Besteht das Risiko der Verschleppung der Bakteriellen Ringfäule der Kartoffel durch den Krautschläger?

In 2001 and 2002, two field trials were performed by the Plant Protection Service (PPS) of the Landwirtschaftskammer Weser-Ems in Oldenburg and the Institute for Plant Protection of the Bavarian State Research Center for Agriculture (LfL) in Freising respectively to examine the transmission of the bacterial ring rot pathogen of potato (Clavibacter michiganensis ssp. sepedonicus) by haulm cutting. In the experiment conducted by the PPS in Oldenburg a lawn-trimmer was used to simulate haulm cutting, before a bacterial suspension was sprayed on the ends of the cut haulms. Two cultivars (early and late) were tested and also the effect of an additional chemical measure for haulm destruction on the transmission of the pathogen was determined. In the trial performed at the LfL in Freising plots with infected plants for the contamination of the haulm cutter were treated immediately prior to plots with healthy plants. Infections of stems (re-growth) and tubers of the plants were determined by polymerase chain reaction (PCR) and indirect immunofluorescence antibody staining (IFAS). In the trials conducted with the haulm cutter, ring rot could be detected in the re-growth of 60% of the plants derived from healthy tubers 4 weeks after haulm cutting. It was confirmed in a bioassay, that the isolated pathogens were viable and virulent. Although the ring rot pathogen was transmitted to a great extent to the leaf material, no infection of progeny tubers occurred in a total of 450 tested plants. However in general a migration of the transmitted pathogen to the tubers cannot be excluded. Therefore further on it is advisable to clean and disinfect the haulm cutter before each use.     

Novel approaches to integrated pest and disease control in glasshouse vegetables in the Netherlands

As a result of government policy and consumers' attitudes to environmentally compatible growing systems, research is focused on reduction of pesticide input into the environment. This aim is approached in different ways. With so-called “closed growing systems”, soil fumigants are no longer needed, resulting in an estimated 60% reduction in the total use of pesticides. Further, far smaller quantities of (systemic) pesticides need to be added to plants, via the nutrient solution, than with soil-grown crops. Water disinfestation is essential to minimize the spread of diseases and heat treatment and ozonization are already used under commercial conditions. Filtration appears to be neither reliable nor practical. Other disinfestation methods are under investigation. Ventilators may be provided with insect-proof screens to minimize infection pressure, especially on young plant material. Air filters in combination with mechanical ventilation may be an option for the future to raise healthy plants. A further reduction in the use of pesticides can be achieved by developing biological and integrated control of insects and fungi. Simultaneous application of several biocontrol methods in the fruit vegetable area has increased the complexity of IPM. Open rearing systems of parasitoids on alternative hosts to control cotton aphids and leaf miners are promising. IPM is highly dependent on the availability of selective chemicals. Biological control of root-infecting fungi in substrate crops shows promise. Integrated control of powdery mildew in cucumbers using a combination of nutritional and climatic management and varieties showing partial resistance will be studied. Improvement of application techniques for pesticides is being studied by plant pathologists in cooperation with technical experts. The aim is to reduce pesticide application rates, to minimize losses to the environment and to avoid health risks for the worker. By developing decision-support systems for crop protection, optimal use of beneficial insects is achieved and unnecessary applications of chemicals are avoided. A programme to develop such a system for the sweet pepper crop is under way.     

Looftrekken of doodspuiten van aardappelen

Summary In Holland the haulm of seed potatoes of many varieties is removed in time to prevent virus infection by aphids. In the last few years pulling the haulm by hand has been partly replaced by killing the haulm with chemicals.The relative effect of these two methods upon the number of tubers subsequently diseased byPhytophthora infestans has been studied in a field experiment. In the plots where the haulm was pulled by hand, twice as many diseased tubers occurred, as in the plots where it was killed with sodiumarsenite.     

The role of soil, seed-potato tuber and haulm in the transmission of Phoma foveata from infected seed to daughter tubers

Infestation of ridge soil by Phoma foveata was examined over 4 years by collecting soil samples at various distances from seed tubers which were either naturally infected or inoculated with a distinctive strain. Samples were taken on four occasions during each growing season. Infestation was greatest immediately around the tuber and was largely confined to a distance of 15 cm until haulm destruction, after which P. foveata was detected more widely in the soil.
The effects of various seed-tuber and haulm treatments on the incidence of daughter-tuber contamination by P. foveata were assessed over 5 years. Removing the infected seed tuber at emergence significantly (P < 0.05) reduced the contamination at haulm destruction of daughter tubers harvested by hand in only 1 out of 4years. In all years, tuber contamination was much less(P < 0.05) when stems were pulled and removed than when they were desiccated by applying diquat dibromide. The incidence of tuber contamination did not increase between haulm destruction and harvest when stems were pulled and removed. In another experiment, tuber contamination increased linearly with the delay in pulling haulms after applying diquat dibromide. Cutting and removal of stems tended to reduce gangrene contamination, relative to the desiccation of stems by applying diquat dibromide, in all years where the seed tuber had been removed, but in only 2 out of 5 years where the tuber was present.     

Formation of sclerotia by Rhizoctonia solani on artificial media and potato tubers

Independent of the nutrient medium and the size of Petri dish, sclerotium initials ofRhizoctonia solani AG-3 appeared after a fixed period of time. The same held for the completion of maturation of the sclerotia. Deprivation or extra supply of nutrients reduced or increased, respectively, final mass of sclerotia but did not affect the moment of initiation and of maturation. Transfer of a mycelial mat from water agar to a nutrient-rich medium caused the formation of black solid sclerotia within four days all over the mat and not only around the site of inoculation as usually occurs on rich medium. Final sclerotial mass was higher on liquid medium than on agar. The results indicate that formation of these sclerotia is not associated with cessation of linear hyphal growth or with starvation. On mature tubers, sclerotia and hyphae are spread over the whole surface. On young growing tubers sclerotia are rarely found in the immediate vicinity of lenticels. This suggests a release of inhibitory factors at these sites which diminishes during tuber maturation. Volatile exudates from underground plant parts seem to further promote the sclerotium formation. On all underground plant parts, even the roots, final sclerotial mass was higher after wounding. After haulm destruction, development of black scurf was not stimulated by a short-term trigger or by roughning of tuber surface. The observations rather suggest that the stimulation results from an increased tuber exudation of stimulatory nutrients, water and stress factors and also from a reduction of as yet unknown inhibitory factors. Results indicated that in infested soils, the estimated inoculum density at the day of haulm destruction has no predictive value for black scurf development.     

Experience of Ring Rot Caused by Corynebacterium sepedonicum(Spieck. et Kotth.) Skapt. et Burkh. in Sweden. Particularly Detection of the Disease in its Latent Form)1

As it is difficult to detect ring rot in its latent form as well as in badly decayed tubers and in potato haulm, a diagnostic technique has been developed. With the help of a Turmix blender and a little water, a suspension is made of the suspected material. The suspension is inoculated into eggplants. Gram-staining of bacteria in sap from petioles of leaves showing symptoms is used to confirm the diagnosis. Some results obtained with this method applied on potatoes and potato haulm are described.     

Investigations on the effect of haulm destruction and additional root cutting on black scurf on potato tubers

In greenhouse experiments factors which are involved in the stimulation of sclerotia formation byRhizoctonia solani Kühn on potato tubers after haulm destruction were investigated. Cutting off the shoot stimulated the production of sclerotia as much as chemical haulm destruction. This was also observed when potato tubers were grown away from the roots in a separate compartment filled with steamed perlite. Fewer sclerotia were produced when roots were cut in addition to haulm destruction compared to haulm destruction alone. Cutting off the roots alone often stimulated sclerotia production. The data indicate that sclerotia production was directly affected by the tuber and probably due to physiological changes in the tuber caused by elimination of the shoot.Samenvatting In kasproeven werd onderzocht welke factoren betrokken zijn bij de stimulering van de produktie van sclerotiën op aardappel doorRhizoctonia solani Kühn als gevolg van loofvernietiging. Afknippen van het loof stimuleerde de vorming van sclerotiën evenzeer als chemische vernietiging. Na afknippen van het loof trad de stimulering ook op bij knollen, die zich ruimtelijk gescheiden van de wortels in gestoomd vochtig perliet konden ontwikkelen. Doodspuiten plus doorsnijden van de wortels resulteerde in minder lakschurft dan doodspuiten alleen. Wanneer alleen de wortels werden doorgesneden resulteerde dat vaak in meer lakschurft. De vorming van sclerotiën wordt dus direct door de knol beïnvloed. Dit effect lijkt voort te komen uit fysiologische veranderingen in de knol.     

Extended summaries SCI pesticides group symposium resistance '91

The Dutch government has a coherent, long-term policy regarding attainment of a sustainable development affecting agriculture and horticulture, the requirements of which are very strict and will be difficult to satisfy. The growers of protected crops try to meet these requirements by developing so-called closed growing systems. Two other approaches in the policy are a substantial reduction of the volume of pesticides used and a very critical evaluation of the pesticides permitted. In this governmental policy, Integrated Pest Management has shown prospects in horticulture; it will play a very important role in the near future but is now considered as part of the broader concept of Integrated Production Systems. The glasshouse industry is very actively developing its own strategy to satisfy government targets and market demands for high-quality products produced by environmentally safe methods. The vegetable auctions have developed a policy of environmentally conscious production which should put the vegetable industry into a strong marketing position for its produce.     

Some Aspects of New Technology for Protection of Field Crops in Poland (Machinery and Techniques)1

The Institute for Plant Protection at Poznan (Poland) examines the biological efficacy of new plant protection equipment or techniques. Examples of recent studies include: 1) a sprayer with a lateral reach of up to 40 m under favourable conditions, which has been successfully used on crops liable to mechanical damage from traditional tractor sprayers (oilseed rape at flowering, field bean, seed crops of sugar beet and onion, sunflower, maize); 2)equipment for spraying potatoes against Thanatephorus cucumeris at the time of planting; 3) use of passage-ways for sprayers in cereal crops, results having shown that spraying from passage-ways gives better biological results and that adjoining plants compensate the losses due to absence of plants in the passage-ways.     

Measurement of healthy and diseased haulm area for assessing late blight epidemics in potatoes

The advantages of assessing disease severity by visual grading and by measuring healthy and diseased plant area were compared in four mild to moderate late blight epidemics during spring and in two severe epidemics during autumn in Israel. Disease progress curves obtained through visual grading showed a continuous increase, but the area of lesions tended to fluctuate during the cropping season and often reached a maximum in plots in which the total amount of foliage was also largest. The healthy haulm area differed with disease intensity and undefined seasonal and cultural influences. The decrease in healthy haulm area was not related to expansion of the blighted area only, but also to the breaking of plants at stem lesions. This phenomenon was especially evident in the warm spring season and was not determined by visual grading of disease severity. Each kind of assessment revealed different features of the epidemics and suited different applications. Visual grading enabled the easiest comparison of epidemic patterns. Lesion areas reflected patterns of inoculum potential, while healthy haulm areas reflected the integrated influences of factors affecting the crop and disease and thus provided useful data for simulating epidemics and for estimating yield losses.     

THE INFLUENCE OF ENVIRONMENT ON POTATO HAULM KILL BY DIQUAT AND ON ITS RESIDUES IN THE TUBERS

Summary. The effect of various environments on the degree of desiccation and of residues in King Edward and Majestic potatoes was studied. The higher residues frequently associated with the variety King Edward are ascribed from glasshouse experiments to greater diquat movement; they could not be accounted for by differences in uptake between the two varieties.
In glasshouse experiments, uptake was increased both by high air humidities and reduced light intensities before and after treatment. Since earlier work with cocksfoot and wheat indicated that dry soil conditions markedly increased movement, it is concluded that dull, humid air conditions associated with dry soil would be most conducive to efficient haulm desiccation and also to highest residues in the tubers. Late afternoon or evening treatment often provides thes conditions, and residues were in fact least from morning treatment.
In the field, increases in haulm desiccation were associated with reductions in residues. As they were observed only at light intensities below 5000 lux, they are unlikely to occur in normal dull weather.
Rain falling soon after spraying did not reduce the extent of haulm desiccation or diquat residues.
Influence de I'enviromurtunt sur la destruction des fanes de pomme de terre par le diquat el sur ses     

Plant Protection and Production in Modern Society1

Many currently existing agricultural production techniques have been developed in total reliance on effective chemical pest control. Today, however, it is becoming clear that chemical pest control has a number of limitations, and its ever increasing costs may well make it a limiting factor in agricultural production. This has already occurred in a number of cotton growing areas. The need for increased world food production will require improved pest control methods. If no special precautions are taken, we will undoubtedly end up in many other crops with a situation similar to that of cotton. In view of the reduced availability of new pesticides, those currently available should be used in the optimal way. At the present time, the integrated pest control approach is the best means of accomplishing this. The introduction of such programs will require official support through legislation or technical assistance. In the future, various new developments in pest control are to be expected. Greater reliance will be placed on the use of computer science. Further effort will be needed in areas such as crop loss assessment, stored product pests, technical assistance to farmers and pesticide selectivity. Closer international collaboration on plant quarantine matters and pesticide registration are essential for the future of pest control.     

Development of symptoms caused by Erwinia carotovora ssp. atroseptica under field conditions and their effects on the yield of individual potato plants

Infection of seed tubers by pectinolytic Erwinia species can lead to the development of various symptoms during vegetative growth of potato crops, including non-emergence of plants, chlorosis, wilting, haulm desiccation and typical blackleg. The relationships between types of symptoms and yield are poorly documented, and are investigated by following the development of symptoms in potato plants grown under field conditions from seed tubers artificially inoculated with E. carotovora ssp. atroseptica ( Eca ) , and measuring the yield of each plant. Symptoms were classified into five main types (non-emergence, wilting/chlorosis, blackleg, haulm desiccation and plant death). Each plant was scored for types of symptom on four successive dates; plants without visible symptoms were scored as healthy. The method of inoculation and inoculum concentration proved major factors for the subsequent development of symptoms. Disease development was more severe after vacuum infiltration of bacteria into seed tubers than after shaking tubers in contaminated sand. Disease usually progressed from chlorosis and/or wilting to partial or total desiccation on a given plant. Yield losses varied according to symptom type, but the relationship between symptoms recorded and yield also depended on scoring dates. The data suggest that the beginning of tuber growth might be the most suitable stage for predicting yield losses from symptom observations. In both cultivars studied (Bintje, highly susceptible, and Désirée, moderately resistant), the yield of symptomless plants growing from inoculated seed tubers was significantly less than that of control plants, indicating that the presence of bacteria on the seed tuber was detrimental, even in the absence of visible symptoms. Differences in symptom expression in the field between cultivars matched the level of visible infection of tubers at harvest, as Bintje tubers showed a higher incidence of rot than Désirée tubers.     

Regulatory problems associated with natural products and biopesticides

For registration, the United States Environmental Protection Agency (USEPA) separates pesticides into conventional chemical pesticides and biochemical and microbial pesticides. Natural products generally fall into the latter category. The USEPA has specified the test requirements for registration in the United States in the guidelines for registration of biorational pesticides (Subdivision M of 40 CFR Part 158). A discussion of the regulatory issues requires some reference to the accompanying scientific developments. The potential application of chemicals that affect insect behavior and development appeared an extremely promising approach to the reduction of adverse environmental and health impacts associated with many conventional pesticides. In addition to these benefits, the new biopesticides generally affected a very specific range of target species. However, although juvenile hormones and semiochemicals offer exciting new approaches to pest control, and are potentially valuable components of pest management strategies, acceptance of these techniques has been slow. Commercial development has been difficult for several reasons. Regulatory requirements may appear burdensome. Unconventional pest-control technologies may call for special formulations or application equipment. It may not be easy to establish the efficacy of non-lethal potential techniques. Investigators who derive funds from the public sector may have neither responsibility nor resources to carry the technology beyond the experimental stage. Because most activities in this field have been heavily research-oriented, few workers have possessed the additional resources to obtain safety data or data to satisfy regulatory requirements. Difficulties in preparing and administering guidelines for registration of biopesticides lie in the novelty of the pest control agents and the diversity of the techniques involved in their effective use. Rapid advances in molecular biology and other disciplines continually strain the capabilities of regulators who are responsible for making safety assessments regarding pest-control agents. Although regulatory authorities are familiar with conventional pesticides, safety assessment of biopesticides calls for totally different approaches.     

Manufacture of optically active materials: An agrochemicals perspective

Against a background of the growing importance of single enantiomer agrochemicals, practical technologies for their production are reviewed. Methods range from extraction of natural products through to asymmetric synthesis and encompass physical, chemical and biological techniques.     

Recent advances in computational fluid dynamics relevant to the modelling of pesticide flow on leaf surfaces

Increasing societal and governmental concern about the worldwide use of chemical pesticides is now providing strong drivers towards maximising the efficiency of pesticide utilisation and the development of alternative control techniques. There is growing recognition that the ultimate goal of achieving efficient and sustainable pesticide usage will require greater understanding of the fluid mechanical mechanisms governing the delivery to, and spreading of, pesticide droplets on target surfaces such as leaves. This has led to increasing use of computational fluid dynamics (CFD) as an important component of efficient process design with regard to pesticide delivery to the leaf surface. This perspective highlights recent advances in CFD methods for droplet spreading and film flows, which have the potential to provide accurate, predictive models for pesticide flow on leaf surfaces, and which can take account of each of the key influences of surface topography and chemistry, initial spray deposition conditions, evaporation and multiple droplet spreading interactions. The mathematical framework of these CFD methods is described briefly, and a series of new flow simulation results relevant to pesticide flows over foliage is provided. The potential benefits of employing CFD for practical process design are also discussed briefly. © Crown copyright 2009. Reproduced with permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

我国化学肥料和农药减施增效综合技术研发顶层布局与实施进展

化学肥料和农药是保障国家粮食安全和主要农产品有效供给不可替代的投入品,2015年我国以占世界7%的耕地面积,投入了超过世界总量33%的化肥农药。因此,围绕解决我国化肥农药过量施用带来的生态环境污染、农产品质量安全、耕地质量下降、生物多样性破坏、农产品生产成本持续升高等问题已成为关注重点。2016年至今,"化学肥料和农药减施增效综合技术研发"试点专项以突破减施途径和创新减施产品与技术装备为抓手,聚焦粮食作物、经济作物、蔬菜、果树等重要农产品,依托农业产业政策进行了一体化实施。本文综述了此专项的整体布局、实施效果、科技产出、推广成效和管理经验,统计分析了研发、试验、转化、推广过程中的年度任务部署、中央财政资金分布、主持单位及课题单位分布、参与人员结构层次等相关数据,并总结了基础理论研究、共性关键技术、集成示范推广3个研究领域的阶段性成效,以期为减肥减药领域相关科研人员、推广机构、管理部门、技术用户、经营主体等提供参考。     

Recent Trends in Weed Control in Freshwater1)

While in many situations, such as irrigation and drainage ditches, the unobstructed movement of water is paramount and complete control of the weeds is needed, most freshwater nowadays has many functions some of which involve biological systems in which weeds play an important part. Trends in the development of new weed control techniques aimed at replacing traditional hand cutting methods while maintaining the required condition of the water are briefly reviewed. These include mechanical, chemical and biological methods all of which contain potentially valuable tools for the management of freshwater ecosystems.     

Studies of crop loss in potato blight caused by Phytophthora infestans

Relationships between healthy haulm area (HHA) and yield, and between losses of HHA and yield in the potato late blight system, were evaluated in several seasons and fields variously affected by the disease in Israel. The results showed that because of the different yield potential of potatoes cultivated in different conditions, evaluation of crop losses cannot be separated from evaluation of yield potentials of the crop as influenced by environmental and cultural factors.
In one calculation the yield and the HHA in the healthiest plot in each field were equated to 100% and losses in other plots were derived from comparisons with this plot. In such a calculation the relationships of yield loss to HHA loss in all fields and seasons fitted one regression equation, and a high correlation was obtained between both parameters. However, the actual haulm areas and yield weights differed widely from one field to another, even in the healthiest plots. Also, a similar percentage of destroyed haulms sometimes corresponded to different areas of the remaining haulms and to different yields. So no correlation was found between HHA and yields over all fields and seasons. Such a correlation was found only for several plots, variously affected by late blight, in the same field and season and in different fields and seasons yields responded in a different way to increases in HHA.     

Effect of haulm destruction supplemented by cutting off roots on the incidence of black scurf and skin damage,flexibility of harvest period and yield of seed potatoes in field experiments

In field experiments, supplementing chemical haulm destruction (CHD) with cutting off roots resulted in a lower incidence of black scurf and skin damage (ripping off the skin) at harvest date than CHD alone. The lower susceptibility to skin damage at harvest allowed harvesting to beging on an earlier date, when only a few sclerotia ofRhizoctonia solani had developed. Furthermore, black scurf often developed more slowly after haulm destruction if roots had been severed and this enabled harvesting to be postponed.At harvest, gross yield was highest if roots had not been cut through prior to CHD: the extra weight existed merely of water. Weight loss during storage, however, as well as grading losses resulting from black scurf were greater after CHD alone. This resulted in an equal or even lower net yield after CHD alone than after CHD supplemented by root severing. The favourable effects of supplementing CHD with cutting off roots almost equaled those of the mechanical removal, often called haulm pulling or plant pulling. Factors that may affect the development of black scurf are discussed.Samenvatting Pootaardappelen raakten minder bezet met lakschurft en werden minder ontveld bij de oogst na looftrekken of na wortelsnijden plus doodspuiten dan na loofklappen plus spuiten. Al vanaf de derde dag na trekken of wortelsnijden plus doodspuiten was de mate van ontvelling zo gering, dat met het oogsten kon worden begonnen. Op zo'n vroeg tijdstip na loofdoding konden knollen worden geoogst met nog weinig lakschurft, want de stimulering van lakschurft werd pas zichtbaar vanaf 7 à 10 dagen na loofdoding. Lakschurft ontwikkelde zich het traagst na looftrekken. Ook wortelsnijden bij het doodspuiten gaf meestal een tragere ontwikkeling van lakschurft dan klappen plus spuiten. Daardoor konden na wortelsnijden plus doodspuiten en vooral na looftrekken op nog latere tijdstippen knollen met weinig lakschurft worden geoogst.Na klappen plus spuiten was het bruto gewicht bij de oogst het hoogst. Dat meergewicht bleek louter uit water te bestaan en het verloop in knolvochtgehalte leek erop te wijzen dat de wortels nog gedurende een week na doodspuiten blijven functioneren. Dat gaf wel knollen met een hoger vochtgehalte die meer ontvelden en meer vocht en dus gewicht verloren. Dit groter gewichtsverlies bij bewaren en de hogere leesverliezen door lakschurft deden de meeropbrengst teniet: zo werd het netto knolgewicht na klappen plus spuiten, al naar gelang het moment van oogsten, meestal gelijk aan, of lager dan het netto knolgewicht na het trekken of na wortelsnijden plus doospuiten. In dit artikel worden de factoren besproken, die mogelijk van invloed zijn op de ontwikkeling van lakschurft.