调整玉米播期对玉米粗缩病控制作用研究初报

通过罩笼接虫和自然开放式状态下试验 ,对不同播期的玉米粗缩病病情进行了比较 ,明确了玉米敏感叶龄为可见叶 9叶以下 ,展开叶为 6叶以下。研究证实 ,将田间灰飞虱转移迁入高峰期与玉米敏感叶龄期错开 ,可以减轻玉米粗缩病的发病 ,春玉米播期 4月 10～ 15日 ,夏玉米在 6月 10～ 15日 ,能显著控制玉米粗缩病的危害。     

进境斑节对虾检疫和防治

本文系统地报道了进境斑节对虾亲虾及育苗期疫病的检疫方法、结果和防治措施。检出了多种致病性弧菌、微孢子虫和斑节对虾杆状病毒。细菌分离药敏试验和敏感药物防治是当前对付虾细菌病的先进方法。针对当前虾病,提出了加强检疫、建立育苗场用药指南、创造良好的育苗环境、防止虾病发生、培育壮苗的对策。     

云南河口香蕉黄化束顶病研究:Ⅰ.症状与发病规律

 作者通过连续六年的田间定点调查与研究认为发生在云南河口及其邻近县市香蕉上的黄化束顶病不同于已往记载的BBTV所致的香蕉束顶病。病株新抽叶短小、窄、叶缘失绿黄化或整叶白化;假茎外表面紫红色;果穗从假茎中不能或部分抽出;根部着生根结。病株地上部发病高峰表现在植株进入快速生长而原根系已腐烂、新根尚未形成的春季,而夏末秋初为根结形成高峰。健株根围接种根结线虫后表现典型的黄化束顶症状。田间增施氮肥加重发病,香蕉宿根年限越长病情愈重。连作地、熟地、旱作地分别较轮作地、荒地以及低洼稻作地的发病率高。部分病株进入雨季或移植长期隔置的香蕉土壤中能恢复正常生长。病害的自然传播与土壤密切相关。     

Spatial and stochastic simulation to evaluate the impact of events and control measures on the 1997-1998 classical swine fever epidemic in The Netherlands. II. Comparison of control strategies

Using the spatial, temporal and stochastic simulation model InterCSF, several alternative pre-emptive slaughter strategies that could have been applied in the Dutch Classical Swine Fever (CSF) epidemic of 1997–1998 were evaluated. Furthermore, effects of changes in some disease-spread and disease-control parameters were studied. InterCSF simulates the spread of CSF between farms through local spread and contacts (animals, transport and persons). Disease spread is affected by control measures implemented through different mechanisms (e.g. depopulation of infected farms, pre-emptive slaughter, movement control). The starting point for the evaluation of strategies was a simulated basic scenario, which mimicked the real epidemic. Strategies were compared using epidemiological as well as economic results. Economic results were generated by a separate model (EpiLoss) that calculated the direct losses and consequential losses for farmers and related industries. The comparison of the different alternatives to the basic scenario led to some general conclusions on the Dutch CSF-epidemic. Pre-emptive slaughter seemed to be an effective strategy to reduce the size of an epidemic, if started at an early stage. Economically, pre-emptive slaughter was not as expensive as expected; the resulting smaller size of the epidemic, combined with less welfare slaughter, led to much lower overall losses. Furthermore, although large movement control areas seemed effective in reducing the size of the epidemic, the total losses were relatively high because of subsequent welfare slaughter. If infection probabilities could be reduced, for example by improved biosecurity, the resulting epidemics would be much smaller.     

Classical swine fever in The Netherlands 1997-1998: a description of organisation and measures to eradicate the disease

The central and regional organisation of the campaign to eradicate the CSF epidemic in the Netherlands in 1997/1998 is described. The main instruments used in the campaign were based on stamping-out and movement restrictions specified by the European Union. Additional instruments were used for the first time, namely, pre-emptive culling of contact and neighbouring farms, compartmentalisation of transport, monthly serological screening in established surveillance areas and supervised repopulation of all farms in the former surveillance zone. Two other measures, the killing of very young piglets and a breeding ban were introduced to reduce production in established surveillance zones. Several factors complicated the eradication campaign, for instance, the late detection of the first infection; artificial insemination as a source of infection; the organisation of pig farming in the Netherlands, with its highly concentrated production and dependence on the transport of stock from one unit to another; insufficient rendering capacity; decreasing sensitivity of clinical inspection; and extremely high costs.     

Association between bovine-leukosis virus seroprevalence and herd-level productivity on US dairy farms

Bovine-leukosis virus (BLV; also termed ‘bovine-leukemia virus’) is a retrovirus that primarily affects lymphoid tissue of dairy and beef cattle. Our objective was to investigate the association between BLV infection and annual value of production (AVP) on dairy herds within the United States, as part of the USDA National Animal Health Monitoring System’s 1996 dairy study. 1006 herds (in 20 states) with at least 30 dairy cows were interviewed during 1996. The agar-gel immunodiffusion test was used to detect serum antibodies to BLV. 10–40 cows from each herd were tested and each tested cow was classified as negative or positive based on results of a single test.

A multivariable regression model was used with the 976 herds with complete data for analysis. When compared to herds with no test-positive cows, herds with test-positive cows produced 218 kg per cow (i.e. 3%) less milk. The average reduction in AVP was $ 59 per cow for test-positive herds relative to test-negative herds. For the dairy industry as a whole, BLV seropositivity was associated with loss to producers of $ 285 million and $ 240 million for consumers. Most of this $ 525 million industry loss was due to reduced milk production in test-positive herds.     

水杨酸与蔬菜作物抗性关系的研究进展

水杨酸在植物的抗病性方面发挥着重要的作用,近年来的研究表明,水杨酸在植物抗冷、热、盐、干旱、臭氧、重金属等环境胁迫方面有明显的作用。对近年来有关水杨酸在蔬菜抗逆境胁迫方面的研究进展进行综述,并提出一些研究思路。     

采后热空气处理对金冠苹果后熟衰老及病害的影响

金冠苹果采用38℃,72h或96h热空气处理,可降低0℃贮藏中果实的呼吸强度和乙烯释放量,延缓非溶性果胶的降解,维持较高的硬度、脆度,同时也会加速果皮的褪绿变黄和固酸比的上升,尤其是38℃96h处理的作用效果更为明显,显著提高了货架期后(20℃7d)苹果的质地品质和可接受程度,延缓衰老。苹果分别接种扩展青霉、灰葡萄孢霉,0℃和20℃条件下其病害发生率和腐烂均很严重,采用38℃96h热空气处理可以完全控制病害的发生,避免腐烂。可见,热空气处理一方面能延缓金冠苹果的后熟衰老,另一方面还能控制贮期病害的发生。     

Landscape features influence genetic structure of black-tailed prairie dogs (Cynomys ludovicianus)

Black-tailed prairie dogs (Cynomys ludovicianus) currently live in metapopulations in the parts of their range where plague, caused by the bacterium Yesinia pestis, has invaded. Prairie dogs are highly susceptible to the pathogen, with most animals within towns dying during Y. pestis outbreaks. A review of population genetic studies of prairie dogs demonstrates considerable differentiation between prairie dog towns. Despite declines and fluctuations in size of prairie dog populations, they continue to harbor considerable genetic variation. This results from continual dispersal and gene flow, likely along low-lying drainages that connect towns. When combined with estimates of population size, the landscape genetic approach described here will provide precise estimates of dispersal and gene flow, in addition to evaluation of long-term stability of prairie dog metapopulations.     

圈养小熊猫的疾病

小熊猫作为一种高度特化的素食性食肉目动物,在分类、系统进化及生态学等领域具有十分重要的研究价值,也是动物园里具有很高观赏价值的一种动物。为了更好地保护小熊猫免受疾病侵扰,做到有针对性的疾病预防,对近年来有关小熊猫疾病的报道进行了总结,并按病毒病、细菌病、真菌病、寄生虫病、代谢病、中毒病等进行了分类介绍。