我国高效苏芸金杆菌菌株对玉米螟毒力的初步评比

本文以玉米螟为供试昆虫,采用规范化的生物测定方法对全国各地筛选的19个高毒力苏芸金杆菌菌株进行毒力评比.实验结果表明属于血清型H_(3a3b)的各菌株对玉米螟具有较高的毒力.以LD_(50)作为衡量各菌株的毒力指标选出了HD-1、鄂农3号、551和80-1等几个高毒力的菌株,为今后生产高效的苏芸金杆菌制剂提供了依据.     

甲氨基阿维菌素苯甲酸盐对3种鳞翅目害虫与赤眼蜂的毒力

摘 要：为明确甲氨基阿维菌素苯甲酸盐对甘肃河西地区3种玉米害虫和松毛虫赤眼蜂的毒力,协调甘肃河西地区化学防治和生物防治之间的矛盾,本研究在室内采用饲喂法和药膜法分别对棉铃虫、亚洲玉米螟、粘虫和松毛虫赤眼蜂进行毒力测定。结果表明,随着甲氨基阿维菌素苯甲酸盐浓度增加,4种昆虫的校正死亡率均呈递增趋势,当药剂浓度达0.500 mg/L时,4种昆虫的校正死亡率均达95%以上。致死中浓度表明,甲氨基阿维菌素苯甲酸盐对松毛虫赤眼蜂毒力最高,致死中浓度LC50为0.078 mg/L,其次依次为亚洲玉米螟、棉铃虫和粘虫,致死中浓度LC50依次为0.109、0.120、0.127 mg/L。甲氨基阿维菌素苯甲酸盐对松毛虫赤眼蜂的毒力是其他3种鳞翅目昆虫的1.40~1.63倍。因此,综合防治中使用甲氨基阿维菌素苯甲酸盐防治害虫时,应避开赤眼蜂的出蜂时期,以降低化学杀虫剂对赤眼蜂的杀伤作用。     

棉铃虫核型多角体和质型多角体在宿主昆虫继代后的毒力分析与比较

以３龄健康棉铃虫幼虫为供试昆虫，测定棉铃虫核型多角体和质型多角体在幼虫体内分别连续继代后的毒力变化。就质型多角体而言，不论是病毒的致死剂量（ＬＤ）还是致死时间（ＬＴ）均随着继代次数的增加而升高，继代１０次后的病毒致死活性平均丧失５９．３％，与未经继代的病毒相比．ＬＤ＿（５０）增加１０３倍，ＬＴ＿（５０）平均延长４．４３５ｄ；而核型多角体在继代过程中的毒力未见显著变化，提示核型多角体与质型多角体在宿主昆虫内连续继代的遗传学行为有可能不同。     

蝉蜕诱导对球孢白僵菌生物学特性及其毒力影响的研究

利用改良蝉蜕诱导培养基对球孢白僵菌进行诱导,以无蝉蜕PDA培养基作为对照,目的是比较蝉蜕诱导后球孢白僵菌菌株的生长速率、产孢量、孢子萌发率等多个生物学指标,及二者对3龄亚洲玉米螟幼虫的毒力。经蝉蜕诱导的球孢白僵菌菌株的产孢量、孢子萌发率以及对玉米螟幼虫毒力都高于对照组,且差异显著,对玉米螟幼虫毒力处理组LT₅₀为4.73天,对照组需要6.97天。同时经蝉蜕诱导过的菌株开始产孢时间和胞外蛋白酶活性都优于对照组,胞外蛋白酶活性的变化范围是1.497×10^-2~3.538×10^-2 IU/mL,但经诱导菌株的生长速率低于处理组。鉴于球孢白僵菌菌株经蝉蜕诱导后,其产孢量和孢子萌发率增加,并且能够增强对玉米螟幼虫毒力,可利用其进行球孢白僵菌菌种保存和改良。

     

用亚洲玉米螟测定苏芸金杆菌制剂毒力效价的研究

利用亚洲玉米螟对苏芸金杆菌的毒力效价进行了测定.供试虫以玉米螟二龄幼虫为佳.用候选苏芸金杆菌制剂与半人工混合饲料混合接虫感染的方法作毒力效价测定,结果准确,操作方便,完成一次测定需时三天,标准差为15.49%.     

21个稻瘟菌株毒力与42个水稻品种抗瘟性的系统聚类分析

通过对42个水稻品种进行人工离体叶片接种,明确供试水稻品种对21个稻瘟菌株的抗普和病级并在此基础上对42个水稻品种抗瘟性作了初步研究。分别按供试21个稻瘟菌株毒力差异和42个水稻品种抗瘟性的多个抗性指标进行系统聚类分析。将供试稻瘟菌株分为七类,其菌株毒力差异显著,菌株毒性频率和平均毒力之间呈现高度负相关。把水稻品种分为七类,其中第三类的第一组抗性最好,抗普在85%~100%,病级4.0以下。结果对选育水稻抗瘟新品种、合理布局区内抗性水稻和防治稻瘟病爆发具有一定的实际意义。     

溴氰虫酰胺对3种鳞翅目害虫的毒力作用比氯虫苯甲酰胺好

<正>为比较溴氰虫酰胺和氯虫苯甲酰胺对甜菜夜蛾、玉米螟和小地老虎的作用差异,山东农业大学植物保护学院科研人员近期采用浸卵法、浸叶法、饲喂毒营养液法等,测定了溴氰虫酰胺和氯虫苯甲酰胺对3种害虫的卵、3龄幼虫和成虫的毒力,以及对其3龄幼虫的拒食活性。结果表明,溴氰虫酰胺和氯虫苯甲酰胺均无杀卵作用,但能降低初孵幼虫存活率。溴氰虫酰胺对甜菜夜蛾、玉米螟和小地老虎3龄幼虫的LC50值分别为0.11、     

提高苏云金杆菌对棉铃虫毒力的研究

在含有Ｂｔ毒素的人工饲料中,通过加入碱性化合物提高其对昆虫中肠的作用,或加入蛋白酶激活剂、无机化合物和有机来提高Ｂｔ的毒力效价。试验结果表明,加入碳酸钙、硫酸锌、氯化镁、苹果酸、马来酸、甲酸和巯基乙醇酸钠,可使Ｂｔ毒力效价分别提高０．９５１．２２,０．３７,０．４７,１．１７,２．１０和９．０倍,其中加入硫酸锌、甲酸和巯基乙醇酸钠的增效效果较好。     

黑白花奶牛发情周期血液中促卵泡素、促黄体素、促乳素、孕酮、雌二醇的含量及变化规律

用放射免疫测定法测定了７头黑白花奶牛发情周期血液中５种生殖激素的含量。ＦＳＨ：平均值８．９０±２１．６８ｎｇ／ｍｌ，第１天２．３４±１．４９ｎｇ／ｍｌ，之后处于低水平，８天出现高峰２８．５８±６４．４５ｎｇ／ｍｌ；ＬＨ：平均值４．１３±１０．６８ｎｇ／ｍｌ，发情后１２ｈ最高２９．１５±１６．６２ｎｇ／ｍｌ，之后处于低水平；ＰＲＬ：平均值２０．４５±１２．００ｎｇ／ｍｌ，全周期变化较大，１天出现高峰４３．１±２８．６２ｎｇ／ｍｌ，６天和１４天有两个较高的峰３５．４３±３１．３３ｎｇ／ｍｌ和３４．８８±２７．５８ｎｇ／ｍｌ；Ｐ４：平均值２．９６±１．８５ｎｇ／ｍｌ，全周期变化不大，０天２．７０±１．３３ｎｇ／ｍｌ，８～１２天形成台状峰３．０１～３．６３ｎｇ／ｍｌ，１５天再出现一峰，遂下降至发情；Ｅ２：全周期处于低水平，发情后１２ｈ最高２３．２３±１７．３１ｐｇ／ｍｌ，遂下降，至５天、９天升高，出现两个峰。了解了５种激素的基础数据及它们之间的消长、协同关系     

光波和光强对几种重要农业害虫趋光性的影响

为探明几种常见农业害虫的趋光行为间的差异,以及为灯光诱捕器类产品研发改进提供理论依据,通过室内比较研究在不同波长或光强的荧光灯刺激下,几种常见农业害虫的趋光行为,结果表明：（1）在CK光源(335.09~359.95 nm,408.66~432.83 nm),灯诱距离为1 m的条件下各种昆虫的趋光率的高低次序为：棉铃虫Helicoverpa armigera (Hübner)＞斜纹夜蛾Prodenia litura (Fabricius)＞粘虫Leucania loreyi (Duponchel)＞朽木夜蛾Axylia putris (Linnaeus)＞喙丽金龟Adoretus sinicus (Burmeister)＞小地老虎Agrotis ypsilon (Rottemberg)＞稻纵卷叶螟Cnaphalocrocis medinalis (Guenée)＞鳃金龟Holotrichia lata (Brenske)＞甜菜夜蛾Spodoptera exigua (Hübner)。（2）20种不同波长光源中4个光源对棉铃虫诱集率较高。（3）在CK光源3个不同水平的光照度条件下(1.18、0.6、0.24 lx),棉铃虫、斜纹夜蛾和鳃金龟都表现出趋光率随光强增强而增高的趋势。（4）棉铃虫、斜纹夜蛾和鳃金龟都在19:30—20:30和22:45—次日7:00 2个时间段内趋光率最高。（5）采用CK光源在室外灯诱的鳞翅目昆虫中,雄虫数量明显高于雌虫,且雌虫有较高的携卵率;蓝紫色光波能够引诱更多的昆虫,而绿色或黄绿色的光波引诱效果不佳。     

Blood,timber, and the state in West Kalimantan,Indonesia

Abstract: West Kalimantan (West Borneo) has a history of violent communal conflict.¹ It also has extensive forests that have been looted for decades. The argument will be that these two are linked, but not by the grievances of the forest dwellers. Except in its first few days, the two main episodes of 1997 and 1999 were not driven mainly by grievances among marginal groups. Rather, explanations based on the ‘resource curse’ carry more weight. These focus attention on the contested nature of the state, rather than on rebellious activities of marginal groups. When state institutions were thrown into disarray by the sudden resignation of President Suharto in 1998, Dayak militants already close to state power rewrote the rules of local politics by demonstratively ‘cleansing’ certain areas of an unpopular immigrant minority. This theatrical manoeuvre impressed political rivals sufficiently to allow Dayaks to gain control over several timber‐rich districts, which had a thriving black economy. Malays later imitated these techniques to stem the tide.     

Helminth parasites of the digestive tract of the oystercatcher,Haematopus ostralegus,in the Wadden Sea,The Netherlands

The digestive tracts of 90 oystercatchers (equal numbers of males and females and of juveniles, subadults and adults) wintering in the Dutch Wadden Sea were examined for helminth parasites. The nematodes Capillaria sp. (36.7%) and Streptocara crassicauda (7.8%) were found in the stomach. Unidentified cestodes (76.7%) and the trematodes Psilostomum brevicolle (42.2%), Notocotylus sp. (81.1%), and unidentified gymnophallids (100%) were found in the intestine and caeca. Two birds were infected with Gymnophallidae only, while all other birds contained additional helminth species. Compared with subadult and adult birds, the juveniles had significantly more infections with Capillaria sp. and cestodes. Moreover, the juveniles were infected with a greater variety of species. No further relation was found between the presence of helminths or worm numbers and age groups or sexes of birds.     

The inheritance of resistance to the blossom weevil, Anthonomus rubi, in the cultivated strawberry, Fragaria×ananassa

The objective of this research was to determine which strawberry germplasm could be used to combine late flowering with reduced susceptibility to the strawberry blossom weevil, Anthonomus rubi. Seven cultivars and three breeding lines were compared for their susceptibility to A. rubi, by introducing adult weevils onto detached inflorescences. No consistent differences were detected but this contradicted observations from field trials. Five late‐flowering strawberry genotypes were crossed in a half‐diallel programme and progeny were tested for their susceptibility to A. rubi by using detached inflorescences and in a field trial where plants were exposed to a natural infestation. There was good correspondence between the results from the two methods and heritable differences were detected in both experiments, with the additive genetic variance being the more important. The cultivars ‘Idea’ and ‘Alice’ were identified as promising parents for reduced susceptibility while progeny from ‘Sophie’ were most likely to be susceptible.     

Urbanization,interregional accessibility,and the decision to migrate

Trends in population and labor force growth in nonmetropolitan areas of the United States during the 1970s are analyzed. The authors investigate the relationships among migration behavior, urban accessibility, and externalities such as congestion that are associated with urban residence. "A model of the migration decision [is examined] that incorporates in an explicit fashion this proximity-centrality relationship. Estimates of the model are also discussed, with specific attention given to the relationship under question. In addition, the age selectivity of the relationship [is] examined. Insights on the nonmetropolitan reversal drawn from the model estimates are discussed in a third section, followed by concluding remarks."     

Transport Costs,the New Economic Geography,and Rural Development

This paper explores land use conflicts between non-farm neighbors and farmers to illustrate the usefulness of the concepts of interdependence, rules, and property rights when doing rural development. Recognizing interdependence and its implications helps economic analysis focus on and understand the types of rules and institutions having the most influence on economic behavior, and thus identify policy alternatives. The resolution of land uses conflicts, for example, unavoidably changes the bundle of rights associated with land, and influences who can impose costs of whom; it makes a difference if a large farm has the right to produce odors, flies, or noise that reduces their neighbors' abilities to enjoy the neighbors' own land, or if instead, neighbors have the right to use their property without experiencing farm-produced odors, flies or noise the farm may be unable to use its own land for agriculture without being inconvenienced.     

“三农”问题的核心、症结及解决途径

农村、农业、农民问题，是一个影响现代化进程的难题，同时也是一个重大的经济、政治和社会问题。我国的“三农”问题，由于特殊国情所致，与其他国家相比，表现得更为尖锐，解决起来难度更大。深入探索“三农”问题的有效解决途径，乃为当前急需研究的重大课题。