柑桔的类病毒

柑桔裂皮病和木质陷孔病都是由类病毒或类病毒复合物引起的,根据类病毒的物理学特性和寄主上及映出的生物学特性、症状表现可分为了组.采用 sPAGE 检测技术可快速、准确、高效检测出类病毒的存在.同时还利用类病毒的致矮机理来控制柑桔的生长发育.     

杂草自动检测与选择性施药的可能性

多数杂草在田间呈局部分布,其滋生范围可在数年内基本保持不变,这就为田间杂草的选择性防治提供了可能,而选择性防治的关键技术是田间杂草的自动、有效检测。英国科学家对这一技术进行了探索,调查了多种杂草在禾谷类作物田间的分布;利用植物的形态特征和植物叶片的反光指数特征来区别、辨识杂草及定位其发生范围;采用装载有杂草辨识系统的喷雾机实施田间杂草的选择性防治;并结合田间绘图法提供的信息使杂草辨识系统更加有效和可靠.虽然这一技术尚有待完善,但杂草自动检测与选择性防治在实践上是完全可行的.     

东南亚水稻害虫的综合治理现状与展望

在南亚和东南亚,水稻害虫的综合治理仍处在其形成阶段,水稻抗虫品种和化学农药已成了主要的防治手段,而几乎忽视了当地天敌的价值。将来的工作应集中在:(1)鉴定害虫与天敌种类;(2)评价害虫的为害,并测定防治阈值;(3)制订取样或监测方法;(4)选取适当的防治对策;(5)综合治理.农民的培训是成功执行综合治理的关键,但向政策制定者讲授其原则也是十分紧要的.     

棉铃象甲棍式诱杀器

美国农业部农业研究所与私人企业联合开发出一种棍式诱杀器,能引诱和杀死棉铃象甲.此发明是通过多年对棉铃象甲习性和外激素的研究而得到的结果.该诱杀器由高4英尺、直径3/4英寸的木棍和套在木棍中部的诱杀帽组成.诱杀帽由塑料、引诱棉铃象甲的绿色颜料、棉铃象甲性诱剂、引诱害虫取食的刺激剂和对害虫毒性很大但对哺乳     

用RAPD分析和DNA指纹鉴别玉米小斑病菌O、C、T三个小种

目前通过病理学鉴定已发现玉米小斑病菌存在分别对玉米雄性不育T型、C型细胞质专化侵染的T小种和C小种(无细胞质专化致病性的相应称为O小种)。为了建立快速鉴别、监测O、C、T三个小种的技术,我们使用了近来建立的基于以带有任意序列单一寡核苷酸引物的DNA随机片段扩增技术进行了三个     

密植苹果园恶疫霉颈、根腐病的生物和化学防治

在不列颠哥仓比亚库特耐河谷中克里斯顿的密植苹果园对21个枯草芽孢杆菌菌系、1个产气肠杆菌菌系、土施和树干浸渍瑞毒霉、撒施磷酸二氯铵(NH_4H_2PO_4)防治苹果恶疫霉颈、根腐病的效果进行了8年试验评价,与对照相比,瑞毒霉能完全防治该病,NH_4H_2PO_4,产气肠杆菌B_8菌系及枯草芽孢杆菌AB_7、AB_8、BACT X、BACT_2和NZB_1菌系各处理均能显著减少感病株数;且枯草芽孢杆菌各菌系处理能增加树干直径。在大田条件下,这些桔抗菌所表现的防病效应也很理想。     

释放钝绥螨防治蔬菜烟蓟马

本文评价了两种钝绥螨:巴氏钝绥螨Amblyseius barkeri(Hughes)和瓜钝绥螨A.cucumeris(Oudemams)作为甘蓝害虫烟蓟马Thrips labaci生防因子的潜在能力,在初步试验中巴氏钝绥螨群集于菜球上。1987年在田间释放巴氏纯绥螨,每株释放不同数量,结果甘蓝球上的蓟马数量减少了,减少的程度与该螨释放的数量成比例关系,但对蓟马的为害却没有影响。1988年,在甘蓝植株上分期释放瓜钝绥螨,每次释放数量相同,结果是早期释放可压低蓟马的数量,减轻收获时的为害。结论是移植性释放钝绥螨是蔬菜蓟马的潜在有效的防治方法,不过要付之实用,释放时间和方法还有待进一步研究。     

硫代硫酸铵对土壤中除草剂寿命的影响

用于土壤的除草剂常与液体肥混用,可降低成本和提高时效。硫代硫酸铵(ATS)是一种通用的含硫液体肥,能降低土壤中微生物的作用速度。本文报道ATS对土用微生物降解除草剂效应期的影响。试验在温室和生长箱进行,采用粗壤土和粗粉砂土。当每克土施用0.3～0.8ml的ATS时,能延长除草剂2,4—D、甲绿胺、丙草丹、cinmethylin、燕草畏的有效控制期,但ATS对异丁草丹或异丙甲草胺的除草有效期影响非常小。延长2,4—D和丙草丹效应期的最低ATS用量为0.15ml/kg土(假设被耕土的容重为1.0,平均土层深度5cm,虽然就目前来说ATS这个用量费用太大,但是由于ATS应用广泛并且某些土用除草剂需要延长其在土壤中的寿命,所以对ATS花费太大的旧观念应该重新进行估价。     

Effect of puerperal mastitis in primiparous cows on milk production, cell count and culling

A retrospective cohort study was performed to investigate the effect of clinical mastitis in heifers during the first week post partum (p.p.) on subsequent health and productivity. Primiparous cows that had calved between August 15th, 1996 and August 14th, 1997 (n = 1389) were included in the study. Milk samples were collected from each quarter post partum prior to first milking. The predominant group of bacteria found were Staphylococcus spp. (69%) followed by Streptococcus spp.(12%) and E. coli (5%). Intramammary infections at calving increased the risk of clinical mastitis within the first week p.p. The cow incidence of mastitis until day 7 p. p. was 38%. Cows were classified into three groups. Group 1: Animals with clinical mastitis prior to calving (n = 35); Group 2: Animals with clinical mastitis between calving and 7 days p. p. (n = 503); Group 3: Animals without mastitis until 7 days p. p. (n = 851). Mastitis prior to parturition and mastitis within the first week p.p. increased the risk of further cases of mastitis and culling during the first 45 days of lactation. Milk yield of Group 2 was lower and somatic cell counts were higher than in Group 3.     

Molecular heterogeneity in clinical isolates of Malassezia pachydermatis from dogs

Molecular investigation of 16 strains, conventionally identified to be Malassezia pachydermatis, isolated from dogs in Japan was carried out by random amplification of polymorphic DNA (RAPD) and chitin synthase 2 (CHS2) gene sequence analyses. The RAPD band patterns of 13 clinical isolates were identical to that of standard strain of M. pachydermatis (CBS-1879). The other three clinical isolates were different from the standard strain of M. pachydermatis in RAPD patterns, and two of the three isolates were identical. About 620 bp genomic DNA fragments of the CHS2 gene were amplified from the same 16 clinical isolates of M. pachydermatis by polymerase chain reaction (PCR) and sequenced. The phylogenetic analysis of the nucleotide sequences of CHS2 gene fragments of the 16 clinical isolates revealed that the 13 strains were genetically very close to the standard strain of M. pachydermatis and the other two isolates were genetically close to the standard strain of M. furfur rather than M. pachydermatis. The remaining one isolate was phylogenetically distinct from all the seven Malassezia species reported so far.