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1.
《Field Crops Research》2005,91(2-3):263-271
The effects of shortage of agricultural labour, represented by direct-seeding technologies replacing transplanting, and of water scarcity, represented by limited water supply, on rice pests (pathogens, weeds, insects) were studied. The analysis was based on a field characterisation data set covering six sites in tropical Asia and several cropping seasons. Two-way ANOVAs and MANOVA were, respectively, used to test the effects of the two factors on individual rice pest injuries, and on the profile of injuries that an individual rice crop experiences over a cropping season. Fourteen injuries were considered, which individually were significantly (P < 0.05) influenced by crop establishment (nine injuries), by water management (11 injuries), or their interaction (nine injuries). Multiple analysis of variance indicated that rice injury profiles, regionally, are altered by both factors. The results suggested that injuries caused by some pests would be enhanced (e.g., brown spot, planthoppers) or reduced (e.g., stem rot, sheath blight, rice whorl maggot) by crop establishment shifting from transplanting to direct-seeding. Water shortages, proxied in our data by poor water management, would favour some injuries (e.g., sheath rot, brown spot, neck blast, whiteheads) or suppress others (e.g., stem rot, sheath blight). Very strong increases in weed infestation were observed with both direct-seeding and poor water management. The results are discussed with respect to pest management in rice.  相似文献   

2.
Growers' surveys took place in all sixteen potato growing regions of South Africa in 2013 and 2014. The agro-ecological climate of these regions is diverse and potato is produced in rainy or dry seasons, in winter or summer seasons, or year round. Growers were asked how often in ten years crops suffered more than 25% yield losses due to extreme weather events related to precipitation events such as hail, floods and droughts, and to temperature-related events such as frost and heat waves. Simultaneously they were asked their opinion about occurrence and severity of diseases caused by potato viruses, fungi and bacteria and pests such as nematodes, tuber moths, aphids and leaf miners. Weather related hazards resulted in losses over 25% virtually each year in the Gauteng growing region due to hail, frosts and floods; losses occurred less than once every five years, for example due to extremely high temperatures, in the Sandveld area where growers take a risk by producing potatoes in hot summers. Regarding the biotic factors, every pest or pathogen assessed was reported to occur on at least one farm in each growing region. Countrywide the lowest frequency of 50% was recorded for powdery scab whereas the insects tuber moths, leaf miners and aphids were reported most frequently, by between 88% and 98% of the growers. The complex of silver scurf and black dot resulted in the greatest yield losses in all growing regions, followed closely by tuber moth, early blight and the blackleg/soft rot disease complex. Yield losses due to potato virus Y, potato leaf roll virus and aphids were not reported as being very severe. When the growers' perceptions of severity of biotic factors were accumulated, significant differences between the regions appeared, with the Eastern Cape most prone with an accumulated score of 700 due to an array of pests and diseases, and the North–West with a score of only 50 mainly attributed to root knot nematodes. Growers were also asked how frequently biocides were applied to potato to control soil-borne organisms (nematicide and seed treatment), foliar fungi or insects. There were no significant correlations between frequency of biocide applications and severity of the disease as reflected in yield losses, most likely because growers use biocide applications as insurance against pests and diseases. This is common among crop farmers around the world. Although potato production in South Africa appears to carry more risks than production elsewhere, South African commercial potato growers are economically competitive when compared to growers in other areas of the globe, with comparable planting conditions and risks.  相似文献   

3.
This study aims to assess the risks and opportunities posed by climate change to potato growers in South Africa and to evaluate adaptation measures in the form of changes in planting time growers could adopt to optimise land and water use efficiencies in potato, using a climate model of past, present-day and future climate over southern Africa and the LINTUL crop growth model. This was done for distinct agro-ecosystems in South Africa: the southern Mediterranean area where potato still is grown year round with a doubling of the number of hot days between 1960 and 2050, the Eastern Free State with summer crops only and Limpopo with currently autumn, winter and spring crops where the number of hot days increases sevenfold and in future the crop will mainly be grown in winter. A benefit here will be a drastic reduction of frost days from 0.9 days per winter to 0. Potato crops in the agro-ecosystems will benefit considerably from increased CO2 levels such as increased tuber yield and reduced water use by the crop, if planting is shifted to appropriate times of the year. When the crop is grown in hot periods, however, these benefits are counteracted by an increased incidence of heat stress and increased evapotranspiration, leading in some instances to considerably lower yields and water use efficiencies. Therefore year-round total production at the Sandveld stabilizes at around 140 Mg?ha?1 (yield reduction in summer and yield increase in winter), increases by about 30% in the Free State and stays at about 95 t?ha?1 at Limpopo where yield increase due to CO2 is annulled by a shorter growing season. When the crop is grown in a cool period, there is an additional benefit of a reduced incidence of cold stress and a more rapid canopy development in the early stages of crop growth. In all three areas, potato growers are likely to respond to climate change by advancing planting. In Limpopo, a major benefit of climate change is a reduction in the risk of frost damage in winter. The relevance of these findings for potato grown in agro-ecosystems elsewhere in the world is discussed.  相似文献   

4.
Field tests for biological control of bacterial wilt of potatoes, caused byPseudomonas solanacearum, were conducted in Florida in 1984 and 1985. Potato seedpieces of tolerant (Ontario) and susceptible (Pungo and/or Atlantic) cultivars were immersed in a suspension of the avirulent, non-bacteriocinogenic strain ofP. solanacearum, B82, prior to planting in naturally-infested soil. Relatively low populations ofP solanacearum (2 to 4 log cfu/g soil) and root-knot nematodes (0 to 33 larvae ofMeloidogyne incognita/100 cm3 soil) were present in the soil before planting. In 1984, there was approximately a 50% reduction in incidence of bacterial wilt and brown rot in B82-treated plants of cultivar Atlantic, as compared with controls. With cultivar Ontario, on the other hand, disease incidence was very low and differences between treatments were not significant. In 1985, the incidence of bacterial wilt was low in all plots. Treatment with strain B82 reduced incidence of tuber brown rot in all cultivars, but differences between treatments were not significant at P = 0.05. There was a significant correlation, however, between incidence of wilt and root-knot nematode populations in the soil. Therefore, the possibility that control of bacterial wilt in 1984 was indirect,i e, via an effect of B82 treatment on root infection byM incognita, was examined. Greenhouse tests were conducted to determine the potential effect of seedpiece treatment with strain B82 on nematode infection of cultivars Atlantic and Ontario. In two out of three trials, the B82 treatment significantly reduced incidence of root knot. These results suggest that interactions of the biocontrol agent with root-knot nematodes may determine the effectiveness of a treatment designed for bacterial wilt control in the field.  相似文献   

5.
Vegetable production makes an intensive use of pesticides, and a major challenge is to build alternative cropping systems that can control pests and diseases with fewer uses of chemical products. An on-farm analysis was conducted in Southeast France to assess the efficacy of several cropping systems in simultaneously controlling two major pests: root-knot nematodes (Meloidogyne spp.) and lettuce drop due to Sclerotinia sclerotiorum. Ten cropping systems resulting from the combinations of three crop sequences and two alternative techniques, solarization and green manure, were assessed during two years. The use of solarization once a year or once every two years limited the occurrence of S. sclerotiorum. Sorghum green manure tended to increase S. sclerotiorum incidence; the effect was positively correlated with green manure duration. Especially when no vegetable was cropped in summer, the green manure crop duration was lengthened and this probably created soil conditions favorable to the development of the fungus. The incidence of root-knot nematodes was largely dependent on crop rotation: a melon crop in summer increased its incidence on the subsequent lettuce crops whereas a summer sorghum cover crop had no effect. The cropping systems that limited Sclerotinia development in soil tended to support the root-knot nematode populations. These results should motivate farmers and advisers to adopt a systemic analysis and take into account the various interactions among inoculum level, soil characteristics, crop rotations, and technical management options for designing sustainable vegetable production systems.  相似文献   

6.
Summary Growers are being faced with a conflic between the effects of specialization on increasing pest and disease problems (particularly late blight, Colorado beetle, cyst nematodes and tuber moth), and public opinion that will force them to reduce the use of pesticides. For this disease and these pests international research programmes are needed to develop parental lines and cultivars with durable resistance that can be used world-wide. This account is based on ‘The potato in world perspective’, a paper read at the First World Potato Congress held on 8–10 July 1993 in Charlottetown, Prince Edward Island, Canada.  相似文献   

7.
Plant parasitic nematodes associated with potato feed on roots and/or tubers. About 70 species, representing 24 genera, have been reported from potato. Since nematodes attack underground plant parts, there are no reliable foliar symptoms to show that nematodes may be the major cause of poor growth and reduced tuber yields. Potato roots damaged by nematodes may show lesions, abnormal proliferation of lateral roots, emerging white females and brown cysts. Nematode attacks may render plants vulnerable to other pathogens, so disease caused by microorganisms may have nematodes as an etiological component. Therefore, nematode damage may often have been attributed to other factors. In Scandinavia, potato cyst nematodes (Globodera rostochiensis and Globodera pallida) are by far the most important nematodes on potato. In Norway, the cost of compensations schemes due to imposed statutory regulations of potato cyst nematodes may some years exceed the compensation for any other pests or diseases organism in agriculture. Other important nematodes include root lesion nematodes (Pratylenchus spp.), stubby root nematodes (Trichodorus spp. and Paratrichodorus spp.), and potato rot and stem nematodes (Ditylenchus spp.). Root knot nematode Meloidogyne hapla is considered less important. Meloidogyne chitwoodi and Meloidogyne fallax are not known to be present in Nordic countries. In the control, crop rotations using non-host crops, alternating susceptible and resistant potato cultivars, are an important control measure. However, the use of resistant potato cultivars requires knowledge of the species and pathotypes present in the field.  相似文献   

8.
Nematode pests parasitise and cause substantial crop yield and quality losses to a wide range of crops worldwide. To minimize such damage, the exploitation and development of alternative nematode control strategies are becoming increasingly important, particularly as a result of global efforts to conserve the ozone layer as well as our soil and water substrates. Inclusion of Brassicaceae crops in cropping systems is one such alternative and has been demonstrated in most cases to be effective in managing the top-three rated economically important nematode pests, viz. root-knot (Meloidogyne), cyst (Heterodera and Globodera) and lesion (Pratylenchus) nematodes as well as others. In the past nematode pests were and still are generally managed successfully by the use of synthetically-derived nematicides, which are progressively being removed from world markets. However, fragmented and limited information about the use of Brassicaceae crops as a nematode management tool exists in various countries. The need thus arose to summarize, compare and discuss the vast amount of information that has been generated on this topic in a concise article. This paper therefore represents a comprehensive, practical and critical review of the use and effect(s) of Brassicaceae-based management strategies and the biofumigation and cover-crop/rotation characteristics of Brassicaceae in reducing nematode-pest population levels in global cropping systems.  相似文献   

9.
Wild potatoes are important sources of genes for resistance to disease and insect pests. A collection of wild Mexican and South AmericanSolarium species from the US potato Genebank was evaluated under laboratory and/or field conditions for their reaction to late blight (Phytophthora infestans), Colorado potato beetle (CPB,Leptinotarsa decemlineata Say), and blackleg (Erwinia carotovora subsp.atroseptica (van Hall) Dye) in order to identify individual genotypes with multiple resistance genes. Late blight inoculations using aggressive isolates (US-8/A2 and US-11/A1 mating types) of P.infestans revealed a wide range of variation for resistance between and within the accessions of the wild species tested. For late blight, susceptible as well as moderately to highly resistant genotypes were observed in all the species tested. However, at least one accession from the three Mexican and one South American wild diploid species tested showed a relatively uniform high level of resistance toP. infestans. These includedS. bulbocastanum, S. pinnatisectum, S. cardiophyllum, andS. circaeifolium. Two accessions from South American speciesS. commersonii were highly susceptible to late blight. For the Colorado potato beetle test, only one species,S. pinnatisectum appeared uniformly resistant to CPB under field conditions. Results of screening for blackleg resistance showed that there were major differences between genotypes in the wild species. Accessions ofS. circaeifolium PI 498119 andS. bulbocastanum PI 243504 were identified as having significantly higher blackleg resistance than cultivated potato and the other wild species tested. However, genotypes from these two accessions were more susceptible to late blight and CPB. Characterization of theP. infestans isolate P1801C.16 used for late blight evaluation and multi-locus isolate tests using US-8/A2 and US-11/A1 races revealed that the resistance inS. pinnatisectum genotypes tested corresponded to a race-non-specific genetic system, which was different from any existing R genes.Solanum pin-natisectum genotypes with both high levels of late blight and CPB resistance as well as blackleg resistance genotypes identified in the present study represent a diverse gene pool that may be useful for development of new potato cultivars with multiple disease and insect resistance. The potential utilization of these valuable sources for improvement of cultivated potato is discussed.  相似文献   

10.
Effects of pest and soil management systems on potato diseases   总被引：1，自引：0，他引：1  
Long-term cropping systems research is important in order to reduce production costs, to control crop pests, and to optimize the sustainability of agro-ecosystems. Soil amendment use, improved disease management practices, and careful cultivar choice are some of the potential components for improving potato production systems. This research was conducted in long-term cropping systems plots in order to evaluate the impact of soil amendments, pest management practices, and cultivar on foliar and soil-borne potato diseases and to assess the relationships of soil and pest management practices to disease levels and soil microbial activity. Fungicide applications for management of foliar diseases varied between the pest management systems (e.g., biological, reduced input, and conventional). Incidence of potato foliar diseases was quantified five times during the cropping season. The impact of soil amendment and pest management practices on soil microbial activity and tuber-borne diseases was also investigated. Low incidences of foliar and selected soil-borne diseases were recorded. Disease levels varied between years, cultivars, pest management, and soil amendments. Significant differences between cultivars were detected for early blight, white mold, and black dot. The cultivar Superior had higher incidence of white mold and black dot, while cv Atlantic had higher early blight incidence. Pest management system significantly affected foliar early blight incidence in 1998, but not in 1997. Pest management system did not affect late blight, white mold, or black dot incidence, or tuber disease incidence in either year. The addition of soil amendments significantly impacted tuber black dot incidences. Microbial activity responded to increasing temperature as the season progressed and was significantly enhanced by the addition of manure and compost soil amendments; however, lower disease incidence was not associated with increased microbial activity. While pest management practices were not major determinants of disease levels in these experiments, the results show that soil amendments can increase incidence of selected tuber diseases and microbial activity in soils.  相似文献   

11.
Diploid interspecific hybrids from crosses betweenSolanum tuberosum haploids andS. canasense, S. multidissectum, andS. tarijense, along with tetraploid and hexaploid somatic hybrids S.tuberosum (+)S. commersonii, were screened for resistance to blackleg and tuber soft rot byErwinia carotovora subsp.atroseptica andE. carotovora subsp.carotovora. Among the diploid hybrids, those involving clone mlt la of S.multidissectum and tar 2b ofS. tarijense yielded the highest number of genotypes resistant to both blackleg and tuber soft rot. By contrast, all the hybrids involving clone tar 1lb ofS. tarijense were susceptible to both bacterial diseases. As far as resistance of somatic hybrids is concerned, the most interesting genotype was the tetraploid one which showed resistance to both blackleg and tuber soft rot Significant correlations were found betweenE. carotovora subsp.atroseptica andE. carotovora subsp.carotovora both in resistance to blackleg and in resistance to tuber soft rot, suggesting that resistance to the two subspecies is controlled by the same gene/s or that the relevant genes are linked. On the other hand, correlations between blackleg and tuber soft rot were never significant, indicating that different mechanisms may control resistance in tuber and stems. Alternatively, the resistance could be controlled by the same gene/s under a different spatial/temporal expression pattern. Twelve diploid sexual hybrids and one tetraploid somatic hybrid were selected for resistance to blackleg and/or tuber soft rot and for tuber characteristics.  相似文献   

12.
Linolenic acid is a precursor to components in plant defense responses to pests and pathogens. Soybean cultivars with altered seed linolenic acid contents have been developed for improved oil qualities, specifically reduced fatty acid content with increased stability. We examined how three common soybean pests, the soybean cyst nematode (SCN, Heterodera glycines), brown stem rot (BSR) caused by Cadophora gregata and the soybean aphid (SBA; Aphis glycines), affect yield and seed linolenic acid percentage of low linolenic acid cultivars. In a micro-plot field experiment, soybean cultivars with varying concentrations of linolenic acid in the seed (ultra-low or low) and resistance to SCN (susceptible or resistant) were grown at a central Iowa research farm. Plots were kept free of pests (control) or artificially infested with a single pest (SCN, BSR or SBA) or the combination of all three pests (multiple pest). The use of resistant cultivars (SCN and BSR) or an insecticide at an economic threshold (SBA) was analyzed to determine the efficacy of current management recommendations for low linolenic acid soybean production. Seed was collected at the end of the season to measure yield and grain composition. All three pests alone or in combination were capable of reducing yield, but only the three pests in combination were capable of affecting seed linolenic acid percentages, increasing linolenic acid percentages by 11.7% in SCN-susceptible cultivars. For all three pests, current management recommendations (resistant cultivars or economic thresholds) provided protection of both yield and grain composition, indicating no changes in management are necessary for altered linolenic acid soybean cultivars.  相似文献   

13.
Potato storage tuber rots caused by the late blight and pink rot pathogens at harvest can cause severe economic losses, warranting the need for effective post-harvest fungicide applications. The purpose of this study was to evaluate the efficacy of select post-harvest fungicides in reducing tuber infections by the late blight and pink rot pathogens when applied at various post-inoculation time intervals. ‘Russet Burbank’ potatoes were inoculated by submersion in an aqueous suspension ofPhytophthora infestans orPhytophthora erythroseptica zoospores at 0, 1, 2, 4, and 6 h prior to receiving a post-harvest treatment. Products evaluated were zoxamide (various rates and formulation), phosphite (335 g a.i./MT), and a hydrogen peroxide/peroxyacetic acid mixture (HPPA, 9 g a.i./MT), all applied at 2.08 L/MT of tubers as a low pressure spray prior to storage. Zoxamide and phosphite significantly reduced late blight and pink rot incidence and severity when applied immediately after inoculation. HPPA was less effective at controlling disease development. Phosphite was effective at reducing late blight development at all time intervals up to 6 h post-inoculation (7% vs 80% in untreated). Zoxamide appeared to have good post-harvest disease control if applied soon after inoculation. The maximum time intervals between inoculation and treatment where significant reductions in pink rot incidence were observed was 0 h for HPPA (28%), 2 h for zoxamide (55%; 64 g a.i./MT) and 6 h for phosphite (13%) compared to the untreated (73%). Phosphite provided consistent disease control even when applied several h after inoculation and has potential to be a reliable post-harvest fungicide for the potato industry.  相似文献   

14.
Summary This contribution presents highlights of the oral and poster presentations in the various sessions of the 14th Triennial Conference of the European Association for Potato Research, held in Sorrento, Italy, May 1999. It is based on the reports of the session chairpersons and the book of abstracts. The paper reports the progress made in many aspects of potato research, but also stresses the need for further collaborative work, especially in the fields of molecular physiology, marker assisted breeding, control of late blight, potato tuber moth and other pests and diseases, stress physiology and stress resistance, and sustainable cropping systems with both short and long cycle potato crops.  相似文献   

15.
Some disinfestants are claimed to be more effective than others in controlling ring rot (Corynebacterium sepedonicum) and blackleg (Erwinia carotovora varatroseptica) bacteria on contaminated surfaces. Of the readily available disinfestants tested mercuric chloride (0.1%) and formaldehyde (2% and 5%) were the most effective against blackleg bacteria, and bleach (10%) mercuric chloride (0.1%) and formaldehyde (5%) were the most effective against ring rot bacteria on metal, wooden and burlap surfaces.  相似文献   

16.
Innovative methods less invasive for man and environment are needed to solve the problem of weeds, pests and diseases in cropping systems. Soil solarization is one practice that involves passively heating soil covered by a thin clear plastic film for several weeks during the periods of high solar radiation before the crop is planted. Soil solarization treatments were repeated to verify their long-term effectiveness on soil microbial biomass and its respiration activities, in addition to yield response and root-knot nematodes control in tomato and melon crops following soil heating. Experiments in greenhouse were carried out in Southern Italy (40°24′ N, 16°28′ E) during the summer of 1998, 1999 and 2000 on soil infested by the root-knot nematode Meloidogyne javanica. Crop yields and fruit quality of all vegetable crops were positively affected by repeating solarization for two and three years, compared to an untreated soil and soil treated once in 1998. Solarization was effective in controlling root-knot nematode damage, but solarization affected the soil biota populations and their activities as a consequence of repeated treatments.  相似文献   

17.
西南山区由于其立体气候的多样性而使马铃薯发生多种病虫害,造成产量的不稳定性。通过一系列的问卷调查和大田观察取样以及实验室病理检测,结果说明晚疫病、病毒病和青枯病是本地区最重要的病害。晚疫病常年造成１０％～３０％的产量损失,且每隔数年有一次大流行而造成更大的产量损失。种薯因病毒和其它病菌感染而不同程度地影响到产量的发挥。青枯病的发病规律较为复杂且较难预测控制。这几种病害的发生程度与作物生长季节、海拔、种薯年龄、品种、农艺措施等等密切相关。现有品种间发现有抗晚疫病和青枯病的差异。土样根系样中发现有各种寄生性线虫存在,但其危害性特别是与青枯病的关系有待进一步研究明确。２８星瓢虫是本地区危害最重的害虫。本文还列举讨论了各种病虫害防治措施。  相似文献   

18.
Infection of potato plants and tubers with the bacteriumErwinia carotovora subsp.atroseptica produces blackleg and soft rot diseases, which cause significant losses to crops and stored potatoes. In order to obtain resistance against this bacterium, the genechly encoding the enzyme lysozyme from chicken was introduced into potato plants (cv. Desirée) viaAgrobacterium- mediated transformation. Sixty-three and 69 transgenic potato clones were evaluated in the greenhouse for resistance to blackleg and soft rot diseases, respectively. Results reported in this paper indicate that 21%-29% of the potato clones showed increased resistance to infection by the bacteriumE. c. subsp.atroseptica T7, as revealed by a reduced severity of blackleg or soft rot symptoms. Nine clones showing different levels of resistance were selected for further molecular analysis. The number of copies of the transgene integrated in the plant genome of these clones was estimated by Southern blot analysis. The level of transgene expression, detected by Northern blot analysis, correlated with the level of resistance detected in these clones.  相似文献   

19.
Studies to estimate root-knot nematode infestations on cucumber were conducted during mid- to late-season at 378 randomly selected sites in 126 villages of the four districts across the Pothowar zone of the country. The overall mean infestation of root-knot nematodes in the region was found to be 15.66%. The studies revealed variations in the incidence and severity of root-knot nematodes in the four districts. The incidence of root-knot nematodes was the highest in Rawalpindi district (21.86%), followed by 13.89% in Attock. Of the four districts, the minimum incidence of 10.97% was recorded in Jhelum district. The maximum mean severity (3.79), measured in terms of the galling index, was found in Rawalpindi district, while the minimum (1.86) was observed in Jhelum district. The mean severities of root-knot nematodes in the districts of Attock and Chakwal were 2.66 and 2.19 respectively. Variations in incidence and severity were also observed among subdivisions of the districts. Of all the associated species of root-knot nematodes, Meloidogyne incognita constituted 78.53%, Meloidogyne javanica 19.03%, Meloidogyne arenaria 1.82% and Meloidogyne hapla 0.62%. M. incognita and M. javanica were recorded in all of the districts, with M. incognita predominating. M. incognita as a pure population was recorded in 29.63% of the villages, while the other three species were found as mixtures. The most common mixed population was M. incognita and M. javanica, observed in 70.37% of villages in the region. M. arenaria and M. hapla were not found together in any of the population mixtures. The results indicate that cucumber is severely attacked by root-knot nematodes, warranting adoption of strict control measures for its management.  相似文献   

20.
Potato cyst-nematodes,Globodera pallida andG. rostochiensis (golden nematode), and their preferred host, the potato, originated in the Andes of South America. Both were introduced into Europe from the Andean region, the potato about 1570 and the nematode nearly 300 years later. Potato cyst-nematodes are believed to have been introduced into Europe in the 1850’s along with potato collections from the Andes for use in breeding for late blight resistance, but the nematodes went unnoticed until 1881. Since that time the nematodes have spread to virtually everywhere that potatoes are grown, as one or both species have now been reported from 47 countries. It is believed that the golden nematode was introduced into the U.S.A. from Europe on military equipment brought back after the First World War to Long Island, NY, but the nematode was not recognized until some 20 years later. Yield losses in countries with general infestations of potato cyst-nematodes are probably 9% or more; the potential for losses is greatest in countries where average yields are greatest, such as the U.S.A. Good resistance to the pathotype of the nematode that occurs in the U.S.A. is commercially available. If all potatoes grown in the U.S.A. contained this resistance, further spread would be restricted and the golden nematode could perhaps be eliminated from the U.S.A.; but the present supply and diversity of resistant varieties are insufficient for the total potato acreage. Restricting spread of the golden nematode in the U.S.A. minimizes costs borne by growers and government agencies in dealing with the pest. At present, the most promising approach to restricting spread is through management systems developed for keeping nematode densities below the critical level above which spread will occur. If the golden nematode is to be contained, management systems must eventually be applied to all potato acreages. Increased research effort is needed to develop resistant varieties, resistance to a broad range of pathotypes, nematode management systems, and biological control  相似文献   

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