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1.
为了探究河套灌区在实施节水灌溉下的水盐平衡机制,在河套灌区永济灌域选择1个典型研究区,通过观测耕地和盐荒地土壤含水率及含盐量、地下水位埋深及矿化度,分析耕、荒地水盐动态规律及其主要影响因素,探讨盐荒地对耕地的"旱排"作用。结果表明:在灌溉和降雨的影响下,耕地土壤含水率比盐荒地土壤含水率变化更剧烈,耕地土壤含水率的主要影响因素是灌溉及降雨、作物生长、地下水位埋深和土壤质地,盐荒地土壤含水率的主要影响因素是耕地灌溉和地下水位埋深;耕地土壤含盐量在3.5 g·kg-1以下,为轻度盐碱化土壤,盐荒地土壤含盐量较高,其中心区域的土壤含盐量在4.0～10.0 g·kg-1,为重度盐碱化土壤,耕地土壤含盐量的主要影响因素是灌溉和作物生长,盐荒地土壤含盐量的主要影响因素是地形地貌和地下水位埋深;盐荒地地下水位埋深低于耕地地下水位埋深,耕地地下水矿化度在3.0 g·L-1以下,为微咸水,盐荒地中心区域地下水矿化度平均在8.5 g·L-1左右,为重度咸水。在无地表排水措施条件下,分布于耕地之间的盐荒地是耕地水盐的排泄区...  相似文献   

2.
地下水是我国西北干旱半干旱区的重要资源，而大规模的节水改造工程势必造成地下水环境的变化。本文从时空概率分布角度，探索了河套灌区永济灌域节水改造前（1998—2000年）、初期（2001—2006年）、中期（2007—2012年）和后期（2013—2018年）地下水埋深和地下水矿化度的时空变化特征，并运用指示Kriging法分析了节水改造前后不同阈值条件下地下水埋深和矿化度的空间概率分布规律。结果表明：（1）随着节水改造工程的推进，地下水埋深和矿化度均呈增加趋势，节水改造后期（2013—2018年）较节水改造前（1998—2000年）平均埋深增加了0.36 m，矿化度增加了1.37 g·L-1。（2）空间尺度上，节水改造后期33%的浅埋地下水（地下水埋深<2.0 m）高概率区（发生概率在0.5以上）过渡为深埋地下水的高概率区，且受城镇化影响（开采利用量大），中南部和北部地下水埋深增加显著；矿化度<2.5 g·L-1和≥3.0 g·L-1的高概率区分别扩大了17%和4%，即研究区中南部地下水趋于淡化，北部及东西边...  相似文献   

3.
本研究针对祁连山国家公园山体沿海拔(2700～4043 m)自下而上出现的针叶林、草甸化草原、高寒灌丛、高寒草甸、流石滩稀疏植被5种典型植被,研究土壤碳、氮、磷含量及生态化学计量比垂直分异规律,为祁连山国家公园生态系统土壤碳氮磷生物地球化学循环过程提供数据参考和科学依据。结果表明：(1)祁连山山体垂直带上0～40 cm土壤总碳、总氮和总磷含量分别为15.33～83.46 g·kg-1、1.63～7.76 g·kg-1、0.41～0.66 g·kg-1。土壤总碳和总氮含量均表现为针叶林>草甸化草原>高寒灌丛>高寒草甸>流石滩稀疏植被,都是沿着海拔的升高显著降低。土壤全磷含量表现为高寒灌丛显著高于高寒草甸,其余植被间差异不显著。(2)0～40 cm土壤铵态氮、硝态氮、速效磷含量分别为11.01～14.73 mg·kg-1、2.78～12.46 mg·kg-1和4.35～13.57 mg·kg-1。土壤铵态氮含量在各植被类型间差异不显著,...  相似文献   

4.
回嵘  谭会娟  黄磊  李新荣 《干旱区研究》2023,(11):1776-1784
为探讨柴达木盆地不同程度盐渍化土壤养分和酶活性特征，沿察尔汗盐湖至昆仑山方向依次选择5个样点，分析土壤养分和酶活性特征及其二者的相关性。结果表明：除土壤全钾外，土壤盐渍化程度、土壤深度及其两者交互作用对土壤养分含量及土壤酶活性的影响均达到显著水平(P<0.05)。在盐渍化程度较低的土壤，养分有效性(速效钾除外)和酶活性较高，且随土壤深度的增加而降低。以有机碳和蔗糖酶为例，在盐渍化程度最低的S5样地中含量为13.83 g·kg-1和21.01 mg·g-1·d-1(0～5 cm)、12.85 g·kg-1和19.29 mg·g-1·d-1(5～10 cm)、9.83 g·kg-1和12.19 mg·g-1·d-1(10～20 cm)，显著高于盐渍化程度最高S1中的8.56 g·kg-1和1.41 mg·g-1·d-1(0～...  相似文献   

5.
为揭示平原水库周边无灌溉盐荒地及防风林生长区水盐分布特征,在沙漠绿洲区多浪水库南库区周围布设了地下水监测井和土壤监测点,进行了为期2 a的逐月地下水埋深监测和土壤含水率及含盐量的定点取样测定试验。结果表明:库区周边盐荒地地下水埋深随监测时段变化变幅不大,2 a内均值为1.28 m;不同土壤含水率整体随土层深度增加呈升高趋势,其中60~100 cm的土壤含水率较其他土层波动较大。2 a间盐荒地的土壤含盐量在0.48~8.86 g·kg~(-1)之间变化,不同土壤总盐含量随土层深度增加呈减小的趋势,0~40 cm土层含盐量变化较为明显,具有显著的盐分表聚现象,其中,防风林地土壤含盐量在0~40 cm土层内较天然生态林地明显降低。  相似文献   

6.
冻融作用下地下水浅埋区土壤盐分及离子变化特征   总被引：1，自引：0，他引：1  
冻融作用是地下水浅埋区土壤盐渍化的重要原因之一，了解其对土壤盐分及离子变化的影响对土壤盐渍化防治具有重要意义。为探究冻融作用下土壤盐分及离子的分布及变化规律，以太谷均衡实验站地中蒸渗仪系统为试验设备，结合野外和室内试验分析了2020—2021年冻融期内6种不同地下水埋深下土壤剖面水分、可溶性盐分及离子含量的变化特征以及冻结层在冻融过程中对土壤盐分运移的影响，并采用灰色关联法分析了土壤含盐量与离子间的关联度。结果表明：（1）蒸渗仪土壤中以Na+、Ca2+、HCO3-、SO42-及Cl-为主，土壤含盐量与Na+和HCO3-极显著相关，与Ca2+、SO42-和Cl-显著相关。（2）冻结层在整个冻融过程中对于Ca2+和Cl-变化影响较小，对Na  相似文献   

7.
奇台县绿洲农田土壤盐渍化影响因素及逆向演替特征研究   总被引：2，自引：0，他引：2  
在奇台县绿洲中部平原区和绿洲沙漠交错带选择不同耕种时间的农田,分析其剖面土壤可溶性总盐、pH值含量随耕种时间的变化。探讨在地下水埋深不断下降的过程中,不同发展阶段农田土壤盐渍化的时空变化规律。研究表明:奇台县绿洲地下水埋深已低于影响地表盐渍化的地下水埋深临界值(5m),地下水矿化度低于3g/L,研究区整体处于有利于土壤盐渍化逆向演替的环境。土壤含盐量与地下水埋深关系最为密切,地下水埋深在3-5m时,土壤脱盐速度最快,大于5m时,含盐量减少的速率明显降低。土壤盐渍化逆向演替具有时空特征。时间特征表现在,无论农田在绿洲的什么位置,耕种时间越长,土壤含盐量越低,盐渍化逆向发展的越好。当农田耕种时间和地下水埋深低于临界值的时间超过20年时,盐渍土基本可以自然恢复为非盐渍土。空间特征表现在,由绿洲下部向上部,土壤盐渍化逆向演替阶段逐渐向高级过渡。  相似文献   

8.
农田防护林作为提高生态环境效益的有效农业管理方式，对改善土壤理化性质、改善生态环境，提高作物产量具有重要意义。在河套灌区选择三种典型农田防护林(4行林带、5行林带和8行林带)测量了2019—2021年生长季农田内距防护林0.3 H、0.7 H、1 H、2 H、3 H和4 H处0～100 cm的土壤性质和防护林与农田的植被属性，测算了土壤水分储量(SMS)和土壤养分储量[碳储量(SCS)、氮储量(SNS)和磷储量(SPS)]。结果表明：(1)不同防护林系统水平方向上的土壤容重和土壤黏粒含量差异显著，在垂直方向上土壤属性均有显著差异。(2)防护林具有较好的保水性和养分供应功能，其中4行林带的土壤水分储量和养分储量高于其他林带，分别为SMS 237.44 mm、SCS 544.93 g·m-2、SNS 953.72 g·m-2和SPS 859.04 g·m-2。(3)4行林带的整体长势比较好，其平均树高为30.06 m，胸径为0.41 m，且4行防护林的作物产量最高，为15.75 t·hm-2。(4)冗余...  相似文献   

9.
为探明咸水灌溉对土壤水盐分布及设施番茄植株生长、产量和品质的影响,本试验以南疆地区设施番茄为研究对象,设置4个灌溉水矿化度,分别为2 g·L-1（T1）、4 g·L-1（T2）、6 g·L-1（T3）和8 g·L-1（T4）,并以淡水灌溉为对照（CK）,开展同一灌水定额条件下设施番茄适宜灌水矿化度的研究。结果表明：不同生育期阶段土壤含水率基本表现为20～60 cm土层较高,表层及深层土壤含水率相对较低,土壤含水率随着灌水矿化度的增大逐渐增加;0～80 cm土层平均土壤含水率在生育期内逐渐降低,且深层土壤降幅显著;生育期初始阶段土壤含盐量主要积聚在0～40 cm土层,随着生育期的推进土壤盐分呈累积趋势且向深层土壤运移,生育期末主要积聚在0～60 cm土层;灌水矿化度小于4 g·L-1时0～20 cm土层整体呈脱盐状态,其中CK处理平均脱盐率达27.79%,T1处理平均脱盐率达17.07%;灌水矿化度2～4 g·L-1促进了番茄植株生长,株高和茎粗相较CK分别...  相似文献   

10.
荒漠植被是河西走廊绿洲生态安全防护的重要屏障,研究荒漠植被组成及土壤养分分布特征对于荒漠—绿洲过渡带荒漠植被建设及管理有重要意义。本研究基于大量野外调查,并使用传统统计学与地统计学方法,研究了河西走廊中段及巴丹吉林沙漠南缘荒漠植被组成及土壤养分特征,并解析了其与环境因子的相关关系。结果表明：河西走廊中段及巴丹吉林沙漠西南缘荒漠区植物组成单一,多样性较低,且植物种类集中在少数科中,出现频度高的植物均为红砂(Reaumuria songarica)和白刺(Nitraria tangutorum)等典型荒漠植物。草本植物分布与年均降水量有较强相关性,研究区最南端的山丹县草本生物量达到108.01 g·m-2,在一定年降水量区间,灌木生物量随降水增加而增加,最高值出现在靠近祁连山北坡的肃州区,为134.03 g·m-2;降水量的增加,会显著促进草本植物的生长。研究区表层土壤有机碳、总氮、总磷含量最高,其平均值分别为2.12 g·kg-1、0.25 g·kg-1、0.41 g·kg-1,...  相似文献   

11.
In 1975 many tumours were observed in plants ofBegonia Schwabenland grown in Aalsmeer. Submersion of the roots ofNicotiana megalosiphon seedlings in a homogenate of tumorous tissue, induced tumours after two weeks. Short periods of submergence yielded results similar to those obtained after longer periods. Tumour homogenates lost their infectivity after ten min at 50°C. Aphids transmitted the infectious agent.Treatment with propylene oxide did not inhibit infectivity completely. Filtration through a 450 nm filter removed the infectious agent.Tobacco tumor virus or a viroid could not be isolated. Cultures ofCorynebacterium fascians, isolated from tumours ofN. megalosiphon were highly infectious and induced tumours in healthyN. megalosiphon andBegonia. Tumorous tissue homogenates ofPelargonium zonale, Dahlia sp.,Gladiolus sp., andLilium sp. also caused tumours inN. megalosiphon, from whichC. fascians was isolated. It was not possible to produce tumours inN. megalosiphon with homogenates from roses with symptoms of bud proliferation.Samenvatting In 1975 werden vele tumoren waargenomen inBegonia Schwabenland op Aalsmeerse bedrijven (Fig. 1). De infectiositeit van tumorweefsel kon goed en snel worden vastgesteld door de wortels van zaailingen vanNicotiana megalosiphon in een homogenaat van tumorweefsel te dompelen. Tumoren ontstonden na twee weken, de eindbeoordeling geschiedde na een maand (Fig. 2). Ook verschillende andereNicotiana spp.,Melilotus officinalis (Fig. 3) enPisum odoratum (Fig. 4) werden aangetast.Bij de infectiositeitstoets gaven zeer korte dompeltijden even goede resultaten als langere (Tabel 1). Infectieus sap verloor zijn infectievermogen na 10 min verhitting bij 50°C. Bladluizen brachten de smetstof over. Propyleenoxide verminderde de infectiositeit wel, doch onderdrukte deze niet totaal. Bij filtratie door een 450 nm filter bleef het infectieuse agens op het filter achter. Het tumor-inducerende agens was ook aanwezig in die delen van planten met tumoren welke gezond leken en het ging voor een gering deel over met zaad (Tabel 2).Uit tumoren konden wij geen tabakstumorvirus of een viroïde isoleren. Culturen vanCorynebacterium fascians, geïsoleerd uit tumoren vanN. megalosiphon bleken zeer infectieus en veroorzaakten tumoren inN. megalosiphon enBegonia. Homogenaten van tumorweefsel vanPelargonium zonale, dahlia (Fig. 5), gladiool (Fig. 6) enLilium Mid Century Hybrid Enchantment (Fig. 7) veroorzaakten ook tumoren opN. megalosiphon, waaruitC. fascians werd geïsoleerd. Met sap van kroeskopzieke rozen konden wijN. megalosiphon niet besmetten.  相似文献   

12.
Plant Viruses Transmitted by Whiteflies   总被引：18，自引：0，他引：18  
One-hundred and fourteen virus species are transmitted by whiteflies (family Aleyrodidae). Bemisia tabaci transmits 111 of these species while Trialeurodes vaporariorum and T. abutilonia transmit three species each. B. tabaci and T. vaporariorum are present in the European–Mediterranean region, though the former is restricted in its distribution. Of the whitefly-transmitted virus species, 90% belong to the Begomovirus genus, 6% to the Crinivirus genus and the remaining 4% are in the Closterovirus, Ipomovirus or Carlavirus genera. Other named, whitefly-transmitted viruses that have not yet been ranked as species are also documented. The names, abbreviations and synonyms of the whitefly-transmitted viruses are presented in tabulated form together with details of their whitefly vectors, natural hosts and distribution. Entries are also annotated with references. Whitefly-transmitted viruses affecting plants in the European–Mediterranean region have been highlighted in the text.  相似文献   

13.
The epidemiology ofSitobion avenae and its natural enemies in winter wheat was studied in 1975, 1976 and 1977. Immigration was important until the end of flowering. The alate immigrants had apterous offspring. These became the driving force in population growth. Their offspring were mostly alatae which usually left the field. A model of the epidemic was developed. Quantitative relations between the aphids and their environment were obtained from literature or established in laboratory trials. The model simulated population development and population composition from the beginning of June till the population peak at the end of June or early in July. Because quantitative data on relations between aphids and their natural enemies and pathogens are scarce, and since the knowledge on wing formation is still limited, the population collapse could not be predicted. In the future, prognosis over a period of three weeks seems possible.Samenvatting De toenemende betekenis van graanbladluizen (vooralSitobion avenae) gepaard gaande met een sterke toename van het gebruik van insecticiden op granen maakte verbetering van de prognose over het schadelijk optreden wenselijk. Door gedetailleerde tellingen in het veld (Fig. 1–7) werden gegevens verkregen over het verloop van de epidemie en het optreden van natuurlijke vijanden in 1975, 1976 en 1977.Een immigratieperiode tot in de bloei kon worden vastgesteld. Daarna lijkt de aantrekkelijkheid van het gewas voor alate luizen te verminderen. De alate immigranten krijgen aptere nakomelingen. Deze vormen de stuwende kracht van de populatiegroei. De nakomelingen van apteren zijn merendeels alaat. Zij verlaten het gewas.Een model van de populatieontwikkeling gedurende de epidemie werd opgesteld. De relatiediagrammen Fig. 9 en 10 laten groei en ontwikkeling vanS. avenae en een predator (Syrphus corollae) zien. Kwantificering van de betrekkingen werd mogelijk door literatuurgegevens en laboratoriumexperimenten.Met het model kon de populatieontwikkeling vanS. avenae vanaf begin juni tot aan de populatiepiek in 1975, 1976 en 1977 vrij goed worden gesimuleerd (Fig. 12). Ook de populatieopbouw kon worden gesimuleerd (Fig. 14). De teruggang van de populatiedichtheid blijkt moeilijker te voorspellen door het ontbreken van gegevens over natuurlijke vijanden.Het lijkt waarschijnlijk dat in de toekomst met het model een prognose over de piek van de bladluispopulatie circa 3 weken tevoren mogelijk zal zijn.  相似文献   

14.
During a survey conducted from 1998 to 2002, Fusarium proliferatum was found associated with young and adult palms belonging to the genera Chamaerops, Phoenix, Trachycarpus and Washingtonia showing symptoms of wilt and dieback. The fertility and toxicological profile of 36 strains representing different locations and hosts were studied. All of them except two, which were infertile, belonged to mating population D. Both mating types (MATD-1 and MATD-2) were isolated from the same host species, showing a high potential of genetic recombination in the field. Additionally, eight strains were fertile once crossed as female. Toxin analysis showed differences in the ability of strains to produce fumonisin B1, moniliformin, beauvericin, fusaric acid and fusaproliferin. Only 17 of them produced all the toxins analyzed. Pathogenicity tests were conducted on Phoenix dactylifera and P. canariensis using nine F. proliferatum Spanish strains and two reference strains from Saudi Arabia. Eight months after inoculation all strains caused disease, with palms showing lesions on the bases of leaves and development of wilt symptoms similar to those originally observed in affected plants. This is the first report on the occurrence of F. proliferatum on P. dactylifera in Spain and also the first report of this pathogen on C. humilis, P. canariensis, P. reclinata, T. fortunei, W. filifera and W. robusta.  相似文献   

15.
Barley yellow dwarf disease is one of the most important problems confronting cereal production in Iran. Barley yellow dwarf virus-PAV (BYDV-PAV) and Cereal yellow dwarf virus-RPV (CYDV-RPV) are the predominant viruses associated with the disease. One isolate of BYDV-PAV from wheat (PAV-IR) and one isolate of CYDV-RPV from barley (RPV-IR) were selected for molecular characterisations. A genome segment of each isolate was amplified by PCR. The PAV-IR fragment (1264 nt) covered a region containing partial genes for coat protein (CP), read through protein (RTP) and movement protein (MP). PAV-IR showed a high sequence identity to PAV isolates from USA, France and Japan (96–97%). In a phylogenetic analysis it was placed into PAV group I together with PAV isolates from barley and oats. The fragment of RPV-IR (719 nt) contained partial genes for CP, RTP and MP. The sequence information confirmed its identity as CYDV. However, RPV-IR showed 90–91% identity with both RPV and Cereal yellow dwarf virus-RPS (CYDV-RPS). Phylogenetic analyses suggested that it was more closely related to RPS. These data comprise the first attempt to characterise BYD-causing viruses in Iran and southwest Asia. The nucleotide sequence data reported appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers AY450425 and AY450454  相似文献   

16.
Corynebacterium fascians, which causes leafy gall, has been shown to be responsible for the unusual symptoms recently found in lilies. The symptoms are described and the different bacterial isolates compared by biochemical, serological and pathogenicity experiments. No evidence could be found for the existence of specialized strains even though considerable variation in virulence could be demonstrated. Although the role of variation in susceptibility of the different lily cultivars should not be underestimated, it would appear that high inoculum levels ofC. fascians in the soil may be largely responsible for these outbreaks.Also included in this study are the results of biochemical, serological and pathogenicity experiments ofC. fascians which has been isolated fromKalanchoe, Euphorbia, Brodiaea, Hebe andVerbascum.Samenvatting Reeds een aantal jaren was in lelies een woekering in stengelbollen bekend, die echter sporadisch voorkwam en economisch van weinig betekenis was. Tijdens de zomer van 1977 echter trad de ziekte op één enkel perceel zo ernstig op dat zeer aanzienlijke oogstderving het gevolg was. Behalve de stengelbol kan ook de hoofdbol misvormd zijn. Bovendien kunnen misvormde stengelbollen lange spruiten vormen, zgn. sabeltandvorming. Soms is het wortelstelsel gereduceerd; in de kas zijn verdikte stengels waargenomen. De ziekte staat nu bekend onder de naam woekerziekte.Door de PD te Wageningen en het LBO te Lisse werd de bacterieCorynebacterium fascians (Tilford) Dows. uit het zieke materiaal geïsoleerd. In gezamenlijk onderzoek werd nagegaan of de bacterie de veroorzaker is van bovengenoemde symptomen en of hier sprake is van een op lelie gespecialiseerde stam.Biochemische en serologische vergelijkingen tussen isolaten vanC. fascians uit lelie,Kalanchoe, Euphorbia, Brodiaeea, Hebe enVerbascum laten zien dat er zeer weinig verschillen bestaan. Alle isolaten reageren op een standaard antiserum met titers variërend tussen 1: 640–1: 5120.Een oriënterende inoculatieproef werd uitgevoerd op het LBO in 1977. Daarna werden op de PD 10 van de 25 isolaten uit lelie en 8 uit andere waardplanten getoetst op lelie, chrysant en lathyrus. Uit de inoculatieproeven blijkt, dat de bacterie de veroorzaker is van de waargenomen symptomen. Tussen de isolaten blijkt een groot verschil in pathogeniteit te bestaan (12–100% aantasting), zonder dat dit aan herkomst gebonden is. Het voorkomen van op lelie of andere waardplanten gespecialiseerde stammen is daarom niet aan te nemen.In hoeverre de hevige aantasting een gevolg is van een opbouw van de bacterie-populatie door een te nauwe vruchtwisseling en mechanische rooimethoden moet worden nagegaan.  相似文献   

17.
Organic amendments and green manure are potential alternatives to the harmful chemical control means currently used against plant-parasitic nematodes. In this work, Chrysanthemum coronarium was applied to the soil as a green manure to control the root-knot nematodes Meloidogyne incognita and M. javanica. Chrysanthemum coronarium significantly reduced nematode infection of tomato roots and improved plant-top fresh weight, both in the greenhouse and in microplots. Other green manures, derived from Anthemis pseudocotula, wild chickpea (Cicer pinnatifidum), Geranium spp. and wheat, were not as effective as C. coronarium. Chrysanthemum coronarium, retained its nematicidal activity even when applied as a dried material. Only mature C. coronarium plants, in their flowering stage, exhibited nematode control activity, but the green plant parts were more effective than the flowers. An aqueous extract of C. coronarium exhibited in vitro, nematostatic activity towards M. incognita and M. javanica second-stage juveniles and inhibited their hatching from eggs and egg-masses; its nematostatic activity was expressed also against other phytonematode species such as Heterodera avenae and Pratylenchus mediterraneus, but did not affect the beneficial entomopathogenic nematode Steinernema feltiae.  相似文献   

18.
Broad bean mottle virus (BBMV) was transmitted from infected to healthy faba-bean plants by the curculionid weevilsApion radiolus Kirby,Hypera variabilis Herbst,Pachytychius strumarius Gyll,Smicronyx cyaneus Gyll, andSitona lineatus L. The latter appeared to be an efficient vector: acquisition and inoculation occurred at the first bite, the rate of transmission was c. 41%, and virus retention lasted for at least seven days.S. lineatus transmitted the virus from faba bean to lentil and pea, but not to the three genotypes of chickpea tested. This is the first report on the generaHypera, Pachytychius, andSmicronyx as virus vectors, and onA. radiolus, H. variabilis, P. strumarius, andS. cyaneus as vectors of BBMV.Out of 351 samples of food legumes with symptoms suggestive of virus infection, 16, 11, 19, and 17% of the samples of chickpea, lentil, pea, and common bean, respectively, were found infected when tested for BBMV in DAS-ELISA. This is the first report on the natural occurrence of BBMV in chickpea, lentil, pea, and common bean. The virus should be regarded as a food-legume virus rather than a faba-bean virus solely, and is considered an actual threat to food legume improvement programmes.  相似文献   

19.
浅黄恩蚜小蜂和丽蚜小蜂对温室白粉虱的寄生潜能分析   总被引：1，自引：1，他引：0  
浅黄恩蚜小蜂Encarsia sophia GiraultDodd和丽蚜小蜂Encarsia formosa Gahan是防治粉虱类害虫的优势寄生蜂,通过生命表技术方法分析了2种寄生蜂对温室白粉虱Trialeurodes vaporariorum(Westwood)的防治潜能。结果表明,丽蚜小蜂在羽化第3天和第10天出现2次寄生高峰,占其总寄生量的13.7%和8.0%,在2次高峰之间逐日寄生粉虱数量比较平稳,单雌逐日平均产雌数保持在10.6~13.4头,10 d后寄生量呈明显的下降趋势;而浅黄恩蚜小蜂羽化10 d内逐日寄生粉虱量变化不大,单雌逐日产雌数稳定在4.2~5.4头,羽化14 d后寄生量呈明显下降趋势。丽蚜小蜂和浅黄恩蚜小蜂的R0、T、rm、λ值分别为171.5、18.0、0.2854、1.3303和61.6、16.2、0.2544、1.2897;粉虱若虫充足时,丽蚜小蜂平均单雌寄生若虫数是浅黄恩蚜小蜂的2.7倍,而后者平均单雌取食若虫数为60.6头,明显高于前者42.7头,总的来看,丽蚜小蜂通过寄生和取食杀死粉虱总量220.8头,明显高于浅黄恩蚜小蜂的127.9头。表明在应用寄生蜂防治温室白粉虱时,单独释放丽蚜小蜂比浅黄恩蚜小蜂显示出更好的防治潜能。  相似文献   

20.
Tsror  Leah  Aharon  M.  Erlich  Orly 《Phytoparasitica》1999,27(3):215-226
Potato seed tubers are imported to Israel from northern Europe and planted in spring; tubers harvested early from the spring crop are used as seed for the autumn crop. Although only seed lots registered as certified are imported, a previous survey (1984–1994) indicated that most imported lots were affected by latent or active infections caused byErwinia carotovora,Streptomyces scabies, Rhizoctonia solani, Fusarium spp. andSpongospora subterranae. The survey was extended until 1998, and included additional pathogens:Ralstonia solanacearum,Helminthosporium solani, Colletotrichum coccodes andVerticillium dahliae. Most of these pathogens were also monitored in domestic seed tubers, and are reported for the first time. Brown rot was not observed in any of the imported lots. Blackleg and soft rot caused byErwinia spp. were detected in most of the imported lots; however, less than 7% of the lots were contaminated at high levels, while approximately 65% were contaminated at moderate levels. Common scab was detected in most of the imported lots; 51% of the imported lots were contaminated at moderate or high levels, whereas only 6.5% of the domestic seed lots were contaminated at these levels. Black scurf was detected in most of the imported lots; on average, 47.3%, 44.2% and 1.4% of the lots were contaminated at low, moderate and high levels, respectively, and only 7.1% were disease-free. In contrast, most of the domestic lots were either disease-free (45.4%) or had a low disease incidence (37.3%). Only 16.7% of the lots were moderately infected and 0.2% were highly contaminated. Silver scurf was observed in most of the imported lots during all years of the survey, with no differences among the producing countries; on average, 22.7%, 66.1% and 7.5% of the lots were contaminated at low, moderate and high levels, respectively, and only 3.7% were disease-free. Most of the domestic lots (76%) were disease-free and only 6.6% were infected at moderate or high levels. Black dot was observed in a considerable portion of the shipments from Holland during all years of the survey, particularly in 1998, when 34% of the lots were infected. The shipments from France and Germany were infected at low levels, except in 1998, when 19% and 11% of the lots, respectively, arrived infected. In shipments from Scotland and Ireland low incidences of the disease were observed in 1994 and 1995. In the domestic lots, black dot incidence was low (<2.4%) except in 1996, when 11% of the lots were infected.V. dahliae was monitored only in domestic seed tubers. The incidence of disease-free lots was 56–64%, whereas in 20–30% of the lots the level of infection was <5%, and in 6–16% of the lots the level was >5%. The survey findings demonstrate transmission of seedborne pathogens; most of these pathogens can become established in the soil and eventually cause severe outbreaks of disease in potatoes grown in Israel. http://www.phytoparasitica.org posting May 16, 1999.  相似文献   

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