上海PMWS并发PRRS自然病例的病理组织学观察

对上海5例5～13周龄断奶仔猪多器官衰竭综合征（PMWS）并发猪繁殖与呼吸综合征（PRRS）自然病例进行了病理组织学观察。结果：5例病猪均出现坏死性淋巴结炎、间质性肺炎以及不同程度的坏死性脾炎、间质性肾炎和肝炎。2例病猪出现心肌炎，表现为心肌纤维断裂、溶解和心肌间质中淋巴细胞局灶性浸润。2例病猪出现脑炎，在大脑白质区出现神经胶质细胞结节。     

蛋鸡中发现J亚群白血病与网状内皮增生症自然混合感染

发病蛋鸡经组织学、免疫组化检测确诊为J亚群白血病与网状内皮增生症混合感染。与人工接种病例不同的是，在肿瘤组织内还发现一种特殊的细胞——淋巴-巨噬细胞；在骨髓和肿瘤组织中检测到部分髓细胞胞浆内有ALV—J抗原表达。从发病情况、各器官病变程度及免疫组化结果来看，2种病原存在明显的相互协同作用，脾可能是网状内皮增生症的原发器官。但其发病的时间可能不如J亚群白血病早。此次在蛋种鸡发现此混合感染提示，病毒在环境选择压及免疫选择压的作用下，其生物特性、致病作用以及宿主范围均可发生改变。应警惕J亚群白血病和网状内皮增生症混合感染在蛋鸡中的大面积暴发。     

氮肥对水稻叶冠层捕食性天敌种群及其自然控制能力的影响

为了公正地评价氮肥对整个稻田生态系统的影响，在国际水稻研究所试验场分别设立0、100和200kg／hm^2三个氮肥水平，测定了水稻主要特性参数和叶冠层捕食性天敌的种群动态，同时以果蝇蛹作为替代猎物的方法在田间模拟评价了叶冠层捕食性天敌对害虫的自然控制能力。结果表明，虽然施用200kg／hm^2氮肥稻田的稻株高度、叶面积和稻草干重显著比施用100kg／hm^2氮肥稻田的高，但每丛分蘖数和稻谷产量则没有明显差异。在水稻叶冠层中，肖蛸、圆蛛、黑肩绿盲蝽、稻红瓢虫和捕食性螅等为稻飞虱主要捕食性天敌。肖蛸在水稻孕穗期的数量最高，圆蛛的种群随水稻的生长而下降，但黑肩绿盲蝽、稻红瓢虫和捕食性螅的数量却均随水稻的生长而增加。施用氮肥后稻田中肖蛸和稻红瓢虫的种群数量显著减少。在水稻孕穗期，叶冠层上蜘蛛网的数量和蜘蛛网总面积均随氮肥施用量的提高而显著减少。在水稻孕穗期和乳熟期，不施用氮肥稻田中的捕食性天敌对替代猎物果蝇蛹的捕食能力显著高于其它两个施用氮肥的稻田中的捕食能力。而在乳熟期施用100kg／hm^2氮肥稻田的捕食能力又显著比施用200kg／hm^2氮肥稻田的高。结果说明过量施用氮肥可削弱天敌对害虫的自然控制作用。     

新疆莎车县棉田自然天敌数量动态

2002-2004年研究了新疆莎车县棉田节肢动物类自然天敌种群动态及棉花品种的影响。结果发现节肢动物类自然天敌67种,数量较多的共10类,即瓢虫类、蝽类、隐翅虫类、蓟马类、草蛉类、食蚜双翅目、胡蜂类、蚜茧蜂类、蜘蛛类和捕食螨类。其中瓢虫类、蝽类和蜘蛛类占天敌个体总数85%~93%。3年中这三类天敌各自所占比例,瓢虫为4%~65%,食虫蝽为19%~57%,蜘蛛为6%~34%。瓢虫、食虫蝽和蜘蛛的最高密度2002年分别为237.2、164.0、87.0头/百株,2003年分别为28.3、533.3、232.0头/百株,2004分别为1506.5、237.0、55.3头/百株。对转基因抗虫棉GK19(表达Cry1A杀虫蛋白)、SGK321(表达Cry1A CpTI杀虫蛋白)和普通棉花泗棉3号、石远321的研究表明,各种天敌在不同品种上的种群数量没有显著性差异,而喷施化学农药可以造成天敌数量明显减少。     

象虫金小蜂中国新记录

本文首次报道了象虫金小蜂在中国的分布,并用图文简要地描述其特征。该蜂是四纹豆象、米象、谷象、玉米象、烟草甲和药材甲等重要贮藏物害虫的天敌。     

不同种昆虫病原线虫对同一寄主个体的竞争及对线虫繁殖的影响

采用注射侵染和自然侵染法，测试了长尾斯氏线虫X-7品系、小卷蛾斯氏线虫All品系和嗜菌异小杆线虫H06品系对同一寄主大蜡螟幼虫的相互作用，及其对线虫繁殖的影响。结果表明，无论是注射侵染还是自然侵染法，对大蜡螟幼虫个体的致死竞争能力最强的是长尾斯氏线虫，其次是小卷蛾斯氏线虫，嗜菌异小杆线虫的致死能力最弱。在同一大蜡螟幼虫体内时。异小杆线虫的繁殖受斯氏线虫的不利影响较大，而两种斯氏线虫的繁殖受异小杆线虫的不利影响较小。两种斯氏线虫对各自的繁殖影响不大。     

Population structure of poplar rust Melampsora larici-populina in the UK inferred from AFLP

AFLP profiles were generated from poplar leaf rust ( Melampsora larici-populina ) collected from Populus trichocarpa cv. Trichobel at six sites in the UK in 2001. Of a total of 145 isolates, 121 were unique AFLP phenotypes. On one occasion, the same AFLP phenotype was found at two sites. The analysis indicated that 81·88% of the total variation was attributable to differences among individuals within replicate plots, 3·47% to differences among plots within sites and 14·65% to differences among sites. Weir & Cockerham's θ was calculated as 0·138 and θ ^B , the Bayesian analogue of F _ST, as 0·146. Overall, there was sufficient gene flow among different sites to prevent genetic drift, as Nm was calculated as 1·562 using θ and as 1·462 using θ ^B . Nei's genetic distance and population-assignment test indicated that the rust from a site in north-east England was differentiated from those from other sites. There was no significant correlation between genetic and geographical distances. The results indicate that sexual reproduction has a major influence on the relative lack of population structure of M. larici-populina in the UK.     

美洲斑潜蝇自然种群生命表及飞行能力的研究

美洲斑潜蝇ＬｉｒｉｏｍｙｚａｓａｔｉｖａｅＢｒａｎｃｈ．田间自然种群中,幼虫期的死亡率最高,１、２、３龄幼虫平均死亡率分别为４８．１４％、５０．８６％、７８．９７％,幼虫期被寄生蜂寄生的概率随龄期的增大而增高,从１龄的１．４４％上升到３龄的６０．８８％。应用微型昆虫飞行磨（Ｆｌｉｓｈｔｍｉｌｌ）计算机联机装置对不同日龄成虫的飞行能力进行了测试,结果表明：雌虫飞行能力随日龄的增大而增强,３日龄最大连续飞行的时间为８．８３分钟,距离为２７２．９３ｍ。雄虫以２日龄成虫飞行能力最强,最长的一次连续飞行时间可达２５．００分钟,距离为８８２．８８ｍ。     

The Potential Benefits of Weeds with Reference to Small Holder Agriculture in Africa

Weed control is one of the most important crop protection activities undertaken in both intensive and low-input farming systems. However, even under intensive systems, crop protection which is less dependent on pesticides may require that weeds be managed to obtain a balance between crop and non-crop vegetation to encourage an increase in natural enemies of crop pests. In the low-input farming systems which sustain much of the rural population of Africa, weed control is usually done by hand and clean weeding is often beyond the labour resources of the farming family. The vegetational diversity of peasant agriculture in Africa to which weeds make their contribution, helps to decrease the risk of disease and pest epidemics. In addition to the pest control benefits of a diverse agroecosystem, weeds contribute to the resource base of the rural community, providing a source of secondary foods, medicines and insecticides. Weed control within an integrated crop protection system appropriate to the needs of the resource-poor farmer, requires that weeds are managed in such a way that their biodiversity is maintained and the more useful species retained within the field or field margin. Those weeds with high food potential or which have pesticidal or medicinal properties might be deliberately encouraged within the crop or field margins. Certain weed species may harbour important pests or diseases of local crops and therefore should be selectively removed. The paper reviews and discusses the literature on the beneficial and deleterious effects of weeds and argues for a weed management strategy which balances the effects of weed competition on crop production with the ethnobotanical and pest control attributes of individual weed species and weed communities.     

Epidemiological Observations in a Corriedale Flock affected by Brucella ovis

Brucellosis in sheep, caused by Brucella ovis, is primarily a chronic infectious disease of rams with epididymitis as its most characteristic lesion. Six hundred rams from an infected farm were clinically and serologically examined once a year, over a 3-year period. An increase from 2.1% to 6.3% in the prevalence of animals serologically positive to B. ovis occurred over the 3 years. However, the prevalence of rams with lesions in the reproductive tract declined from 14.2% to 6.5% in the third year following one year of strict culling of clinically affected and rams that were serologically positive for B. ovis. Clinical lesions found in the 179 affected rams fell into two main categories: rams with epididymitis and rams with affected lymph nodes. These results suggest that the prevalence of the disease relates mainly to the sexual activity of the animal and not to age in itself. A single cull based on the results of clinical examination and serological test results was unable to decrease the prevalence of B. ovis in an extensive Corriedale sheep flock.