An Integrated Approach in the Control of Potato Root Eelworm

During the last decade, new control possibilities for the potato root eelworm have come to the fore, namely resistant potato varieties and soil disinfection. These have led to an integrated approach to the control of the potato root eelworm in the Netherlands. For this purpose, a number of potato rotations, aiming at the prevention or elimination of non-detectable populations of the potato root eelworm, are prescribed for non-infested fields. These regulations allow the farmer to grow potatoes more frequently on non-infested soils if he uses control measures (i.e. resistant potato varieties, soil disinfection). More stringent restrictions are in force for infested fields on which the growing of susceptible crops and propagation material is, of course, prohibited.     

Een oriënterend onderzoek naar het voorkomen van en de schade veroorzaakt door het havercystenaaltje (Heterodera avenae = H. major) in 1955

Samenvatting Op vele bedrijven, waar een sterke rotatie van granen in het bouwplan is opgenomen, kan het havercystenaaltjes veelvuldig moeheidsverschijnselen in haver veroorzaken. Ook op bedrijven, waar dit gewas geen afwijkingen in de groei vertoont, komt het aaltje, zij het in geringe concentraties, algemeen voor. Tussen de besmettingsgraad van de grond en de schade aan het gewas bestaat een zeker verband. Dit verbank kan sterk beïnvloed worden door verschillende bijkomende factoren, waaronder de watervoorziening van der planten een belangrijke rol speelt.Het is nog niet duidelijk in hoeverre de techniek van het grondmonsteronderzoek gewijzigd dient te worden om te voorkomen, dat de levende inhoud van de cysten terugloopt.Summary The cereal root eelworm has become a serious pest in oats in some parts of the Netherlands, especially on light, sandy soils.In March and April 1955 1400 soil samples were collected from farms where the occurrence of the nematode was to be expected.In two different areas the degree of infestation was 78 and 96% of the total of fields under investigation. These figures indicate that the concerning farms were generally infested, but they do not represent the mean situation of the area.During the growing season each oat crop was examined for symptoms of the disease. The data collected were compared afterwards with the degree of infestation. There proved to be a positive correlation between the degree of infestation of the soil and the damage to the crop (tables 1 en 2). Several circumstances influence this correlation, among which the water supply of the plants seems to be a very important one.Cyst populations were identified by morphological characters to separate them from the clover root eelworm,Heterodera trifolii (Goffart, 1936), which was also present in 6,5% of the samples in one, and in 32% of the samples in the other area.The larvae in the cysts ofH. avenae evidently do not stand dry preservation, which is in accordance with recent experience in England (2).Dry preservation inplastic cavity slides for 1–3 weeks resulted in a decrease of viable cysts and larvae of 52%. A more suitable technique for collecting and handlingH. avenae in studied for further work.Het onderzoek werd verricht in samenwerking met de Rijkslandbouwconsulenten te Zutfen en Horst (L.) en het kantoor van de Plantenziektekundige Dienst te Doetinchem.     

Distribution of Potato Cyst Eelworm in Scotland1

Although potato cyst eelworm has been known in Scotland for more than 60 years, infestations are fewer than might have been expected. In 22 years of soil testing, based on nominal 500 g samples and sampling units of up to 6 ha, 80% of the farms examined were found free from detectable infestation and 10%, i.e. half the infested farms, had one infestation only. Most populations were light; one third of all infested samples contained a single viable cyst and 80%, ten cysts or fewer. It is suggested that long rotations have kept eelworm populations in check over much of the country, but in some areas their effectiveness has been reduced by persistent groundkeepers. Surveys indicate that Heterodera pallida Stone is uncommon and so the progressive use of resistant varieties, which are proving popular with seed growers for their commercial qualities, coupled with the long rotations generally practised, may well tip the balance even more favourably towards increased control.     

Fluctuations in Sunn-pest Populations in South-eastern Anatolia

Sunn pest ( Eurygaster integriceps ) is the most serious and widespread pest of cereals in south-eastern Turkey. It is very important to estimate its spring populations, and the area possibly needing to be treated, a few months before they migrate to the fields. The field populations of the pest and the severity of epidemics can be forecast from the population density of overwintering adults per plant in the overwintering localities. To do this, surveys have been made since 1955 on 25 selected mountain sites. Parallel to these investigations, the population of overwintered adults per m2 in cereal fields has been determined in order to fix the area to be treated, since 1956. A relation can be seen between the population density of overwintered adults per plant and the next season's populations in the infested areas.     

Surveys of beet cyst nematode in England 1977–80

Surveys of sugar beet crops for beet cyst nematode ( Heterodera schachtii Schmidt) in seven selected areas of England have provided data on distribution of the pest and on some factors affecting its occurrence. These data were mapped by CAMGRID computer program.
Infestations occurred mostly on the East Anglian fenland (14% of fields infested) and in this area were more frequent nearer the sugar beet processing factory. In the remaining areas the few infested fields (5% or less) were generally scattered but a small concentration of infestation occurred in the West Midlands in an area of intensive horticulture with frequent brassica crops. The survey data did not support the view that beet cyst nematode infestations occur more frequently near access points to the crop. In the surveyed areas frequency of host crops appears to be more important than soil type in determining the likelihood of infestation.     

THE EFFECT OF COMPETITION FROM CEREAL CROPS ON THE GERMINATION AND GROWTH OF AVENA FATUA L. IN A NATURALLY-INFESTED FIELD

Summary. The effect of winter wheat, winter rye, winter barley, spring barley, and fallow cultivated as for a winter cereal, on germination and growth of wild oats ( A. fatua ) was investigated on a naturally-infested field. Treatments were continued for 2 years on the same plots and in the third year all plots were cropped with spring barley. Wild oats were not allowed to shed seeds.
A. fatua was controlled by a dense crop of an autumn-sown cereal. The crop genus was unimportant provided it grew well on the site; its effectiveness depended on its density when the wild oats germinated in spring. Winter wheat and winter rye were equally effective. Even in a light crop of barley, wild oats grew much less vigorously than on the fallow plots. Beyond a certain crop density dependent on soil fertility, further increase in crop did not decrease the size of wild oats. The heaviest crop did not completely suppress the wild oats.
The crop affected the wild oats mainly by decreasing growth of the seedlings, but under winter wheat and winter rye some wild oat seeds may have remained dormant, germinating in the spring barley in the third year, perhaps because the crops decreased the soil moisture content. Nitrogenous fertilizer increased the weight of both crops and wild oats. Barley was more severely affected by soil acidity than wild oats and on acid areas of barley plots the wild oats were larger than where the pH was higher. In wheat and rye which were scarcely affected by soil acidity the size of the wild oat plants was unaffected by soil pH.
L'effet du competition des céréales sur la germination et le développement d' Avena fatua dans un champ naturellement infesté .     

基于GIS的小麦孢囊线虫病在江苏省的发生分布与群体密度分析

 2009-2011年间对江苏省12地1市共59个区县市290个乡镇的小麦孢囊线虫病发生情况进行了系统调查,并结合GIS软件,绘制了该病害的发生分布、群体密度及其与土壤质地之间关系的地理信息矢量图。调查结果表明： 在580个调查点中,有47个区市县152个乡镇的301个调查点发现CCN;在苏北的徐州地区、苏中的泰州和扬州地区以及苏南的镇江地区CCN发生较为普遍,而江苏其他地区发生率相对较低。不同地区平均CCN群体密度差异较大, 徐州、扬州和泰州地区样品分别为34.4、17.5和17.1个孢囊/100 mL土,而连云港、南通和苏州等地区仅为3~5个孢囊/100 mL土;ArcGIS矢量图显示江苏省小麦孢囊线虫病发病田的孢囊群体密度与土壤质地有密切的关系,在土壤质地为沙土和沙壤土的发病田孢囊群体密度普遍较高,徐州沛县王店镇的CCN样品孢囊群体密度最高达到了191.0个/100 mL土,而土壤质地为粘土的病田小麦孢囊线虫群体密度相对较低。本研究为宏观了解小麦孢囊线虫病在江苏省的发生情况和监测发病重灾区CCN的田间发生动态规律提供参考, 并为今后的病害综合防控技术示范与推广提供理论依据。     

Waarnemingen betreffende Ditylenchus radicicola (Greeff, 1872) Filipjev, 1936

Summary On account of recent records ofDitylenchus radicicola (Greeff, 1872)Filipjev, 1936 in Dutch meadows, a study was made of its biology. Literature data were summarized.The eelworm attacks the roots of Gramineae and causes spiralshaped galls, which may contain up to 60 adults and some thousands of eggs and larvae each. Young larvae may actively hatch in water from whole, undecayed galls at temperatures around 17°C (Graph. 1). Root exudate of host plants did not stimulate the hatching process. The first larval stage is infective and may penetrate young root tips and also young galls (Fig. 1); it can withstand 2 month desiccation and also desinfection in a solution of an organic mercury compound. The host plant influences the number and size of the root galls (Graph. 2). Fig. 2 shows the anatomy of a young gall.The parasite is only found in grasses in this country and damage has not yet been found. Rye, wheat, barley and oats proved to be susceptible in inoculation trials; 17 plant species have been mentioned as natural hosts in different countries now and 3 are only found susceptible in inoculation trials.     

Spread of proso millet (Panicum miliaceum L.) in Ontario, Canada. I. Rate of spread and crop susceptibility

The infestations of two biotypes of Panicum miliaceum L. were monitored over a 5-year period (1981–1985) as they occurred in two townships in southwestern Ontario, Canada. On average, 16·5% of the cultivated fields in Hullett township were infested with the black-seeded biotype while 12·9% of the fields in North Norwich township were infested with the golden-seeded biotype. Neither population showed clear signs of increasing. The two biotypes were similar in their ability to persist as adult infestations. The black-seeded biotype showed a greater potential for colonizing uninfested fields. The crops grown in this region showed different susceptibilities to infestation by P. miliaceum. Corn (maize) fields were susceptible while most grain fields were resistant to infestation. White beans were susceptible to infestation by the black-seeded biotype. Wheat and oat crops were more resistant to infestation by the golden-seeded biotype than to those of the black-seeded biotype.     

Changes in the incidence of ragwort (Senecio jacobaea L.) infestation of grassland over a 4-year period in NE Scotland

A roadside survey of 4749 fields in eight areas of NE Scotland was conducted annually from 1979 to 1982. The proportion of grass fields infested with ragwort remained steady at 18–19% from 1979 to 1981 but fell to 13·5% in 1982. This fall resulted from fewer fields becoming newly infested and from more fields that had remained in grass ceasing to be infested. The proportion of infested fields remaining in grass that showed a reduction of two or more points on a 0–5 logarithmic scale of ragwort density (a possible indication of the frequency of control measures) was 24·0% in 1979–1980, 21·7% in 1980–1981 and 36·3% in 1981–1982. The incidence of ragwort infestation was consistently higher in some areas than in others and was not related to the proportion of arable crops. The change in incidence of infestation varied greatly between different areas, as did the proportion of infested fields whose score on the 0–5 scale fell by two or more points. In 1979–1980 and 1980–1981 this proportion had to exceed 22% to effect a net decrease in the incidence of infestation in an area, but in 1981–1982 no relationship was evident between these two measures of change. The incidence of infestation in all areas increased with increasing sward age but one area (Moray and Nairn) had a much higher proportion of young grass infested than any of the others. Over 99% of ragwort infestations consisted of Senecio jacobaea, infestations of S. aquatints Huds. being rare.     

On biotypes of the cereal-root eelworm (Heterodera Avenae) and resistance in oats and barley

In the Netherlands four biotypes of cereal-root eelworm have been recognized by usingAndersen's series of test varieties. Three forms ofAvena sterilis and 14 varieties of oats were found to be resistant to the four biotypes. In barley two varieties showed resistance to four biotypes and many varieties were found to be resistant to one, two or three biotypes.     

A STUDY OF THE COMPETITION BETWEEN BARLEY AND OATS AS INFLUENCED BY BARLEY SEEDRATE, NITROGEN LEVEL AND BARBAN TREATMENT

Summary. The object of the work described in this paper was to obtain information on the relationship between the effects of crop competition and barban treatment on oats growing in another cereal. The work was carried out on barley cross-drilled with cultivated oats. Variation in crop competition was obtained by using different barley seed-rates and nitrogen levels. Increasing the seedrate of barley without applying barban resulted in a reduction of the initial oat population. This reduction applied to weight of individual shoots, number of shoots and panicles per unit area and number of spikelets per panicle. The application of barban at selective rates gave an independent reduction of oats of the order of 80%. This value proved almost constant at each seedrate of barley. Crop competition and barban accordingly seem to art independently and their effects appear to be simply additive. The barley fresh weights per unit area increased substantially when oat competition was reduced by barban treatment. The highest increase occurred on the plots with the lowest barley seedrate in spite of the fact that these plots still appeared infested with oats at harvest time. Nitrogen application stimulated the growth of barley and oats to a similar degree and did not in consequence lead to a selective suppression of oats.
Etude de l'influence de la densité du Semis, du taux de fertilisation azotée et du traitement au barbane, sur la concurrence entre une Orge et une Avoine     

转基因抗虫植物对天敌昆虫的影响

迄今对16种捕食性和7种寄生性天敌昆虫个体进行的毒性测定表明，转基因植物对天敌昆虫没有直接毒性；取食了转基因植物的猎物对大部分捕食性天敌昆虫个体无毒副作用。取食了转基因植物的寄主害虫如表现亚致死反应，则对寄生蜂个体无毒副作用，甚至对寄生蜂与抗虫作物间有增效作用；如寄主表现致死反应，则对寄生蜂个体有明显毒副作用。转Bt基因棉花，玉米和马铃薯田中主要广谱捕食性天敌种群数量等于或显著高于常规田，生测中对普通草蛉的副作用并未使其大田种群受到不良的影响；寄生性天敌昆虫种群数量除在个别Bt棉田中明显减少外，在其他Bt作物田中均等于或高于常见田，除个别棉田外，未发现Bt作物田中天敌群落受到不良影响，部分研究发现Bt作物田中某些非靶标刺吸口器害虫上升为主要害虫，数量明显高于常规田，建议采用“三层次检测体系”评价转基因作物对天敌昆虫的影响。     

Specificity oflongidorus cohni as a pathogen of oats

In a host study of the ectoparasitic nematodeLongidorus cohni, involving six field crops, only oats were found to afford rapid nematode population build-up and to suffer severe damage. No increase in nematode population, plant damage or root symptoms was observed on wheat, barley, purple vetch, field pea or berseem clover.     

Invasive weed facilitates incidence of Colorado potato beetle on potato crop

We examined whether the invasive silverleaf nightshade, Solanum elaeagnifolium (Cavanilles) can facilitate the infestation of potato (Solanum tuberosum (L.)) by the Colorado Potato Beetle, CPB, Leptinotarsa decemlineata (Say) in Greece, which would have important financial and pest management implications for the growing of potato crops. In laboratory tests, CPB from Lesvos could utilise S. elaeagnifolium if supplied with whole plants. In the field, however, CPB was only found on S. elaeagnifolium after the start of the spring potato harvest and the resulting loss of potato foliage, and no eggs were laid. This suggests that S. elaeagnifolium provides only a temporary food resource for adult beetles. One of 10 surveyed summer potato fields near the study population of S. elaeagnifolium was infested with CPB. It is likely that the presence of S. elaeagnifolium in the vicinity of spring and summer potato fields can help maintain CPB population viability in the immediate post harvest period of the spring potato crop, which may in turn facilitate the infestation of summer potato fields with CPB.     

Meloidogyne chitwoodi and Meloidogyne fallax in France: initial management experiences

Since 2008, the French NPPO has been controlling two outbreaks of Meloidogyne chitwoodi and Meloidogyne fallax, in Picardie (open fields) and in Bretagne (glasshouses). Intensive investigations have been undertaken to delimit these outbreaks and to help formulate the best control management strategy to adopt in these two very different situations. In open fields, eradication measures have been implemented, with bare fallow in infested fields being adopted as the main measure, despite the impact on affected growers and high financial cost. Recently, soil analyses in fields after 2 years of bare fallow showed that neither M. chitwoodi nor M. fallax was detected in 99% of cases, and measures have now been reduced: crops such as cereals are now allowed in these fields, but no tubers or root crops can be grown. Under glasshouses, eradication was not considered feasible and so a containment strategy was followed. An extensive national survey of susceptible crops has also been carried out for early detection of possible new outbreaks.     

云南草地贪夜蛾冬春季虫源分布及其主要影响因素分析

云南是我国草地贪夜蛾Spodoptera frugiperda主要降落区、周年繁殖区和北迁南回的重要通道。本研究基于室内生物学测定和全省气象数据, 并通过田间实地调查, 对冬春季虫源分布区及其主要影响因素进行了分析。结果表明:1)云南全省129个县/区/市中有45个县/区/市为草地贪夜蛾的周年繁殖适宜区, 有64个县/区/市为幼虫冬春季发生区。周年繁殖适宜区和幼虫冬春季发生区主要分布在25°N以南的西部、西南部、南部和东南部区大部区域, 以及西部怒江和北部金沙江沿岸部分地区。2)云南东西部草地贪夜蛾的发生程度和种群数量存在明显差异, 具有典型的区域特点:西部至南部普遍发生, 种群数量高, 为害严重, 有虫田率超过90%, 平均受害株率为30%~59%, 平均百株虫量为20~47头; 东南局部区域发生轻, 平均被害株率13.01%, 百株虫量12头; 中部及以北地区除河谷热区外, 冬春季未见有草地贪夜蛾为害。调查结果与虫源分布区预测结果重合度较高。3)玉米种植分布和生育期对草地贪夜蛾的发生有直接影响, 同时, 用药水平及种植模式与草地贪夜蛾的发生程度关系密切。研究结果对草地贪夜蛾种群监测与预警有指导作用。     

Effects of crop rotation and removal of crop debris on the soil population of two isolates of Verticillium dahliae

Microsclerotia of Verticillium dahliae are produced in large numbers on senescing parts of host plants and remain viable in the soil for many years. Changes in the population density, i.e. density of microsclerotia, in the soil were measured in micro-plots using two isolates of V. dahtiae , specific to either field bean or potato, several crop sequences comprising potato, field beans and barley, and either the removal of aerial debris of the crops or incorporation into soil.
Potato was more susceptible to the potato isolate and field bean more susceptible to the field bean isolate. Removal of debris of potato and field bean reduced numbers of microsclerotia in the soil in the subsequent years, but removal of barley straw had no effect. Initially non-infested control micro-plots became infested, probably by the growth of potato roots into the naturally infested subsoil. The rate of increase of the microsclerotial population in the non-infested control micro-plots was larger than in the initially infested treatments, because more colonized debris was produced. It is concluded that removal of aerial debris of host crops is important to reduce the soil population of V. dahtiae.     

Population Dynamics of <Emphasis Type="Italic">Monosporascus</Emphasis><Emphasis Type="Italic">cannonballus</Emphasis> Ascospores in Marsh Soils in Eastern Spain

The population dynamics of Monosporascus cannonballus ascospores in the soils of four muskmelon fields located in a marsh area in Castellón province (eastern Spain) was studied for a 3 year period. Two of these fields were cropped to muskmelon with fallow periods between muskmelon cropping, and the others were in fallow and had extensive flooding periods. Muskmelon cultivation resulted in a progressive increase of the number of ascospores in soil, reaching a maximum 7 months after muskmelon planting (2–4 months after plant death), and a subsequent decline during fallow periods between muskmelon crops. During muskmelon cropping, in-bed and between-bed ascospore numbers were compared and, in general, there were no statistical differences between them. In the fields which were in fallow and flooded, the dynamics found was a progressive decline of the population of ascospores. Soilborne inoculum was viable and capable of infecting muskmelon at the end of the 3 year period in all fields, demonstrating that ascospores of M.␣cannonballus are able to survive for this period of time in the absence of muskmelon cultivation and also that this fungus seems to be well adapted to survive in soils which maintain a high water table during the crop or under flooding conditions.     

Crop Rotation and Soil Pathogens — Trends in Germany

The need to cut costs has led to a simplification of crop rotation in several fields of plant cultivation. The results of Thormann, who has grown wheat continuously on parts of his farmland for 10 years, are discussed. Also, the preliminary results of our own experiments with increasing proportions of wheat and barley suggest that more wheat and barley may be cultivated in crop rotation than is allowed according to the conventional limits determined by the increase of foot rot diseases and cereal root eelworm. Even in successive crops of maize the problem of soil-borne pathogens can be tackled: the spread of blister smut is stopped by the control of the frit fly and by selection of tolerant varieties; root and stem rots of maize are overcome by the selection of appropriate varieties, too. On the contrary, the potato root eelworm is a serious pest in all sites of intensive potato production. Only an integrated control including the use of resistant varieties and the application of nematicides gives success. Much research work has to be done mainly to get more information on the biotical defence mechanisms of the soil.