Identification of the Beet Cyst Nematode Heterodera schachtii by PCR

PCR-RFLPs of ITS-rDNA and PCR with species-specific primers were developed for identification of cysts and juveniles of the beet cyst nematode Heterodera schachtii. Restrictions of PCR product by MvaI or ScrFI distinguish H. schachtii, H. betae, H. trifolii and H. medicaginis. RFLP profiles with eight restriction enzymes for these four nematode species are presented. Based on Internal Transcribed Spacer sequences of populations from several Schachtii group species, a specific primer for H. schachtii was designed, permitting amplification of the target sequence from juveniles and cysts of the beet cyst nematode. A duplex PCR protocol tested with a wide range of nematode samples is described.     

The Effect of Different Levels of Beet Cyst Nematodes (Heterodera schachtii) and Beet Necrotic Yellow Vein Virus (BNYVV) on Single and Double Resistant Sugar Beet Cultivars

Beet cyst nematode-resistant cultivars, which were introduced recently, originated from the homozygous inbred line B883. This translocation product was unstable and the transmission of resistance when crossed with a susceptible cultivar did not exceed 94%. Tests with the resistant cultivars in climate cabinets showed a wide variety of resistance against Heterodera schachtii and beet necrotic yellow vein virus (BNYVV), expressed as average numbers of infective units per plant and percentages of resistant plants. In a series of field trials at different levels of infection of H. schachtii, their multiplication rates on all resistant cultivars depended on the initial density, which was caused by the presence of small numbers of susceptible plants. Since tolerance to wilting was also incorporated in B883, reasonable yields were obtained in the presence of H. schachtii. However, at increasing initial densities of H. schachtii, yields decreased considerably, since penetrating juveniles cause a hypersensitivity reaction in resistant plants. Based upon the results of three series of field trials, it was concluded that resistant cultivars should preferably be applied at population densities between 500 and 2000 eggs and juveniles of H. schachtii per 100ml of soil. Cultivars with double resistance against H. schachtii and BNYVV behaved like those with H. schachtii resistance in soils infected with beet cyst nematodes, but not with BNYVV. In soils with a combined infection of H. schachtii and BNYVV double resistant cultivars were far superior to single resistant ones, since damage caused by BNYVV was far more serious than damage caused by H. schachtii. No substantial interaction between soil pathogens nor types of resistance could be detected.     

Spring invasion of Heterodera schachtii in sugarbeet; a simulation study

A simulation model was developed for the spring invasion of the beet cyst nematode,Heterodera schachtii Schmidt, into sugarbeet roots, according to the state variable approach. This model describes the processes of egghatch, emergence of second stage larvae from cysts, migration to roots and penetration into roots quantitatively, using published data.In 1983 a field experiment was conducted to test this model.H. schachtii cysts were introduced at depths 6–29 cm in PVC-cylinders, buried in the soil. The rooting depth of sugarbeet seedlings, growing in these cylinders, was limited to 5 cm by 50 m mesh nylon gauze. Every 10 days the second stage larvae, which had penetrated into the roots of these seedlings were counted. After 50 days, about 40% of the eggs had hatched. More than 20% of the emerged larvae penetrated if the cysts had been buried undeeply, and only 4% if the cysts had been buried at 29 cm depth.The model predicted the course of penetration into the root during the first 40 days with reasonable accuracy (r²=0.79), but in the 5th period of 10 days the model made an overestimation of more than 100%. Egghatch after 50 days was correctly simulated. The differences in penetration into the root between the model and the experiment might result from an oversimplified simulation of the penetration success or the neglection of mortality of second stage larvae. Detailed experiments should be done to provide better parameters for these factors.Samenvatting Volgens de toestandsvariabele-benadering werd een simulatiemodel ontwikkeld van de voorjaarspenetratie van het bietecystenaaltje. Het model beschrijft aan de hand van literatuurgegevens het uikomen van de eieren, het verlaten van de cyst door de larven, de migratie naar en de penetratie in de wortel.In 1983 werd een veldproef uitgevoerd om het model te toetsen. Cysten vanH. schachtii werden op 5 dieptes tussen 6 en 29 cm ingegraven in PVC-cylinders, welke waren verzonken in de bodem. De bewortelingsdiepte van de suikerbiete-zaailingen die hierin groeiden werd beperkt tot 5 cm door nylon gaas van 50 m maaswijdte. Elke 10 dagen werden de larven geteld die in de wortels van deze plantjes waren gepenetreerd. Na 50 dagen was 40% van de eieren uitgekomen. Meer dan 20% van de gelokte larven penetreerden als de cysten ondiep waren ingegraven, en slechts 4% als de cysten op 29 cm diepte waren ingegraven.Gedurende de eerste 40 dagen werd het verloop van de penetratie in de wortel met redelijke nauwkeurigheid door het model voorspeld (r²=0.79). In de 5e periode van 10 dagen maakte het model echter een overschatting van meer dan 100%. Het uitkomen van de eieren werd correct gesimuleerd. De verschillen in penetratie tussen het model en de proef zouden het gevolg kunnen zijn van een oververeenvoudigde simulatie van het penetratiesucces of van het verwaarlozen van de mortaliteit van de migrerende larven. Betere gegevens hierover zullen moeten komen uit detailproeven.     

Rapid detection and quantification of viable potato cyst nematodes using qPCR in combination with propidium monoazide

Potato cyst nematodes (PCN), Globodera pallida and Globodera rostochiensis, are obligate parasites of solanaceous plants, causing severe losses in several potato growing areas throughout the world. To date, management of PCN is related to nematode population densities estimated as eggs per gram of soil, without considering the actual number of viable juveniles within the cysts. In classical nematology, the standard method to determine PCN viability is based on a staining assay, using Meldola's blue dye (MB) followed by microscopic visualization of MB‐treated nematodes. Although MB is considered to be reliable in staining embryonated juveniles within eggs and cysts, it is a time‐ and labour‐consuming assay. In the present work, a real‐time PCR (qPCR)‐based method combined with propidium monoazide (PMA), a photoreactive DNA‐intercalating dye, was developed for the quantification of viable PCN. This dye renders exposed DNA of dead cells unable to be amplified by PCR, and thus only DNA from viable/intact PCN juveniles is amplified and detected. The novelty of the present method lies in the simultaneous quantitative and qualitative estimation of viable PCN inocula using species‐specific primers and TaqMan probes. The PMA–qPCR viability method (v‐PCR) developed for the two Globodera species successfully discriminated dead from living specimens in heat‐treated samples and eggs in old and newly formed cysts. Interestingly, the detection of DNA from 34‐year‐old nematode cysts stored at room temperature was observed. In conclusion, the proposed v‐PCR method should prove to be very useful for the routine determination of PCN viability from field samples.     

Improved attachment and parasitism of <Emphasis Type="Italic">Trichoderma</Emphasis> on <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> in vitro

Monoclonal and polyclonal antibodies that bind to eggs and/or second-stage juveniles of the nematode Meloidogyne javanica were tested for their effects on the parasitic interactions between this nematode and the fungus Trichoderma. Parasitism of Trichoderma asperellum-203 and Trichoderma atroviride on nematode egg masses, eggs and juveniles was enhanced when antibodies were incorporated into in vitro parasitism bioassays. Parasitism on separated eggs (without gelatinous matrix) and their hatched juveniles was also improved, compared to controls without antibodies that did not attach fungal conidia. Improved parasitism could be due to bilateral binding of the antibodies to the nematodes and conidia, enabling better conidial attachment to the nematodes. Enhanced germination of antibody-bound conidia further improved parasitism. Differences were observed among antibodies in their effects on fungal parasitism and their interaction with Trichoderma species. We focused mainly on the egg- and juvenile-binding monoclonal antibody MISC that exhibited a stronger reaction with T. asperellum-203 than with T. atroviride. Pretreatment of this antibody with fucose inhibited its binding to nematodes and conidial attachment to nematodes, as well as conidial agglutination in the presence of the antibody. Antibody binding to juveniles affected their movement and viability, especially gelatinous matrix-originated juveniles. The fucose-specific lectin Ulex europaeus-I enhanced conidial attachment to nematode life-stages, and conidial agglutination occurred in its presence. These phenomena were inhibited by preincubating lectin with fucose. Our results suggest that carbohydrate residues, such as fucose, on the surface of the nematode and fungal conidia are involved in the antibody- and lectin-mediated improved parasitism.     

PCR zum halbquantitativen Nachweis von Rübenzystennematoden

Increased crop yield of nematode resistant sugar beet varieties compared to non-resistant varieties is dependent upon density of the sugar beet nematode, Heterodera schachtii, being below a certain threshold level. Therefore there is a requirement for an inexpensive quantitative laboratory test for H. schachtii. Currently the standard method to determine nematode densities relies on extraction of cysts from soil samples and their subsequent enumeration which is time-consuming. The method described in this article involves the extraction of nematodes obtained by a technique inducing the hatching of juveniles. Hatching of larvae is induced by incubation of the soil sample with “Acetox” followed by a Baermann funnel extraction. Instead of a visual estimation of nematode densities using a microscope, H. schachtii larvae are identified by a molecular diagnostic. The aim of this study is to distinguish between the three threshold infestation levels by comparing the intensities of PCR products derived from samples containing known numbers of target H. schachtii.     

The development of juveniles of Heterodera schachtii in roots of resistant and susceptible genotypes of Sinapis alba,Brassica napus,Raphanus sativus and hybrids

The development ofHeterodera schachtii Schm. (beet cyst nematode, BCN) juveniles in roots of resistant and susceptible genotypes belonging to cruciferous crop species and hybrids was studied from 4 to 28 days after inoculation. No difference in root penetration by larvae was observed between resistant and susceptible plants.The development of nematodes in roots from resistant plants ofRaphanus sativus L., resistant xBrassicoraphanus Sageret and a resistant hybrid xBrassicoraphanus x Brassica napus L. was similar. BCN resistance in these three sources of plant material appeared to be related to an increased male:female nematode ratio as compared to the ratio found in susceptibleR. sativus plants.Also in resistant plants ofSinapis alba L. and a resistant intergeneric hybridS. alba x B. napus the increase in male:female nematode ratio, as compared to the ratio found for susceptibleS. alba cultivars and a susceptible intergeneric hybridS. alba x B. napus, seemed to be related with the observed resistance. In roots of the resistantS. alba and of a resistant hybridS. alba x B. napus, however, BCN resistance might also be due to a slower development of larvae and increased necrosis of root cells at the site of larval penetration.     

The egg parasitoids ofThaumetopoea pityocampa in the atlas Mountains near Marrakech (Morocco)

Studies were performed on 25 egg batches ofThaumetopoea pityocampa (Den. & Schiff.) collected onPinus pinaster Ait. on 29. XI. 1995, in the Atlas Mountains of Morocco near Marrakech at 1400-1800 m above sea level. All the egg masses had been deposited in the autumn of 1995 and were exposed to the parasitoids throughout the developmental period of the host. In 1996, the egg batches, kept singly in test tubes, were observed almost daily. Emerged parasitoids were recorded and separated. The final analyses were made in November 1996 based on the meconia and remains of the emerged or the dead parasitoids in the eggs. In all cases, oviposition occurred from the base to the tip of the needles, distances varying up to 62 mm from the base. The mean number of eggs per batch was 175 (range 34-245), the number of egg-rows varied between 6 and 11, and a 1-cm egg-row contained a mean of 9 eggs. Caterpillars hatched from 72. 7% of the eggs; total mortality of the eggs was thus 27. 3%. The impact of egg parasitoids was 21. 4%. Most of the parasitized eggs were attacked byBaryscapus servadeii (Dom.) followed byOoencyrtus pityocampae (Mercet). Males (1. 5%) were found only in B. servadeii. The emergence rate ofO. pityocampae was much higher in the year of host oviposition than in the following year. B. servadeii emerged in equal numbers before and after hibernation, and in the subsequent year in equal numbers in spring and autumn. The high rate of emergence ofB. servadeii in April-May is discussed in relation to the embryonic development ofThaumetopoea bonjeani (Powel) until the end of winter, as an alternative host ofB. servadeii in the Atlas region.     

旱稻孢囊线虫（Heterodera elachista）孵化特性研究

为了解旱稻孢囊线虫的孵化特性,从水稻根系及根系附近土壤分离孢囊,在室内离体条件下研究不同温度及水稻根系分泌物、土壤浸液、水稻根汁等因子对2龄幼虫孵化的影响,并观察不同温度下2龄幼虫的存活能力.结果表明:旱稻孢囊线虫孵化的适宜温度范围为28～32℃,且在该温度范围初孵2龄幼虫的存活率高、存活时间相对较长,35℃下孵化率及初孵2龄幼虫的存活率、存活时间均明显下降,40℃下无线虫孵化,20℃下孢囊线虫孵化率仅为0.9％,4℃下可延长2龄幼虫的存活时间.水稻分泌物、水稻土壤浸液和水稻20倍根汁对旱稻孢囊线虫孵化具有刺激作用,5倍根汁和4 mmol/L氯化锌溶液对线虫的孵化有抑制作用.上述结果可为制定旱稻孢囊线虫防治措施提供依据.     

Defence responses ofArabidopsis thalianaduring invasion and feeding site induction by the plant–parasitic nematodeHeterodera glycines

The nature of local defence responses occurring during the infection ofArabidopsis thalianaby the soybean cyst nematodeHeterodera glycineswas analysed by light and electron microscopy.Arabidopsis thalianais not a regular host of this nematode, but invasion, feeding site induction and in rare cases development of juveniles was observed. Compared toHeterodera schachtii, which interacts compatibly withA. thaliana, the period of invasion and migration was prolonged. During migration a strong hypersensitive response, characterized by extensive necroses, browning, autofluorescence and cell wall depositions, occurred in cells that were not in direct contact with the nematodes. Cells selected as initial syncytial cells were pierced with the stylet and, after having passed a preparation phase, secretions were released. The cells responded with rapid vacuolation and deposition of callose-like material around the stylet and at the cell walls, and subsequent necrosis. In a very few cases the initial syncytial cells and neighbouring cells deposited callose-like material on their walls, but these cells remained intact so that functional syncytia developed, which allowed occasional nematode development.     

Effect of 4-chloro-2-methylphenoxyacetic acid and 2,4-dimethylphenol on human erythrocytes

The effects of exposure of human erythrocytes to different concentrations of 4-chloro-2-methylphenoxyacetic acid (MCPA) and its metabolite—2,4-dimethylphenol (2,4-DMP) were studied. The investigations concerned mainly the content of glutathione (GSH and GSSG), glutathione peroxidase (GSH-Px), glutathione transferase (GST), and the level of adenine energy charge (AEC). Reactive oxygen species (ROS) such as hydroxyl radical, superoxide anion, hydrogen peroxide, and nitric oxide are produced during normal processes in the cell. Under normal conditions, antioxidant systems of the cell minimize damage caused by ROS. When ROS generation increases to an extent that it overcomes the cellular antioxidant systems, the result is oxidative stress. We observed that MCPA and 2,4-DMP decreased the level of GSH in erythrocytes in comparison with control. MCPA did not affect glutathione peroxidase and glutathione transferase activity, while 2,4-DMP increased their activity. 2,4-DMP decreased the level of ATP and increased the content of ADP and AMP, leading to the fall of the level of AEC. MCPA and 2,4-DMP transform hemoglobin into methemoglobin, thus preventing oxygen transport. Comparison of the toxicity of MCPA and 2,4-DMP revealed that the most prominent changes occurred in human erythrocytes incubated with 2,4-DMP.     

Note: Transovarial activity of the chitin synthesis inhibitor novaluron on egg hatch and subsequent development of larvae ofTribolium castaneum

The effects of the chitin synthesis inhibitor (CSI) novaluron on egg hatch and on larval development ofTribolium castaneum (Herbst) concentrations of 1.0, 0.3, 0.2 or 0.1 ppm were tested. The effect of novaluron at low concentrations depended strongly on the exposure period. At 0.3 ppm, egg hatch ofT. castaneum was totally inhibited after 28 days; at 0.2 ppm the effect was much less but inhibition increased progressively to 66% in the 35-day experiment; at 0.1 ppm novaluron was ineffective. The viability of the larvae that hatched from the laid eggs and developed on untreated flour was also dependent on concentration of novaluron and exposure time: exposure ofT. castaneum adults to novaluron-treated flour at 0.3 ppm for 8 days, or at 0.2 ppm for 36 days, caused 100% or 97.5% mortality, respectively. At both 0.3 and 0.2 ppm, larval deaths were mainly in the first instar. Exposure ofT. castaneum adults to treated flour may serve as a good model for evaluating the effect of CSIs on internal feeders, especiallySitophilus oryzae (L.). The present study contributes to our understanding of CSI transovarial activity against internal stored product coleopterans whose larval stage develops inside the grain without contact with the toxicants. http://www.phytoparasitica.org posting Dec. 11, 2007.     

The effectiveness ofBacillus thuringiensis Berliner onBoarmia (Ascotis) Selenaria Schiff. (Lepidoptera,Geometridae) in laboratory tests and field trials

The effectiveness of a commercial preparation ofBacillus thuringiensis Berliner (Dipel) against eggs and larvae ofBoarmia (Ascotis) selenaria Schiff. of different age was examined in laboratory and in field tests. The mortality rate ofB. selenaria was proportional to the concentration ofB. thuringiensis and inversely related to the age of the treated larvae. In neonate larvae, 100% mortality was obtained even with a low concentration (0.5%). Egg hatch was not affected, but the survival rate of larvae hatched from treated eggs was very low (2.2%). No phytotoxicity of the commercial microbial preparation was observed on fruit or leaves of avocado. High doses ofB. thuringiensis persisted on avocados, probably because of specific conditions:i.e., absence of rainfall, moderate temperatures and limited penetration of sunlight. Tests carried out in large commercial orchards, using motor-guns and helicopters, yielded good results.     

五种药剂对黏虫卵的室内触杀效果及胚胎发育的影响

为有效防控黏虫Mythimna separata,选用灭多威、苦参·印楝素、苏云金芽胞杆菌Bacillus thuringiensis、甲维盐和高效氯氟氰菊酯5种药剂对其卵进行室内触杀试验,比较这5种药剂对黏虫卵和初孵幼虫的触杀效果及对卵的毒力,测定不同药剂处理后黏虫卵初孵幼虫存活率、发育历期、化蛹率、蛹重和羽化率;并通过冷冻切片技术观察不同药剂处理后黏虫卵的外部形态和胚胎发育情况。室内触杀试验结果表明,苦参·印楝素浓度大于0.1 mg/L时,对产后不同时间黏虫卵的校正死亡率介于42.89%～97.34%之间,苏云金芽胞杆菌浓度为0.01 mg/L时对产后72 h黏虫卵的校正死亡率已达71.99%;各浓度苦参·印楝素和苏云金芽胞杆菌处理产后24、48和72 h黏虫卵后,其初孵幼虫校正死亡率介于39.02%～83.59%之间。苦参·印楝素对产后24、48 h黏虫卵的毒力最大,致死中浓度LC_(50)分别为0.018、0.109 mg/L;苏云金芽胞杆菌对产后72 h黏虫卵的毒力最大,LC_(50)为0.004 mg/L。黏虫卵经5种药剂处理后,幼虫化蛹率、蛹重和羽化率分别介于91.07%～93.64%、0.272～0.284 g和86.60%～87.78%之间,与对照差异不显著,幼虫存活率较对照显著下降43.02%～60.27%,幼虫发育历期较对照延长0.23～0.88 d,其中灭多威、苦参·印楝素、苏云金芽胞杆菌处理的幼虫发育历期较对照显著延长。苦参·印楝素、苏云金芽胞杆菌使胚胎无法形成正常胚带,同时会使已发育的虫体出现蜷缩、腹部皱缩;高效氯氟氰菊酯会延缓胚胎发育时间,使已形成的虫体畸形或使其肠道断裂;甲维盐影响虫体对营养物质的吸收,造成虫体萎缩,使其不能正常孵化。在黏虫卵防治中推荐使用苏云金芽胞杆菌和苦参·印楝素。     

Management of the yellow beet cyst nematode with crop rotation,soil fumigation and granular nematicides

A trail field was managed for six years to test effects of short crop rotations, soil fumigation and granular nematicides on the population dynamics of the yellow beet cyst nematode (Heterodera trifolii f. sp.beta) and sugar-beet yields.In the two-year rotation, the cyst nematode population before planting varied from about the tolerance level (5 eggs per millilitre of soil) to 25 eggs per millitlitre of soil, leading to losses of sugar yield. Soil fumigation with metam-sodium effectively reduced the nematode density before planting, resulting in a 15 and 25% increase in sugar yield in the first two crops, respectively, but was insufficient to protect the third sugar-beet crop from yield-reducing nematode attack. This was attributed to the wet soil at the time of application and accelerated disappearence of the chemical in the soil through biological adaptation to repeated fumigation. Oxamyl or aldicarb granular nematicides applied as a side-dressing to the rows had insufficient effect to protect the sugar-beet from yield-reducing nematode attack. An overall treatment with aldicarb rotavated into the soil, alone and in addition to soil fumigation, increased sugar yield significantly. However in the two-year rotation, yield of the third sugar-beet crop treated with soil fumigation and granular nematicide was still lower than that of the untreated second crop in the three-year rotation.In the three-year rotation, thecyst nematode population before sugar-beet varied from hardly detectable to about the tolerance level. Here sugar-beet could be protected from yield-reducing nematode attack by soil fumigation or an overall treatment with granular nematicide. In the threeyear rotation with soil fumigation an increase ofRhizoctonia crown rot was observed in the second sugar-beet crop.Samenvatting Om de effecten na te gaan van korte rotaties, grondontsmetting en nematicide granulaten op het populatieverloop van de gele bietcystenematode (Heterodera trifolii f.sp.beta) en de opbrengsten van suikerbieten werd gedurende zes jaren een proef uitgevoerd op een natuurlijk besmet perceel van de proefboerderij Vredepeel.In de tweejarige rotatie variëerde de cystenematodepopulatie vóór het bietegewas boven de schadedrempel, wat resulteerde in verlaging van de suikeropbrengst. Grondontsmetting met metam-natrium veroorzaakte een effective vermindering van de dichtheid van de nematoden vóór de bieten en een verhoging van de suikeropbrengst van respectievelijk 15 en 25% bij de eerste twee gewassen, maar was onvoldeende om het derde bietegewas te beschermen tegen een opbrengst verminderende aantasting door nematoden. Dit was een gevolg van natte bodemomstandigheden bij het injecteren en het versneld verdwijenen van het middel door biologische adaptatie van de grond na herhaalde ontsmetting. Nematicide granulaten (oxamyl of aldicarb) naast de rij toegepast hadden onvoldoende effect om de bieten te beschermen tegen een opbrengstverminderende aantasting door nematoden. Een volvelds toepassing van in de grond gefreesde aldicarb alleen en toegevoegd na grondontsmetting verhoodge de suikeropbrengst beduidend. De opbrengst van het derde suikerbietegewas in de tweejarige rotatie was echter na toepassing van grondontsmetting en nematicide granulaten nog beduidend lager dan die van het onbehandelde tweede suikerbietegewas in de driejarige rotatie.In de driejarige rotatie variëerde de cystenematodepopulatie vóór het bietegewas van nauwelijks aantoonbaar tot nabij de tolerantiegrens. Hier kon het suikerbietegewas worden beschermd tegen een eventueel opbrengst verminderende nematodenaantasting door grondontsmetting of volveldstoepassing van nematicide granulaten.     

The influence of some agricultural practices on soil organisms and plant establishment of sugar beet

In a long term field experiment the influence of crop rotation and the application of insecticides and herbicides on soil arthropods (mesofauna), nematodes, soil fungi and weeds was investigated. Possible changes in numbers of not only pathogenic organisms, but also of predators or parasites of pathogens, could affect seedling establishment and/or yield of sugar beet. In soil samples taken during the spring, high population of the springtailOnychiurus armatus ware detected which caused considerable damage in the first two years. Later also rather severe infestations byAtomaria linearis occurred, probably caused by frequent sugar beet cropping.No significant influence of crop rotation on damage caused by soil arthropods could be detected yet, but in the 1/3 sugar beet and 2/3 winter wheat rotation more micro-arthropods and a higher diversity of species were found than in the blocks with continuous sugar beet growing. In the latter ones the numbers ofHeterodera schachtii increased and in 1980 the tolerance level was exceeded. On the contrary in the 1/3 sugar beet blocksPratylenchus spp. were dominant. Since a number of perennial weeds cannot be controlled sufficiently in sugar beet, some of them created a problem in the 1/1 sugar beet blocks.In the plots not treated with a soil herbicide large numbers of annual weeds provided alternative native food forO. armatus, which resulted in less plant damage. No significant effect of chloridazon on the micro-arthropod fauna could be detected. The insecticides lindane and aldicarb controlledO. armatus andA. linearis partially, and improved seedling emergence and to a lesser extent yield. Both insecticides had a variable effect on the relative abundancy ofCollembola and in addition lindane suppressed numbers ofAcariformes and aldicarb those ofParasitiformes. No negative influence on the species diversity could be detected. All effects did not last long and varied considerably from year to year.Indications were found that, if species ofCollembola, which could act as predators of nematodes, were suppressed, the numbers ofPratylenchus spp. andH. schachtii increased.Samenvatting In een veeljarig proefveld (1976–1979) werd de invloed van de vruchtopvolging en toepassing van insecticiden en herbiciden op bodemarthropoden (mesofauna), nematoden, bodemschimmels en onkruiden onderzocht. Niet alleen mogelijke veranderingen in de aantallen schadeverwekkers, maar ook in de aantallen predatoren en pathogenen van bodemplagen zouden het plantbestand en/of de opbrengst van suikerbieten kunnen beïnvloeden.Gedurende de eerste twee jaar van de proef werden in grondmonsters, die gedurende het voorjaar werden genomen, grote aantallen springstaarten (Onychiurus armatus) aangetroffen, die aanzienlijke schade veroorzaakten. Later kwamen eveneens aantastingen door het bietekevertje (Atomaria linearis) voor, waardoor in meerdere of mindere mate planten wegvielen.Er kon nog geen duidelijke invloed van de vruchtopvolging op de schade door bodemarthropoden worden vastgesteld, maar in de rotatie met 1/3 suikerbieten en 2/3 wintertarwe werden meer micro-arthropoden en een grotere soortenrijkdom gevonden dan in de gedeelten met een continuteelt van suikerbieten. In laatstgenoemde veldjes zijn de aantallen bietecystenaaltjes (Heterodera schachtii) toegenomen, waarbij in 1980 de tolerantiegrens werd overschreden. Daarentegen vond in de veldjes met 1/3 suikerbieten in de rotatie een sterkere vermeerdering vanPratylenchus spp. plaats dan in de continuteelt. Aangezien een aantal wortelonkruiden in suikerbieten niet voldoende kan worden bestreden, veroorzaakten enkele na enige jaren een probleem in de continue bietenteelt.In de veldjes die niet met een bodemherbicide waren behandeld vormden grote aantallen zaadonkruiden een alternatieve voedselbron voorOnychiurus armatus, wat een geringere aantasting van kiemplanten tot gevolg had. Er werd geen aantoonbaar effect van chloridazon op de micro-arthropoden vastgesteld.De insecticiden lindaan en aldicarb konden schade doorOnychiurus armatus enAtomaria linearis slechts gedeeltelijk voorkomen; er werd een duidelijk betere opkomst en soms ook een hogere opbrengst verkregen. Beide insecticiden hadden een wisselende invloed op de relatieve talrijkheid vanCollembola en bovendien onderdrukte lindaan de aantallenAcariformes en aldicarb deParasitiformes. Er kon geen negatieve invloed op de soortenrijkdom worden vastgesteld. Al deze effecten waren niet van langdurige aard en verschilden sterk van jaar to jaar.Er werden aanwijzingen gevonden dat, indien bepaalde soortenCollembola, die als predatoren van nematoden kunnen optreden, werden onderdrukt, de aantallenPratylenchus spp. enHeterodera schachtii toenamen.     

Untersuchungen zur Wirtseignung verschiedener geographischer Herkünfte von Ackerunkräutern gegenüber dem Rübenzystenälchen Heterodera schachtii Schmidt

Investigations on the suitability of weeds of various geographical origins as hosts of the sugar-beet nematode Heterodera schachtii Schmidt The suitability of five weed species of various geographical origins in Bavaria as host plants of Heterodera schachtii was tested. The root diffusates of all Capsella bursa-pastoris and Stellaria media origins examined increased hatching of larvae; Chenopodium album. Viola arvensis and Galium aparine did not have any effects. In biotests, cyst-forming was found regularly on the first-mentioned species, whereas only single ones were seen on the roots of Chenopodium album, in no case were new cysts found on those of Viola arvensis and Galium aparine. There were also no differences in influence on the population density. Hence, at least within a restricted geographical area, the suitability of weeds as hosts of Heterodera schachtii is species-specific.     

燕麦孢囊线虫在河北冬麦区的种群动态

为明确河北省燕麦孢囊线虫Heterodera avenae在自然环境下的侵染与发育特点,于2009-2012年分别采用漂浮法、浅盘法和酸性品红染色法在3个不同区域对土壤中孢囊和2龄幼虫(J2)以及根系内线虫进行了系统调查,并对孢囊内卵的发育动态进行检测.在土壤中除6月上中旬未检测到J2外,周年均分离到J2.冬前J2出现小高峰,种群密度为12.3 ～18.6条/100mL土样;在4月上中旬J2大量发生,种群密度为52 ～ 65条/100 mL土样.冬前J2侵入小麦后能够发育至3龄幼虫,3龄幼虫发生高峰在4月下旬至5月上旬,4龄幼虫的发生高峰在5月中下旬,白雌虫形成高峰期在5月下旬,且1年后孢囊内卵孵化率达到86.5％.研究表明,燕麦孢囊线虫在河北省小麦上1年发生1代,关键侵染期在3月下旬至4月中旬.     

Het koolcystenaaltje,heterodera cruciferae Franklin, 1945, in Nederland

Summary Heterodera cruciferae is found in the Netherlands in five different locations, living on cabbage, rape and rapeseed, whereas beets are not attacked. ThisHeterodera is distinguished from nearly all otherHeterodera's known in Europe by its small, red brown, roundish lemon-shaped cysts and its short, thick larvae(Fig. 1, 2, 3, 5). The only exception isHeterodera humuli, which has however a thinner cyst wall of a lighter colour with a conspicuous, coarse, irregular punctation and larva stylets with distinctly forward-pointing knobs (Fig. 7, 8). The males are redescribed; they have 5–7 lip annules and three teeth on each spiculum tip (Fig. 4). Population density and type of damage with culture of rape seem to be about the same as with beet sickness caused byH. schachtii (Fig. 6). In the most important cabbage areaH. schachtii plays a more important role thanH. cruciferae. With both eelworms, an advisory service based on soil sample examinations would probably be useful for the culture of cruciferous crops.     

Methods of assessing the efficacy of non-volatile nematicides

In-vivo tests of non-volatile nematicides using a fungal-feeding nematode Aphelenchus avenae were shown to be more reliable than in-vitro tests. Phoxim and carbofuran were as effective as thionazin against the stem nematode Ditylenchus dipsaci in preventing eggs being laid, but they did not prevent nematodes from migrating from treated plants. Aldicarb and phoxim delayed the emergence of second-stage juveniles from cysts of the potato cyst nematode Globodera rostochiensis; phoxim at 8 mg kg^?1 of soil gave the same results as aldicarb at 2 mg kg^?1 of soil and both chemicals altered the sex ratio in the final population. A simple pot-test with G. rostochiensis in foul soil types was used to demonstrate the comparative effectiveness of non-volatile nematicides.