Mammals as source of ectoparasites in towns.

Four ecological groups of mammal ectoparasites are recognized in urban environment and their medical importance is briefly mentioned.     

温室条件下丽蚜小蜂的扩散行为

丽蚜小蜂Encarsia formosa是粉虱类害虫的重要寄生性天敌,目前已广泛应用于设施蔬菜烟粉虱Bemisia tabaci和温室白粉虱Trialeurodes vaporariorum的防控。本文在温室条件下对丽蚜小蜂的扩散行为进行了研究,并分析了扩散距离、释放时间等因素对其寄生率的影响。结果表明,丽蚜小蜂成虫释放后其扩散行为是渐进的、不连续的,主要在1~4 m范围内扩散,少量个体可扩散至6~8 m。番茄植株高度对丽蚜小蜂寄生率没有明显影响,这说明其释放后可成功地搜索到不同高度植株上的寄主。丽蚜小蜂释放后第2 d,距释放点l和2 m处其寄生率分别为92.5%和85.3%;释放后4 d,距释放点l和2 m处其寄生率分别为53.1%和39.7%。同一释放时间距释放点l和2 m处丽蚜小蜂寄生率没有显著差异,但却显著高于距释放点4、6和8 m处丽蚜小蜂的寄生率。因此,从寄生率也可以看出丽蚜小蜂成虫主要在1~4 m范围内进行扩散。利用丽蚜小蜂的有效扩散距离和寄生率可以确定其在温室的释放数量、释放点之间的距离和释放次数,研究结果对于更好地发挥丽蚜小蜂在生物防治中的控害作用具有重要的应用意义。     

Bait aggregation to reduce cost and toxin use in aerial 1080 baiting of small mammal pests in New Zealand

BACKGROUND: The metabolic toxin sodium fluoroacetate (‘compound 1080’) is widely used for controlling introduced mammalian pests in New Zealand. For large-scale operations, 1080 is distributed aerially in bait to kill brushtail possums (Trichosurus vulpecula Kerr) and ship rats (Rattus rattus L.). While usually successful in reducing pest populations by > 80%, widespread distribution of toxic bait is relatively expensive and raises concerns from some members of the public. Here, trials with spatial aggregation of baits in forested habitats were conducted to determine whether this can reduce toxin usage while maintaining operational efficacy. RESULTS: When 1080 baits were aggregated into clusters (by hand sowing) or into strips (by precision aerial deployment), indices of possum relative abundance were reduced by 92–100%, compared with 73–100% reductions using conventional aerial broadcasting, while all methods reduced relative abundance indices of rats by 88% or greater. Radio tracking indicated a kill rate of > 90% against possums, regardless of bait distribution method. CONCLUSIONS: Simply by modifying bait distribution patterns, spatial aggregation can be used to maintain the high encounter rate of pests with 1080 bait that is necessary for operational efficacy, while reducing current toxin usage by up to 80%. Aggregated bait delivery could have relevance for other mammalian pest control scenarios internationally. Copyright © 2012 Society of Chemical Industry     

Insect-Mediated Dispersal of the Rhizobacterium Pseudomonas chlororaphis

ABSTRACT The southern corn rootworm, Diabrotica undecimpunctata subsp. howardi, a common and mobile insect pest, was shown to transmit the rhizobacte-rium Pseudomonas chlororaphis strain L11 between corn plants. Strain L11 has been genetically modified to contain the lacZY genes from Escherichia coli. It can reach high densities on roots and invade the roots and move into the foliage. D. undecimpunctata subsp. howardi became infested with L11 as larvae while feeding on roots of seed-inoculated corn and retained the bacteria through pupation, molting to the adult stage, and emergence from the soil. Bacterial densities on or in the insects increased 100-fold after they fed again as adults on L11-infested foliage. Adults retained the bacteria for at least 2 weeks after last exposure and could transmit L11 to new plants. The likelihood of transmission decreased with time since last exposure to L11, but increased with time spent on the new plants. This research demonstrates that rhizobacteria can escape the rhizosphere by moving in or onto foliage, where they can then be acquired and transmitted by insects. This transmission route may be common among naturally occurring rhizobacteria and facilitate the dispersal of both beneficial and harmful soilborne microorganisms.     

Dispersal of Synchytrium psophocarpi in Papua New Guinea

Airborne sporangia of Synchytrium psophocarpi showed a diurnal periodicity, maximum numbers occurring between 1600 and 1800 h and minimum numbers between 0600 and 0700 h. There wers significant correlations between the amounts of airborne sporangia and temperature (positive), relative humidity (negative) and dew (negative). The numbers of airborne sporangia increased following the onset of the wet season (November—April) but declined after the onset, of the dry season (May—October). Most airborne sporangia appeared to deposit within 15 m of their source. The potential for dispersal of sporangia by rain splash was demonstrated.     

外来广聚萤叶甲在我国的扩散及生活史特征

外来广聚萤叶甲目前已在我国华东的江苏、江西、安徽、浙江等省以及华中的湖北、湖南等省扩散蔓延；在野外其主要寄主是豚草，偶见取食苍耳。广聚萤叶甲在24、27、30℃恒温条件下完成一代分别为29．8、26．0和22．2d；野外完成1代需21～29d。在室外罩笼观察的4个世代中，前3个世代（6—8月）的各虫态历期及其存活率近似，产卵量接近；但9月初开始的第4个世代各虫态历期延长、存活率明显降低，产卵量（108．8粒）低于此前世代的一半。广聚萤叶甲的发育起点温度和有效积温分别为11．5℃和373．5日度；在南京推测广聚萤叶甲1年可发生5代。     

Dispersal of Spores of Fusarium culmorum in Aquatic Systems

ABSTRACT The dispersal of spores of Fusarium culmorum, a biological control agent for the aquatic weed Hydrilla verticillata, was investigated in aquatic systems. Macroconidia and chlamydospores that were applied to the surface of the liquid settled rapidly in deionized water, tap water, 5% Hoagland's solution, natural spring water, or river water held in glass containers. The rate of fall, as measured for 50% of the spores, was determined to be 9 cm h(-1). Rapid lateral dispersal of spores from a point source occurred in still water. This initial spore movement occurred at a rate of >9 m h(-1) (15 cm min(-1)), approximately 100 times faster than the rate of settlement. The spores attained an even lateral distribution in a still, closed system. Spores dispersed rapidly in moving water and were transported with the water current. Spores were determined to carry positive electrostatic charges as they migrated towards the negative pole during electrophoresis. The physical components of dispersal of F. culmorum spores were defined in a still aquatic system to consist of rapid lateral dispersal and sinking due to gravity. In moving water, the dynamics of water movement was superimposed over the other two factors.     

Effect of Rain Distribution Alteration on Splash Dispersal of Colletotrichum acutatum

ABSTRACT Splash dispersal of Colletotrichum acutatum conidia from infected strawberry fruit was assessed using a rain simulator to determine the properties of rain (e.g., intensity [millimeters/hour] or drop size distribution) most related to dissemination. Dispersal with a simulated rain corresponding to a natural rain of about 11 mm/h was compared with dispersal of three other simulated rains that had larger and smaller drop sizes, on average, than idealized natural rains. Splash droplets were collected in sheltered petri plates with a selective medium for Colletotrichum, and colonies formed from conidia entrained in the droplets were counted and used as the measure of dispersal. Colonies were mostly confined to a 27-cm radius from the source, and density of colonies decreased exponentially with the distance squared, as indicated by the fit of a diffusion-type model to the data. Splash dispersal was more affected by drop size distribution than rain intensity or other properties of the generated rains. That is, there was a direct positive relationship between total colonies over 61 min of rain for a circular area with a 72-cm radius (Sigma) and the mass (volume) median diameter of impacting drops (D(0)') for four rain-simulation treatments. In a separate study, strawberry fruit were exposed to the same four simulated rains at two distances from a point source and for two rain durations. Although the proportion of infected fruit (y) increased with time and decreased with distance, rain treatment did not significantly affect y, as predicted based on past work with a wide range of intensities of simulated rains.     

芝麻花对稻螟赤眼蜂寄生和扩散能力的影响

芝麻是一种适合于稻田生态系统的蜜源植物,但其对稻田优势赤眼蜂稻螟赤眼蜂的作用未有系统的研究。本文在室内和大田的条件下考察了芝麻花对稻螟赤眼蜂寄生力和扩散能力的影响。室内结果表明,芝麻花可以显著的提高稻螟赤眼蜂对米蛾卵的寄生力。同时芝麻花显著影响了稻螟赤眼蜂的初始扩散能力,初始起飞蜂比例从71.4%下降至50.5%,但总的扩散蜂比例从91.9%增加至95.4%。田间结果显示田埂种植芝麻花可以提高稻螟赤眼蜂的寄生能力约30%,且更多的蜂扩散至距田埂20~25 m的距离。总之,芝麻花可显著的提高稻螟赤眼蜂寄生和扩散能力。     

低温贮藏对丽蚜小蜂生长发育和扩散的影响

丽蚜小蜂Encarsia formosa作为烟粉虱Bemisia tabaci和温室白粉虱Trialeurodes vaporariorum的重要寄生性天敌,目前已实现了规模化繁育,广泛应用于设施蔬菜粉虱类害虫的防控。该寄生蜂在大面积释放前往往要进行数量储备,因此低温贮藏是实现其规模化生产和应用的重要环节。本文在明确丽蚜小蜂蛹期最适贮藏发育阶段的基础上,研究了不同低温贮藏方式对丽蚜小蜂生长发育和适合度的影响,并在温室条件下明确了低温贮藏对其扩散和寄生的影响。结果表明,丽蚜小蜂的蛹在4℃和8℃下低温贮藏仍可继续发育,解剖低温贮藏后未羽化的丽蚜小蜂发现其死亡主要发生在蛹的发育初期和后期,蛹的发育中期死亡比例最低;贮藏前经历适度的低温诱导（12℃/7 d）可以显著提高丽蚜小蜂的羽化率、寄生量和成虫寿命（P<0.05）;温室条件下未经低温贮藏的丽蚜小蜂主要在1～4 m范围内扩散,而低温贮藏后羽化的丽蚜小蜂主要在1～2 m范围内扩散;适度的低温诱导（12℃/7 d）同样可以明显提高丽蚜小蜂在温室条件下的寄生率（P<0.05）。研究结果对于更好地发挥丽蚜小蜂在生物防治中的控害作用具有重要的应用意义。     

Investigations into carbamate insecticide selectivity: II: Differential degradation of selectophores in insect and mammal

Investigations were made of the effects of various modifications of the ether moiety alkoxyiminomethylphenyl N-methylcarbamates on the selective toxicity of the compounds to mouse vs. housefly. The highest mammalian selectivity ratio was found with o-(isopropyloxyiminomethyl)-phenyl N-methylcarbamate which was about 30-fold more toxic to fly than to mouse. The o-(1-propynyloxyiminomethyl)-phenyl N-methyl-carbamate was the most toxic compound to the housefly. The biochemcial basis for selective action was investigated.     

Dispersal of Ceratitis capitata Wied. on Procida Island 1)

A preliminary experiment, to relate the flight capability of Ceratitis to irradiation doses and to feeding, has shown that 9 Krads is a suitable dose for control programs and that feeding the newly emerged flies seems to affect their distribution over greater distances.     

A survey of annual pesticide usage during the control of sheep ectoparasites in Northern Ireland, 1997

This is the third survey of control practices for ectoparasites on sheep farms in Northern Ireland, providing data comparative to those recorded in previous surveys in 1981 and 1988. Data relating to all aspects of ectoparasite control were collected from 210 farms representing 4% of the total sheep population. Quantitative data have been adjusted to provide accurate estimates of total pesticide usage. Since the previous survey in 1988, the number of sheep farms in Northern Ireland has increased by 10% to 11 692 with a consequent 39% increase in sheep population to 2.9 million. Despite this level of expansion, the total quantity of organophosphorus compounds used for ectoparasite control has remained approximately constant at 7–8 tonnes. The report considers that compulsory sheep‐dipping, prescribed since 1970 and revoked in 1993, impacted significantly on subsequent ectoparasite control practices and consequent pesticide usage. During 1997, approximately 20% of sheep farmers relied on alternative methods to control ectoparasites, including injectable formulations of avermectins and pour‐on formulations of insect growth regulators and pyrethroids. Dipping formulations containing pyrethroid compounds, which accounted for <1% of treatments in 1988, increased to 9% in 1997. Previously, regulatory sheep‐dipping periods were specified during the autumn months, which tended to increase dipping frequency. The majority of farmers dipping sheep during the summer strictly for blowfly maggot (Diptera: Calliphoridae) control were required to perform additional compulsory sheep‐dipping during the autumn. Withdrawal of compulsory sheep‐dipping has allowed farmers to synchronise dipping practices to control the major ectoparasites of sheep at a single dipping occasion. An estimated 7.5 × 10⁶ litres of surplus dipwash required disposal and there were approximately equal numbers of farmers disposing dipwash immediately after sheep‐dipping or on occasions up to and including subsequent dipping. The decline in the number of farmers who allowed dipwash to run‐off into soakaways or surrounding soil observed in 1988 continued in 1997. The majority of farmers used tractor‐operated pumps to dispose of dipwash into slurry tanks for subsequent disposal onto permanent pasture. © Crown copyright 2000. Reproduced with the permission of Her Majesty's Stationery Office. Published for SCI by John Wiley & Sons, Ltd.     

Dispersal of Phytophthora nicotianae on tomatoes grown by nutrient film technique in a greenhouse

Tomatoes were grown in a greenhouse by nutrient film technique (NFT). They were inoculated withPhytophthora nicotianae either by direct inoculation of roots or by adding fungal spores to a container with recirculating nutrient solution. In the first case, the resulting epidemic seemed to be polycyclic, in the second case monocyclic. In both cases, inoculum freely circulated through the NFT system and was present in the nutrient solutions for at least 6 days after inoculation.Samenvatting Kastomaten werden gekweekt met behulp van voedingsfilmtechniek. Zij werden geinoculeerd metPhytophthora nicotianae hetzij door directe besmetting van wortels, hetzij door een sporensuspensie toe te voegen aan het voorraadvat met voedingsoplossing. In het eerste geval leek een polycyclische epidemie te volgen. In het tweede geval ontstond een monomcyclische epidemie. In beide gevallen werd schimmelinoculum door het gehele gotensysteem rondgepompt. Inoculum bleef gedurende tenminste 6 dagen na inoculatie aantoonbaar in de voedingsoplossing.     

Effects of a Cover Crop on Splash Dispersal of Colletotrichum acutatum Conidia

ABSTRACT A rain simulator, with generated rains of 11 and 30 mm/h, was used to determine the effect of a cover crop or intercrop on the splash dispersal of Colletotrichum acutatum conidia. Dispersal through sudangrass, which can be used as a 'living mulch', was tested at two planting densities (140 or 280 kg/ha) and two heights (5 and 20 cm) and compared with a control consisting of a bare soil. Dispersal of C. acutatum conidia was assessed by counting colonies formed from spore-bearing splash droplets deposited in sheltered petri plates containing a selective medium. Both a cover crop and rain intensity significantly affected splash dispersal as measured by the interpolated total number of colonies (denoted by Sigma) from 0 to 72 cm from the inoculum source and in a time span of 61 min of generated rain (P < 0.001). However, there was no significant interaction of cover crop and intensity (P > 0.90). Dispersal with a 30-mm/h rain was higher than dispersal with a 11-mm/h rain, and presence of a cover crop significantly reduced dispersal compared with bare soil (P < 0.001). Of the treatments with sudangrass, cover crop planting density did not affect dispersal overall, but there was greater spore dispersal with the taller sudangrass at the higher planting density, due in part to the higher rate of water splashing with the tall grass compared with the short grass. Spore deposition in the petri plates could be functionally related to distance and time using a diffusion-type model, and parameter estimates could be used to explain the effects of cover crop on Sigma. Although the relationship between cover crop properties and splash dispersal is complex, results show the potential beneficial effects of the cover crop on disease management.     

新疆特殊生境下微生物资源

概述了新疆大型真菌、新疆豆科植物根瘤菌、新疆陆生固氮蓝藻、新疆地衣、新疆极端环境微生物等5类微生物资源的研究进展和研究意义,同时指出了新疆微生物资源研究目前存在的两个重要盲区,即新疆非豆科植物共生固氮菌和新疆菌根真菌资源的研究,提出了这两个盲区研究的价值、意义、必要性和紧迫性。     

Effects of Single-Drop Impactions and Natural and Simulated Rains on the Dispersal of Botryosphaeria dothidea Conidia

ABSTRACT Laboratory and field experiments were conducted to study the dispersal of Botryosphaeria dothidea conidia using single-drop impactions and natural and simulated precipitations. For laboratory studies, 200 single drops were released from a height of 1 m on infected pistachio nuts. On pieces of photographic film, 50% of the droplets were collected within 20 mm (average droplet travel distance) of the target area, and the droplets ranged from 0.041 to 3.19 mm in diameter, with an average of 0.3 mm. Each droplet carried an average of 23 B. dothidea conidia. In 3 years of field experiments, rainwater was collected in funnels connected to bottles positioned at different heights inside the tree canopy and at different distances away from the edge of tree canopy in three commercial pistachio orchards in San Joaquin, Yolo, and Glenn counties in California. Numbers of conidia in rainwater varied among and within sampling seasons by sampling dates and orchards. Up to 67,000 conidia/ml were obtained in rainwater samples collected from an orchard in Yolo County. Rainwater from orchards in Yolo and Glenn counties contained a consistently higher number of conidia than rainwater collected from the orchard in San Joaquin County. Variation in numbers of conidia also existed among heights where bottles were located. There were significantly more conidia in rainwater collected inside than outside tree canopies. Inside tree canopies, bottles located at 100 and 150 cm above ground collected more B. dothidea conidia than those placed at 50 and 200 cm. Conidia were collected as far as 1 m from the tree canopy edge. Based on data from the Glenn County orchard, a linear relationship between number of conidia (Y) and rainfall amount (X) in millimeters was determined as Y = 240X - 3,867, with r(2) = 0.91, which meant that a minimum of 16.1 mm of rain was needed to disperse conidia of B. dothidea. The power law model best described the dispersal gradients of B. dothidea propagules in the 1999-2000 and 2001-02 sampling seasons, with r(2) values of >/=0.73, whereas the exponential law model fit best for the 2000-01 data, with r(2) values of >/=0.81. In a rain simulation experiment, the intensity of the rain generated by a nozzle at 138 kPa of pressure inside the tree canopy was approximately five times higher than rain recorded outside the tree canopy. Rain removed up to 65% of conidia from infected fruit. These results confirmed that B. dothidea is a splash-dispersed pathogen with relatively short distances of spore dispersal within pistachio orchards. Only pycnidia are present in pistachio orchards; therefore, the results also indicate that inoculum of B. dothidea should be entirely splashed dispersed.     

Rain Splash Dispersal of Gibberella zeae Within Wheat Canopies in Ohio

ABSTRACT Rain splash dispersal of Gibberella zeae, causal agent of Fusarium head blight of wheat, was investigated in field studies in Ohio between 2001 and 2003. Samplers placed at 0, 30, and 100 cm above the soil surface were used to collect rain splash in wheat fields with maize residue on the surface and fields with G. zeae-infested maize kernels. Rain splash was collected during separate rain episodes throughout the wheat-growing seasons. Aliquots of splashed rain were transferred to petri dishes containing Komada's selective medium, and G. zeae was identified based on colony and spore morphology. Dispersed spores were measured in CFU/ml. Intensity of splashed rain was highest at 100 cm and ranged from 0.2 to 10.2 mm h(-1), depending on incident rain intensity and sampler height. Spores were recovered from splash samples at all heights in both locations for all sampled rain events. Both macroconidia and ascospores were found based on microscopic examination of random samples of splashed rain. Spore density and spore flux density per rain episode ranged from 0.4 to 40.9 CFU cm(-2) and 0.4 to 84.8 CFU cm(-2) h(-1), respectively. Spore flux density was higher in fields with G. zeae-infested maize kernels than in fields with maize debris, and generally was higher at 0 and 30 cm than at 100 cm at both locations. However, on average, spore flux density was only 30% lower at 100 cm (height of wheat spikes) than at the other heights. The log of spore flux density was linearly related to the log of splashed rain intensity and the log of incident rain intensity. The regression slopes were not significantly affected by year, location, height, and their interactions, but the intercepts were significantly affected by both sampler height and location. Thus, our results show that spores of G. zeae were consistently splash dispersed to spike heights within wheat canopies, and splashed rain intensity and spore flux density could be predicted based on incident rain intensity in order to estimate inoculum dispersal within the wheat canopy.     

Environmental Factors Affecting the Release and Dispersal of Ascospores of Mycosphaerella citri

ABSTRACT Greasy spot, caused by Mycosphaerella citri, produces a leaf spot disease affecting all citrus species in Florida and the Caribbean Basin. M. citri produces pseudothecia and ascospores, which are considered the principal source of inoculum, in decomposing leaves on the grove floor. In studies using a computer-controlled environmental chamber, a single rain event triggered release of most mature ascospores beginning 30 to 60 min after the rain event. Additional rain events did not bring about further release. High relative humidity without rain triggered release of low numbers of ascospores, but vibration and red/infrared irradiation had little or no effect on ascospore release. After three to four cycles of wetting and drying of leaves, all pseudothecia had matured and released their ascospores. In the field, ascospores were detectable starting about 2 h after the beginning of a rain or irrigation and most ascospores were released within 16 h. Ascospore release was greatest following rain events and somewhat less following irrigations, and low numbers of ascospores were detectable on days without precipitation. Ascospore numbers declined linearly with horizontal distance from the source and as a function of the logarithm of ascospore numbers with vertical distance. Low numbers of ascospores were detected 7.5 m above the ground and 90 m downwind from the grove. Ascospore release can be advanced by irrigating frequently during dry, nonconducive conditions to stimulate ascospore release when environmental conditions are unfavorable for infection, but the eventual effects on disease severity are uncertain.