using the measured marker profiles, the apportioned source flows were estimated with high precision in comparison to the investigated data, with a relative error less than 11%. Apportioned data revealed strong sanitary source connections to storm drains (i.e., 45.8% of the total sewage output), which were mainly from old residential communities with direct sewer connections to the storm pipes. Additionally, it revealed illicit semiconductor wastewater discharge contributed to 75% of the fluoride load, 52% of the sulfate load, and 32% of the chloride load, despite its low flow component of 9.2%. Therefore, a primary correction strategy of applying end-of-storm pipe control treatment, as well as reconnecting industrial source to the sewer network, was presented. Moreover, the marker library data associated with a variety of source types is expected to provide clear evidence for various non-storm water entry situations in future studies.