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881.
882.
Simon R. Leather 《Integrated Pest Management Reviews》1996,1(3):163-180
The ecological implications of insect resistance in conifers are rarely discussed. It is however a fairly straightforward plant-insect interaction and should be treated as such, making use of the increasing amount of information in this field. Work on tree breeding is usually carried out by silviculturalists who, not surprisingly, rarely consider the insect component of the environment in which the treess are growing. In all fairness, it must be stated that many entomologists, fail to consider the plant component of the interaction. Clonal forestry will almost certainly result in the loss of genetic variability. The use of clonal material has already been cited as a possible source for the diminution of the resistance against pests and diseases and if particular resistance mechanisms against forest pests are sought in the future the reduction in genetic material caused by clonal selection could have serious consequences. The ethics of clonal forestry have been questioned as have the ethics of biotechnological advances in the area of recombinant DNA molecules. The potential of both these techniques should be publicized and brought to the attention of the general public and the scientific community at large and evaluated. To improve our forest environment and to protect the environment as a whole, entomologists, geneticists, physiologists and silviculturalists must work together to produce better trees that require little, if any, chemical aid, be it insecticides, herbicides, fungicides or fertilizers. An increasing awareness of the environmental problems generated by large-scale insecticide applications to forest plantations, coupled with an increasingly chemophobic work-force and the difficulty in obtaining pesticide registration for use in forest environments, means that the forest industry world-wide must look to the use of integrated control measures with more diligence than has been shown in the past. Many recent outbreaks of pests and diseases have been linked with particular seed origins of tree crops. Host plant resistance as part of a suite of other proposed integrated control tools is thus an obvious candidate for development. Despite this, scientists concerned with tree improvement continue to select largely for silvicultural traits rather than for resistance to pests and disease. The different avenues open to plant breeders are examined and the potential of breeding trees resistant to insect attack highlighted. Using resistant trees as part of an integrated pest management system has five very important properties. Firstly, there is no additional pest control cost to the grower, secondly, it operates at all levels of insect incidence and not just when the pest is at high population levels, thirdly, it reduces the insect population cumulatively, fourthly it avoids toxic residues and environmental pollution and, finally, it usually interacts well with the other integrated pest management strategies in existence. 相似文献
883.
宁夏盐池县沙边子试验基地生态效益评价 总被引:4,自引:0,他引:4
本文简要总结了沙边子试验基地九年来所做的主要工作,同时试用模糊数学方法采用三类评价指标17个评价因子对基地整治前(1982年)和整治后(1990年)的生态效益给予综合对比评价。 相似文献
884.
昆虫病原斯氏和异小杆线虫人工大量培养的研究概况 总被引:3,自引:0,他引:3
昆虫病原斯氏和异小杆线虫的大面积田间应用要求线虫有效地生产,本文介绍业已建立线虫大量培养方法及合适于大规模生产线虫的工厂化培养系统及有关的技术参数,并讨论其优化管理问题。 相似文献
885.
A case study of forest change in the Swiss lowlands 总被引:2,自引:0,他引:2
This paper presents a regional case study of forest development and the history of forest use and management in the north-eastern lowlands of Switzerland during the 19th and 20th centuries. The analysis draws on historical documents related to forestry to consider the following aspects of forest change: forest types, growing stock, trees species composition and non-timber forest uses. Based on the data presented, three overlapping periods of forest use and management can be discerned. The period of traditional multiple use lasted until the second half of the 19th century. From the mid 19th to the mid 20th century, a period of primacy of timber production occurred. During the 20th century, the period of modern multi-impact management has developed. For these three periods, groups of main actors, their needs and interests, and how they were causing the changes in the aspects under study were defined. This procedure of defining periods and the respective groups of main actors is a critical link between landscape ecology and history, as changes in demands of the society can be directly linked with changes in land-use and land-cover. 相似文献
886.
Pluimers FH de Leeuw PW Smak JA Elbers AR Stegeman JA 《Preventive veterinary medicine》1999,42(3-4):139-155
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. 相似文献
887.
Sixty of the 65 dairy farms with cubicle houses in the Norwegian county of Oppland were included in a field study of the management of calving in 1990. The farmers recorded the location of the cow when giving birth, farmer presence and whether assistance was given during calving, occurrence of suckling, and time after birth when cow and calf were separated. Such data were recorded for a total of 1125 calvings. About 10% occurred on pasture, while 78% of the remaining calvings took place in the cubicle-equipped section. Thirteen percent calved in a calving pen, the remaining cows being tethered at the time of calving. Thirty-two percent of the calvings took place in houses lacking a calving pen altogether. Farmers were present during 41% of the calvings. Suckling most frequently occurred after pasture calvings, and was least frequent after calvings within the cubicle-equipped section of the cowhouse. Injuries to the calf caused by trampling or contact with fittings etc. were rare, and no more common in association with calving in the cubicle-equipped section than with calving taking place with the cow isolated from the rest of the herd. All calves were removed from their dams within 24 h after birth. 相似文献
888.
889.
890.
中国北方草原畜牧业限制因素以及管理策略分析 总被引:1,自引:0,他引:1
根据对内蒙古一个有关草地保护和管理项目的调研,分析了影响草原资源可持续利用和草原畜牧业发展的一些限制因素。调研发现,草原地承包及租赁体制、饲草料生产和供给策略、家畜放牧制度等是影响本地区畜牧业生产体系和草原可持续性的主要因素。基于本研究结果,提出了“春季休牧”(或称之为“延迟放牧”)的生产方式。同时,推荐了一些可缓解冬春季节严重饲草料不足的措施。 相似文献