牛猝死症的研究进展

牛猝死症(sudden death syndrome, SDS)又称为暴死症或急性死亡综合征,近年来许多病畜前期不见任何症状就突然死亡。该病一般病程也不超过12 h,各年龄段的牛均能发病,是一种发病急、死亡率高的疾病。发病牛以全身实质性器官衰竭以及消化道出血、小肠坏死为主要病变特征。目前发现该病的致病因素较多并且给中国的养牛业造成了巨大经济损失。本综述就近年来牛猝死症的发病原因、临床症状、病理变化以及防治措施等研究进展作总结概述,以期对该病的深入研究提供科学的参考。     

白内障发病机制与防治策略的研究进展

白内障是全球首位致盲性眼病.随着人口老龄化加剧,白内障将导致巨大的社会和经济负担.目前,手术治疗作为唯一的治愈手段,仍存在个体疗效差异、手术禁忌症、并发症及经济负担等诸多局限性,已不能满足当前社会需求.因此,研究白内障发病机制,找寻白内障潜在的治疗药物一直是研究的热点.本文基于团队目前的工作内容,从白内障发病机制、白内障模型进展及白内障防治药物的开发筛选等方面对白内障的发病机制及防治策略进行综述.     

玉米病虫害防治技术分析

玉米作为我国的主要粮食作物,随着种植面积的逐年扩大,玉米病虫害发生也逐年加重,严重威胁着玉米生产安全。本文主要介绍了玉米主要病虫害的种类、发病症状、发病原因及其具体的防治方法,以期为玉米病虫害防治提供参考。     

疟原虫与疟疾

结合国内外研究进展,简介了疟原虫的生物学特性,疟疾的发病机理,目前我国疟疾流行概况和防治策略。     

葫芦岛市保护地番茄灰霉病的发生和防治

葫芦岛市保护地番茄灰霉病的发生和防治齐素芳,王宏,马宗超（葫芦岛市植保站,１２５０００）番茄灰霉病在保护地的番茄栽培中,已成为一个主要的病害。据我们调查,保护地番茄一般发病果率为２０％,重病果率高达８０％以上。该病流行年份发病面积约达５０－７０％,成...     

烟草角斑病的发生及防治研究

烟草角斑病是一种常见于烟田中的细菌性病害,一旦发生,严重影响烟草产量.本研究介绍了烟草角斑病的病原菌的生物学特征和侵染规律,探究控制病害的有效方法.通过研究该病在田间发病因素以及发病规律的影响因素,更好地了解其传播方式和危害程度,从而制订相应高效的防治措施.最终提出预测发病趋势并提前做好防病准备是预防该病的最佳策略之一,可以结合气候变化、流行规律以及病害历史数据等,开展综合分析与研究,从而有效地控制该病的发生.     

苹果虎皮病的综合防治

苹果虎皮病是某些品种苹果在低温贮藏的中后期发生的一种最严重的生理性病害。该病的主要症状是在果面上（通常是绿色部分）出现不规则且凹陷的褐色至深褐色病斑。发病初期病斑面积较少,皮下果肉组织正常;发病后期病斑可延至整个果面,部分果肉也变褐。病果极易染菌而腐烂,常造成重大经济损失。目前我国栽培的许多苹果品种易发生虎皮病,如新红星、红星、国光、青香蕉苹果等。近年来我国苹果产贮量逐年增加,为提高贮后苹果质量、延长苹果贮期,有必要加强虎皮病的防治工作。目前可以采用以下技术来防治虎皮病的发生。1．首先采取合理的…     

云南省烟草丛顶病发生规律及其综合防治

烟草丛顶病在云南西部烟区暴发流行,给烟叶生产带来严重损失,是烟草最主要的病害之一.目前烟草丛顶病得到了有效控制,但仍是烟区潜在的危险性病害.本文对烟草丛顶病的危害特征、发病症状、病原物、流行发病规律和综合防治研究进展进行了综述,提出了烟草丛顶病综合防治集成技术,可为进一步研究和防治烟草丛顶病或类似病害提供参考.     

全树刮表皮涂抹梧宁霉素发酵液防治苹果树腐烂病试验

苹果树腐烂病是由苹果黑腐皮壳菌引起的一种病害,其表现是病原菌在生长发育肘,消耗果树的营养,使果树韧皮部腐烂,影响水份、养份的输送,直接危害果树生长,严重时使果树枝干韧皮部形成环腐,可致整枝、整株死亡。为防止腐烂病的发生和蔓延,主要采用药物涂抹患病处,杀死病原菌,进行局部治疗。利用这种传统的方法治疗腐烂病,对发病轻的果树效果好,发病重的果树效果差,且重犯林率高,在果树生长期需要经常监视,重复劳动多,整园防治效果差。即使每年都认真防治,盛果期的果园发病也非常严重。例如,朝阳县北四家乡果园,树龄为34年…     

月季白粉病的防治

白粉病是月季栽培中最常见、危害最为严重的一种病害。它主要危害植株的叶片,同时也可危及嫩梢、枝条、花蕾与花梗等处。在发病初期,病部出现褪绿黄斑,继而逐渐扩大,叶背病斑处着生一层白色粉状物,如果继续扩展,可使整个叶片背面与嫩梢处都呈现灰白色。严重时叶片扭曲反卷,嫩     

Absolute and relational control of a sequential auditory discrimination by pigeons (Columba livia)

Recent evidence indicates that pigeons can readily learn visual discriminations based on both absolute and relational stimulus factors. To examine how these two types of control function in their non-dominant auditory modality, we tested four pigeons in a go/no-go sequential auditory discrimination in which both absolute and relational cues were redundantly available. In this task, sequences of different sounds created from one set of pitches were reinforced, while different sequences created from another set of pitches and any same sequences made from either set of pitches were not. Across three experiments, we independently varied the relative discriminability of the absolute and relational components. The pigeons were consistently and primarily controlled by the absolute fundamental pitch of our notes in all of the experiments, although this was influenced by the range and arrangement of the pitches used in each set. A majority of the pigeons also demonstrated relational control when this component was made more salient. The more robust control exhibited by absolute factors is consistent with the comparative hypothesis that birds in general may have a well-developed aptitude for processing absolute pitch in many auditory settings. The relational control is consistent with our recent evidence of same/different auditory learning by pigeons.     

Fermentation media and production of exotoxin by three varieties of Bacillus thuringiensis

The insecticidal activities of the exotoxin produced by three varieties of Bacillus thuringiensis grown in six fermentation media were determined by testing the supernatants against larvae of the house fly, Musca domestica, and the black cutworm, Agrotis ipsilon. The activities of the exotoxins from the isolates varied when they were grown in the same medium and also when they were grown in different media. When an isolate of B. thuringiensis var. thuringiensis, and of var. tolworthi were grown in proflo broth, the supernatants produced were more toxic to house fly than to black cutworm larvae, indicating the presence of more than one exotoxin. Autoclaving the supernatants for 15 and 30 min further demonstrated the presence of several exotoxins.     

The concept of mobility in single- and double handed manipulation

The concept of mobility describes an important property of the human body when performing manipulation tasks. It describes, in a sense, how easy it is to accelerate a link or a point on the manipulator. Most often it is calculated for the end-link or end-point of the manipulator, since these are important for the control objective of the manipulator. Mobility is the inverse of the inertia experienced by a force acting on the end-point, or a combined force and torque acting on the end-link. The concept has been used in studies of reaching tasks with one arm, but thus far not for bi-manual manipulation. We present here the concept for both single-handed and double-handed manipulation, in a general manner which includes any type of grip of the hands on the object. The use of the concept is illustrated with data on the left and right arm in a golf swing.     

Susceptibility of nymphs and adults of Diaphorina citri to the entomophathogenic fungus Hirsutella citriformis

The susceptibility of nymphs and adults of Diaphorina citri to infection by Hirsutella citriformis was evaluated. We also studied the ability of adult D. citri that had been contaminated with fungal conidia to transmit infection to nymphs. Diaphorina citri nymphs were more susceptible than adults. Adults were not able to transmit conidia to nymphs and cause infection.     

Effects of temperature and instar on the efficacy of Bacillus thuringiensis var. israelensis and Bacillus sphaericus strain 1593 against Aedes stimulans larvae

Laboratory trials of Bacillus thuringiensis var. israelensis (serotype 14) and B. sphaericus strain 1593 against field-collected Aedes stimulans showed that susceptibility declined with increasing instar and decreasing temperature. Test results with B. sphaericus were more erratic than with B. thuringiensis, and the efficacy of the former declined more rapidly with decreasing temperature. B. thuringiensis was significantly more active than B. sphaericus under all treatment conditions. These results indicate that the effective use of this strain of B. sphaericus as a mosquito biological control agent may be limited to warm water situations against more susceptible species.     

Interaction of Four Soybean Cultivars with Subsoiling and a Nematicide

Yields of four soybean, Glycine max, cultivars were increased with subsoiling under the row and application of the nematicide, DBCP i 1,2-dibromo-3-chloropropane) in Tiflon sandy loam heavily infested with the root-knot nematode Meloidogyne incognita. These cultivars represent four maturity groups: very early (V), "Essex'', early (VI), "Davis'': medium (VII), ''Ransom''; and late (VIII), '' Hutton ''. The average increase for the four cullivars was about the same for subsoiling or DBCP. When the treatmcnts were used together, the increase was greater than when either was used alone, but the effects were not additive. Increased yields were obtained with subsoiling and DBCP for the most nematode resistant cultivar, Hutton, as well as for the most susccptiblc, Davis. Subsoiling reduced root-knot galling in nonfumigated plots but did not affect it in fumigated plots. On 12 September, M. incognita larvae were most numerous at the 0- to 20 cm depth, intermediate at 20 to 33 cm depth and least numerous at 33 to 46 cm depth, Subsoiling did not affect larval populations at the three levels.     

Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies

• 1 Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year.
• 2 We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling.
• 3 The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat.
• 4 Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.

     

Characterization of esterases in malathion-resistant and susceptible strains of the pteromalid parasitoid Anisopteromalus calandrae

General esterase, malathion-specific carboxylesterase, phosphotriesterase, glutathione S-transferase, cytochrome P-450-dependent monooxygenase activity, and target site sensitivity were compared in malathion-resistant (R) and malathion-susceptible (S) strains of the parasitoid Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae). Activity against -naphthyl acetate was not significantly different in male and female wasps for either strain. General esterase activity ranged from 1.2-fold to 2.5-fold higher in the R strain compared with the S strain, but these differences between strains were not consistent. Based on V_max/K_m ratios estimated for a number of analogs of four substrates (-naphthyl acetate, β-naphthyl acetate, 4-methylumbelliferyl acetate, and p-nitrophenyl acetate) there was no evidence that general esterase activity was elevated or reduced in the R strain. Malathion-specific carboxylesterase (MCE) activity, determined by using 2,3-¹⁴C-malathion as substrate, was 10- to 30-fold higher in the R strain compared with that in the S strain. The MCE has a pH optima at about pH 7, is cytosolic, and is labile upon storage at −80°C. MCE activity could be recovered from native 10% PAGE gels and IEF–PAGE gels (pI=5.2), but the peak of MCE activity also contained the major peak of activity against -naphthyl acetate. There was no evidence for major involvement of phosphotriesterase, glutathione S-transferase, monooxygenase, or altered acetylcholinesterase in the resistance. These data suggest that an increased activity of a MCE in the R strain is the probable major mechanism conferring resistance to malathion in A. calandrae. This study provides the first characterization of a biochemical resistance mechanism in a parasitoid with a high level of resistance to an organophosphate insecticide.     

葱斑潜蝇防治指标及防治适期研究

研究表明葱斑潜蝇百株潜道 (X)与大葱产量损失率 (Y)之间呈显著的相关性 ,其相关回归式 :Y=-2 .8397+ 0 .0 30 4 8X。在大葱产量 30 0 0～ 6 0 0 0kg 6 6 7m2 时 ,经济允许损失率为 1 .4 7%～ 2 .94 % ,允许百株潜道为 1 4 1 .4～ 1 89.6条 ;防治指标拟定为百株潜道 1 5 0条。防治适期为成虫羽化高峰期至幼虫初孵期 ;大葱生育中、后期 ( 6～ 1 0月 )防治对于降低葱属作物的损失具有较大意义。药剂防治以含有阿维菌素的制剂和乐斯本效果较好。