ECOLOGY U1 有害生物问题及其防治对策new

Chemical toxicity 化学毒性
Most chemical pesticides are toxic to a range of organisms, beyond the target pest species. Insecticides are particularly problematic, many affecting a wide range of vertebrates and invertebrates. The impact on nontarget species can cause ecological, economic and human health problems. Herbicides are often fairly unspecific in their action, and some may also be mammalian toxins. 大多数化学杀虫剂对一系列有机体有毒，超出了目标有害 生物物种。杀虫剂是特别有问题的，很多的杀虫剂影响了 广泛的脊椎动物和无脊椎动物。对非目标物种的冲击，能 够引起生态的、经济的和人类健康问题。除草剂的作用经 常是相当无特异性的，有些也可能毒害哺乳动物。
Evolution of resistance 抗性进化
Evolved resistance to pesticides represents a serious threat to agricultural production. Pesticide resistance provides some of the best examples of evolution in action. Within a large population exposed to pesticide, a few genotypes may be unusually resistant and will possess a huge evolutionary advantage. 有害生物对杀虫剂产生了进化抗性，使农业生产受到严 重威胁。杀虫剂的抗性提供了一些当前作用中的最好进 化例证。暴露到杀虫剂中的一个巨大种群内，只有很少 的基因型可能有特异的抗性，并具有极大的进化优势。
U2 PESTICIDES AND PROBLEMS
杀虫剂和问题
Key Notes要点
Chemical insecticides and herbicides 化学杀虫剂和 除莠剂 Inorganic compounds were traditional herbicides, but due to problems with persistence and nonspecificity, compounds such as borates and arsenicals are rarely used. Chemical pesticides are generally used to treat a particular insect pest at a particular location. However, problems arise because these chemicals are toxic to other animals, and because many chemicals persist in the environment. 无机化合物是除草剂的惯用试剂，但由于具有持久性和 非特异性的问题，如像硼酸盐和含砷制剂的化合物是极 少应用的。化学杀虫剂一般用于处理特殊地点上的特殊 害虫。可是问题出现了，因为这些化合物对其他动物是 有毒的，并且很多化学物持续存在于环境中。
Biomagnification 生物放大作用
A further problem arises, particularly, in the use of chlorinated hydrocarbons, because of their susceptibility to biomagnification. Because these toxins cannot be metabolized or destroyed, they accumulate in the body of an individual. This results in an increasing concentration of insecticide in organisms at the higher trophic levels. These effects threaten natural predator predator populations and may pose a risk to the human food chain (especially if fish are affected). 进一步的问题出现了，特别是在使用氯化烃中，这是由 于它们对生物放大作用的灵敏性。由于它们的毒素不能 代谢，或者不能被破坏，它们就累积在个体的体内。这 就导致在更高营养级上的有机体中，农药的浓度增加。 这些效应威胁了自然的捕食者种群，并可能对人类食物 链形成危险（尤其是当鱼受到影响时）。
U1 THE PEST PROBLEM AND
CONTROL STRATEGIES 有害生物问题及其防治对策
Key Notes 要点
What is a pest? 有害生物是 什么？ Pests compete with humans for food of shelter, transmit pathogens, feed on humans or otherwise threaten human health, comfort or welfare. Weeds may be included in this definition. One of the most important characteristics of pests is the high degree to which they are normally regulated by their natural possibly due to their importation to new regions of the world. 有害生物和人类竞争食物或空间、传播病原体、以人为食， 或用不同方法威胁人类健康、舒适或安宁。野草可能包括在 这个定义内。有害生物最重要特征之一，是它们通常被它们 的天敌调节到高的水平。有害生物是经常能逃避它们天敌的 物种，可能是由于它们迁入世界新的地区。
The aim of pest control 有害生物防治目标
Although in some instances the aim of pest control is to eradicate the pest species, generally the aim of pest control is to reduce the pest population to a level at which on further reductions are profitable. This is known as the economic injury level (EIL) for the pest, or if social and amenity benefits are included, the aesthetic injury level (AIL). In the case of disease, total eradication can be justified on the basis that the saving of one single life far exceeds any economic costs. In practical pest control ,the EIL is not as important as the control action threshold (CAT) – the pest density at which action should be taken in order to prevent an impending pest outbreak. 尽管在有些情况下，有害生物防治的目标是根除有害生物 种，然而通常有害生物的防治目的总是降低有害生物种群 到一个水平上，在这个水平上进一步降低是无利可图的。 这被称为有害生物的经济损害水平（EIL），如果考虑到社 会的和环境的舒适利益，或许它被称为美学损害水平 （AIL）。就疾病而言，根除全部有害生物能够被认为是有 理的，这是基于救活一个人远超过任何经济的价值。在实 践有害生物的防治中，EIL不像防治活动阈值（CAT）那样 重要，在经济活动阈值这个有害生物密度上，其作用应该 被理解是阻止即将来临的有害生物的爆发。
Types of pest contro 有害生物防治类型
Approaches to limit pest damage to food crops have been adopted for thousands of years, particularly using cultural control (e.g.altering the sowing date or avoiding repeatedly replanting the same crop in the same place). Biological control (the use of natural enemies – predators and parasites) has also had a long history. This century, chemical control became a key approach, although there are serious toxicity and other problems. The development of pest – resistant crop varieties is another valuable strategy. 限制有害生物损伤粮食作物的方法已被采用数千年，特别 是用于栽培防治（例如改变播种日期、或避免在同一地区 重复种植相同的作物）。生物防治（利用天敌——捕食者 与寄生物）也具有悠久的历史。本世纪以来，化学防治变 成主要的途径，尽管存在着严重的毒性和其他一些问题。 抗有害生物的作物品种的培育是另一类有价值的对策。