七星瓢虫的抗药性选育及其生物学特性研究

为了明确七星瓢虫对吡虫啉的抗性发展动态,在室内选用吡虫啉逐代筛选,选育抗吡虫啉的七星瓢虫品系。发现七星瓢虫对吡虫啉的抗性整体呈上升趋势,但抗性不稳定,选育20代后抗性为63.1519倍。同时为了明确七星瓢虫对吡虫啉产生抗性后对其生物学特性的影响,将抗性选育13代的七星瓢虫品系与敏感七星瓢虫品系、野外七星瓢虫种群进行生物学特性的比较,结果表明,从幼虫的整个发育历期来观察,抗性品系幼虫的发育历期为12.36 d,野外种群为9.88 d,敏感品系为10.62 d,3者之间差异显著;蛹发育历期3者之间没有差异;4龄老熟幼虫、蛹、初羽化雌成虫、初羽化雄成虫平均体重3组间有一定的差异;七星瓢虫抗性品系、敏感品系、野外种群前期的卵孵化率分别为63.0%、62.4%和66.3%,中期的卵孵化率分别为64.8%、58.7%和75.6%,后期的卵孵化率分别为69.3%、57.4%和75.5%,3组之间无显著差异;抗性品系雌成虫的平均产卵量为1043.3粒,敏感品系为1100.2粒,野外种群雌成虫为1250.1粒,3者之间没有显著差异。综上所述,抗药性对七星瓢虫的生物适合度有一定程度的影响,但是,由于抗性倍数较低,影响尚不明显。     

取食阶段和食物类型对大草蛉幼虫发育的影响

集团内捕食是食蚜天敌群落中常见的现象,而捕食性昆虫卵通常成为集团内的猎物。为探究新疆农田生态系统中捕食性昆虫集团内捕食的规律,以大草蛉(Chrysopa pallens)为对象,设置不同幼虫期(整个幼虫期、刚蜕皮的4龄幼虫)和食物类型〔七星瓢虫(Cocinellina septempuntata)卵、棉蚜(Aphis gossypii)+七星瓢虫卵、棉蚜〕等2因素3水平的析因实验设计处理,观察比较大草蛉发育、存活参数。结果表明:食物类型与饲喂期存在显著互作,影响大草蛉幼虫发育至成虫的存活概率,即食物类型的影响程度取决于饲喂期的长短,虽然在整个幼虫期和4龄幼虫期处理下,存活率在"棉蚜"与"瓢虫卵+棉蚜"处理之间没有差异,但大于"瓢虫卵"处理下的存活率,但差异幅度不同:"整个幼虫饲喂"处理下的存活率大于"4龄期饲喂"处理。说明干旱环境中大草蛉幼虫无论早晚只捕食七星瓢虫卵均难以正常发育存活至成虫。     

利用人工卵赤眼蜂蛹规模化饲养七星瓢虫的可行性研究

利用人工卵赤眼蜂蛹规模化饲养七星瓢虫的结果表明：（1）人工卵赤眼蜂蛹基本上能满足七星瓢虫幼虫的生长发育，并能正常羽化，但发育历期延长2.7d，蛹重降低；（2）成虫取食人工卵赤眼蜂蛹后，产卵前期、产卵期、总产卵量分别为12.3d、45.6d和1589.7粒，与蚜虫对照组差异显著。（3）用人工卵赤眼蜂蛹连续饲养七星瓢虫至6代时，生殖力有明显退化。（4）幼虫期饲喂人工卵赤眼蜂蛹、成虫期饲喂蚜虫与幼虫期及成虫期均用蚜虫饲喂的七星瓢虫具有相似的生殖力。（5）用人工卵赤眼蜂蛹饲养成虫，添加取食刺激剂（5%的蔗糖 0.1%橄榄油）后，其生殖力接近用蚜虫饲养的水平。综上所述，人工卵赤眼蜂蛹可满足幼虫的生长育，但对成虫的生殖力有一定影响；连代饲养后出现退化现象，这些影响主要是成虫产卵前期的营养得不到满足，可通过在成虫期添加取食刺激剂或成虫产卵前期改喂蚜虫解决。     

卵和蛹短时高温对草地贪夜蛾生长发育的影响

为明确草地贪夜蛾Spodoptera frugiperda卵和蛹经短时高温处理对其生长发育的影响,将草地贪夜蛾卵和蛹在34、38、42、46℃高温下分别处理2、4、6 h后,测定短时高温下草地贪夜蛾卵的孵化率、不同虫态的发育历期、蛹的羽化率和雌成虫及其子代的繁殖力等指标。结果表明:随着温度升高和高温持续时间延长卵的孵化率逐渐降低,卵在38℃及以上处理6 h或高温46℃处理2 h以上孵化率显著降低;46℃处理6 h的孵化率最低为12.21%,幼虫不能成活;在42℃处理4 h以上和46℃处理2 h以上卵的发育历期延长,与对照差异显著,幼虫的发育历期显著短于对照,蛹的发育历期与对照比无显著差异;38℃处理6 h、42℃处理6 h成虫的产卵量显著低于对照。短时高温处理蛹后,雌蛹和雄蛹在46℃处理2～6 h后羽化率分别为0～15.00%和0～6.75%,均显著低于对照,雌蛹在42、46℃下的羽化率高于雄蛹,蛹在38℃处理6 h和42℃处理2 h以上后羽化的成虫产卵量较低,为121.25～186.75粒。表明高温38℃以上持续6 h或42℃以上持续2 h以上草地贪夜蛾种群生长会受到抑制。     

非昆虫源人工饲料对异色瓢虫生物学特性的影响

为明确一种非昆虫源人工饲料对异色瓢虫的饲养效果,以豌豆蚜为对照,研究了该人工饲料对异色瓢虫生长发育和生殖能力的影响。结果表明,取食人工饲料的异色瓢虫从卵到成虫的累计存活率达到82.2%,饲喂蚜虫的对照组为71.1%;与对照组相比,取食人工饲料的异色瓢虫幼虫总历期延长(人工饲料16.24 d,对照12.47 d),蛹重减轻(人工饲料27.74 mg,对照33.93 mg),成虫寿命延长(人工饲料雌虫103.6 d,雄虫82.9 d;对照雌虫85.7 d,雄虫77.1 d),10 d累计产卵23.5粒,约为对照组的5%,但人工饲料对异色瓢虫的羽化率和后代卵的孵化率无显著影响;幼虫期饲喂人工饲料、成虫期改喂蚜虫的异色瓢虫10 d产卵量352.1粒,约为对照组的80%。本研究所用人工饲料能提高异色瓢虫幼虫存活率和成虫寿命,且幼虫期取食人工饲料对成虫期产卵量影响较小,因此适于作为异色瓢虫人工饲养中幼虫阶段的食物。     

四斑小毛瓢虫生物学特性初探

本文观察了四斑小毛瓢虫Scymnus frontalis各虫态的形态特征和生活习性,比较了其在不同温度下的发育历期,取食桃蚜Myzus persicae、大豆蚜Aphis glycines、麦长管蚜Macrosiphum avenae和刺槐蚜A.robiniae对其捕食量和幼虫发育历期的影响。在182、02、32、62、9℃条件下,四斑小毛瓢虫卵到成虫的发育时间分别为32.91、27.18、22.23、17.25、14.93d。四斑小毛瓢虫幼虫对桃蚜、大豆蚜、麦长管蚜、刺槐蚜的捕食量分别为82.97、64.70、58.57、76.11头;相应发育历期分别为9.80、10.901、0.86、9.86d。在26℃、RH70%的条件下,用桃蚜饲养四斑小毛瓢虫效果最好,成虫获得率达88%。四斑小毛瓢虫的卵期、幼虫期、蛹期及产卵前期的发育起点温度和有效积温分别为12.875、.45、11.72、14.41℃和40.94、210.915、8.54、54.42日度。     

七星瓢虫不同虫态的低温贮藏条件

为了探究七星瓢虫不同虫态的低温贮藏条件，本研究在不同恒定低温-时间与变温预处理后恒定低温-时间组合下分别测定了七星瓢虫卵、蛹及成虫的孵化率、羽化率及成虫存活率。结果表明，无论恒定低温或变温预处理，卵在常温下3 d均可孵化，恒温和变温的孵化率分别为72.56%和73.93%，且当保存时间不超过5 d时，卵在8℃、10℃及12℃时孵化率均在50%以上，保存时间为10 d时，卵在10℃及12℃时孵化率均在50%以上。七星瓢虫蛹在恒温和变温预处理条件下，在10℃保存3 d时均可完全羽化，且羽化率与对照组无显著差异，但当保存时间达到50 d，恒定温度在2℃、4℃、6℃和8℃下畸形率达到了100%，而其余保存天数下均未出现畸形率，当变温预处理后，仅在2℃下保存20、30和50 d分别出现100%、50%和100%的畸形率。在25℃保存时，恒温和低温预处理下的成虫保存40 d时，全部死亡，但恒温8℃下保存60 d和变温预处理10℃下保存60 d的成虫存活率分别达到60.46%和63.29%。综合分析表明，一定时间下的恒定低温和变温预处理保存均能延长七星瓢虫卵、蛹及成虫寿命，从而为七星瓢虫不同虫态商品化及其货架期的延长提供有效支持。     

龟纹瓢虫残食同种卵行为的研究

本文初次研究了龟纹瓢虫残食同种卵的行为。结果表明:龟纹瓢虫幼虫和成虫均有明显的残食同种卵行为。初孵幼虫取食2粒卵即可完成一龄发育,但生存时间明显延长。以其卵作食料可完成幼虫发育,但发育历期较慢;成虫残食同种卵则无生殖能力。因此认为,当自然界缺乏猎物时,龟纹瓢虫卵可作为增加它的生存机会及种群延续的一种替换食料。这种残食同种卵行为对于种群自我调节和繁衍有着重要的生物学意义。     

温度对蠋蝽Arma chinensis及其子代生物学特性的影响

通过室内试验,设置了低温0℃处理蠋蝽(Arma chinensis)成虫12 h后于25℃饲养、3龄若虫至成虫分别于18、25℃及35℃条件下饲养等试验,以研究温度对蠋蝽生物学特性的影响。结果表明:(1)成虫短暂低温(0℃,12 h)处理后,其子代3龄至5龄若虫的发育历期为27.6 d,略高于持续低温18℃处理后子代3龄至5龄若虫的发育历期(22.0 d),但35℃的高温处理则显著缩短了子代3龄至5龄若虫的发育历期(11.0 d)。(2)成虫经短暂低温后处理后,蠋蝽成虫的寿命显著延长,雌性寿命略短于雄性(雌性66.9 d,雄性69.7 d);高温(35℃)处理则显著缩短了子代成虫寿命,雄性寿命显著长于雌性(雌性22.7 d,雄性32.7 d)。(3)蠋蝽成虫经短暂低温(0℃,12 h)处理后,蠋蝽成虫的性比为雌性∶雄性=0.48∶0.52。(4)蠋蝽成虫在18℃(43粒)与35℃(32粒)温度饲养条件下的产卵量显著低于短暂低温(0℃,12 h)后成虫(约264粒)及25℃(约218粒)饲养条件下的成虫产卵量,但在几种温度处理条件下,卵的长或宽之间无显著差异。18℃低温及35℃高温处理均会显著降低卵孵化率,35℃高温条件下,蠋蝽卵的孵化率为0。     

两种替代猎物对日本刀角瓢虫生长发育及生殖力的影响

为明确替代猎物对日本刀角瓢虫人工饲养的效果，以烟粉虱卵为对照，研究了地中海粉螟卵和米蛾卵对日本刀角瓢虫生长发育及繁殖力的影响。结果表明，饲喂米蛾卵的日本刀角瓢虫存活率为17.16%，发育历期显著延长，雌虫寿命显著缩短；饲喂地中海粉螟卵处理的存活率为77.82%，雌虫寿命显著延长。瓢虫幼虫期和成虫期营养对成虫产卵能力有明显影响：幼虫期饲喂地中海粉螟卵，成虫期分别饲喂米蛾卵和地中海粉螟卵，产卵量极显著降低（分别为64.45粒和53.82粒）；幼虫期饲喂地中海粉螟卵，成虫期饲喂烟粉虱卵，产卵量（539.10粒）与对照组无显著差异；幼虫期饲喂烟粉虱卵，成虫期分别饲喂地中海粉螟卵和米蛾卵，产卵量极显著降低（分别为59.30粒和71.38粒）。因此，米蛾卵不适于日本刀角瓢虫饲养，地中海粉螟卵可作为瓢虫幼虫期饲养的替代猎物。     

Epidemiology and simulation of population development of Sitobion avenae in winter wheat

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.     

Tumours of Begonia and some other ornamentals,induced by Corynebacterium fascians

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.     

Nematicidal Activity of Chrysanthemum coronarium

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.     

Effects of the saprophytic leaf mycoflora on growth and productivity of winter wheat

The effects of the saprophytic mycoflora and its interference with cereal aphids on growth and yield of winter and spring wheat was studied in field experiments in 1980, 1981 and 1982.Yields varied between 5000 and 8000 kg dry matter of kernels per ha. The effect of the saprophytic mycoflora on yield was determined in different treatments: A) no control measures against cereal aphids and saprophytic and necrotrophic fungi, B) no control of cereal aphids, control of saprophytic and necrotrophic fungi, C) control of cereal aphids and control of saprophytic and necrotrophic fungi, D) control of cereal aphids and stimulation of saprophytic mycoflora and E) control of cereal aphids, no control of saprophytic and necrotrophic fungi nor stimulation of saprophytic mycoflora.Considerable differences in top densities of saprophytic mycoflora (10 times as large in A and D as in B and C) were determined. The consequences of these differences for the growth and productivity of wheat were minor. A negative effect of saprophytic mycoflora on the yield could not be detected in 1981 and 1982, whereas a small positive significant effect was found in 1980. This stimulation may have been due to competition between necrotrophic fungal pathogens and saprophytic mycoflora. As a result of favourable weather conditions necrotrophic fungal pathogens were very numerous in 1980 and could form an important yield reducing factor. Yield levels may effect the importance of the necrotrophic and saprophytic mycoflora as yield reducing factors. Additionally, in the presence of aphid honeydew captafol was found to be relatively ineffective against saprophytic fungi.     

Aetiology and causal agents of mango sudden decline disease in the Sultanate of Oman

Mango sudden decline is a recently introduced, economically serious disease in Oman. Affected mango trees have wilting symptoms that usually begin on one side and later spread to involve the entire tree. Trees exude amber-coloured gum from the bark of their trunks or branches and vascular tissues are discoloured. Having entered Oman in the recent past, survey data is presented that shows the disease to have spread throughout the northern part of the country. Evidence is presented that the vascular wilt pathogen Ceratocystis fimbriata causes mango sudden decline disease in Oman, possibly in concert with Lasiodiplodia theobromae and the recently described Ceratocystis omanensis. Isolates of these fungi from affected trees, cause infection and can be recovered from inoculated seedlings. Bark beetles (Hypocryphalus mangiferae) are shown to carry C. fimbriata and L. theobromae and are presumably responsible for transmitting both pathogens to healthy mango trees. Acting as a wounding agent and vector, the bark beetle is likely to have assisted the rapid spread of the disease across Oman.     

Relationship Between Production of the Phytotoxin Prehelminthosporol and Virulence in Isolates of the Plant Pathogenic Fungus Bipolaris sorokiniana

A gas chromatographic method was developed to quantify the phytotoxin prehelminthosporol, which is a sesquiterpene metabolite of the plant pathogen Bipolaris sorokiniana. The toxin was extracted from mycelium or culture filtrates, pre-cleaned using solid phase extraction, and analyzed by gas chromatography as a trimethylsilyl-derivative. The detection limit of the method was 5ngl^–1 (signal to noise ratio 4:1) which corresponds to ca. 15ng prehelminthosporol per mg dry weight of mycelium or 15ng prehelminthosporol per ml culture filtrate. The total amount of prehelminthosporol (mycelium plus culture filtrate) increased with cultivation time when examined in six isolates of B. sorokiniana after 6, 9, 12 and 15 days of incubation. The screening experiment of 17 isolates for prehelminthosporol production after 8 days of incubation revealed significant differences in the toxin production between the isolates. The isolates with low toxin production had lower virulence towards barley roots compared to those with higher production of the toxin. However, the virulence did not increase with prehelminthosporol level among the high producing isolates. Prehelminthosporol was also analyzed in a number of related Bipolaris and Drechslera species. In addition to B. sorokiniana, three out of six Bipolaris species (B. setariae, B. zeicola, B. victoriae) produced prehelminthosporol, which indicates that ability to produce prehelminthosporol is conserved among closely-related Bipolaris species.     

Inactivation of soil-borne plant pathogens during small-scale composting of crop residues

Samples of heavily infested crop residues were incorporated in static compost heaps (2.5–4.6 m³) of the Indore type. Temperature increased to 50–70°C within 6 days depending on the type of crop residues used and the location within the heap. The heat phase (>40 °C) lasted 2–3 weeks and was followed by a c. 5-months maturation phase (<40 °c).=" among=" the=" 17=" pathogens=" tested,=">Olpidium brassicae and one of the four formae speciales ofFusarium oxysporum that were tested survived composting, but also their inoculum was greatly reduced.Survival during specific phases of composting was studied by incorporation and retrieval of samples at various stages of the process.F. oxysporum f. sp.melonis was completely inactivated andO. brassicae andPlasmodiophora brassicae were almost completely inactivated during the short heat phase. The three pathogens survived the long-lasting maturation phase without loss of viability. Heat evolved during composting was found to be the most important factor involved with sanitation of crop residues. The possible involvement of fungitoxic conversion products and microbial antagonism is discussed.     

Survey of Bacterial and Fungal Seedborne Diseases in Imported and Domestic Potato Seed Tubers

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.     

浅黄恩蚜小蜂和丽蚜小蜂对温室白粉虱的寄生潜能分析

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。     

Identification,incidence and characterization of <Emphasis Type="Italic">Fusarium proliferatum</Emphasis>on ornamental palms in Spain

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.