下面雅思为大家整理了一篇关于生物技术防治病虫害的雅思阅读真题题源。这篇雅思阅读真题题源的主要内容是生物技术防治病虫害的应用原理,应用过程,以及想ing的作用。但是大家也要注意使这个生物技术应用的恰到好处才行。
A. Biological control is, generally, humans use of a specially chosen living organism to control a particular pest. This chosen organism might be a predator, parasite, or disease which will attack the harmful insect. It is a form of manipulating nature to increase a desired effect. A complete Biological Control program may range from choosing a pesticide which will be least harmful to beneficial insects, to raising and releasing one insect to have it attack another, almost like a living insecticide.
B. Biological control methods can be used as part of an overall Integrated Pest Management program to reduce the legal, environmental, and public safety hazards of chemicals. In addition, it may be a more economical alternative to some insecticides. Some biological control measures can actually prevent economic damage to agricultural crops. Unlike most insecticides, biological controls are often very specific for a particular pest. Other helpful insects, animals, or people can go completely unaffected or disturbed by their use. There is less danger of impact on the environment and water quality.
C. Biological control takes more intensive management and planning. It can take more time, require more record keeping, more patience, and sometimes more education or training. Successful use of biological control requires a greater understanding of the biology of both the pest and its enemies. Many natural enemies are very susceptible to pesticides, and using them successfully in an IPM program takes great care. In some cases, biological control may be more costly than pesticides. Often, the results of using biological control are not as dramatic or quick as the results of pesticide use. Most natural enemies attack only specific types of insects unlike broad-spectrum insecticides, which may kill a wide range of insects. Though often an advantage, this can also be a disadvantage.
D. Biological control uses naturally occurring predators, parasites and diseases to control pests. There are three main ways to use these natural enemies against unwanted insect pest populations. Classical Biological Control involves traveling to the country or area from which a newly introduced pest originated and returning with some of the natural enemies that attacked it and kept it from being a pest there. New pests are constantly arriving accidentally or intentionally. Sometimes they survive. When they come, their enemies are left behind. If they become a pest, introducing some of their natural enemies can be an important way to reduce the amount of harm they can do. Augmentation is a method of increasing the population of a natural enemy which attacks a pest. This can be done by mass producing a pest in a laboratory and releasing it into the field at the proper time. Another method of augmentation is breeding a better natural enemy which can attack or find its prey more effectively. Mass rearings can be released at special times when the pest is most susceptible and natural enemies are not yet present, or they can be released in such large numbers that few pests go untouched by their enemies. The augmentation method relies upon continual human management and does not provide a permanent solution unlike the importation or conservation approaches may. Conservation of natural enemies is an important part in any biological control effort. This involves identifying any factors that limit the effectiveness of a particular natural enemy and changing them to help the beneficial species. Conservation of natural enemies involves either reducing factors which interfere with the natural enemies or providing needed resources that help natural enemies.
E. In addition to the introduction of predators, several microbial pathogens are effective against nematodes. They consist of a microorganism as the active ingredient. They can control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest . For example, there are fungi that control certain weeds, and other fungi that kill specific insects. The most widely used microbial pesticides are subspecies and strains of Bacillus thuringiensis, or BT. Each strain of this bacterium produces a different mix of proteins, and specifically kills one or a few related species of insect larvae. While some BTs control moth larvae found on plants, other BTs are specific for larvae of flies and mosquitoes. The target insect species are determined by whether the particular BT produces a protein that can bind to a larval gut receptor, thereby causing the insect larvae to starve.
沪教牛津版小学英语一年级上册 Unit3 period1教案
外研版一年级英语上册教案Unit1 Hello
沪教牛津版一年级英语上册教案Unit1 My classroom第二课时
上海牛津版一年级英语下册Unit2 Small animals第五课时教案
一年级英语上册Unit1 My classroom第三课时教案
上海牛津版一年级英语下册Unit2 Small animals教案
沪教版小学英语一年级下册教案unit1课时4
牛津版一年级英语上册教案Unit4 My bag第一课时
一年级英语上册教案 Unit1My classroom 第三课时
一年级英语上册教案Unit1 My classroom第一课时教案
新起点小学一年级英语下册Unit11 Toys教案
一年级英语教案Module1 unit6 Mid-Autumn Festival
牛津版一年级英语上册Unit 2 Good morning 教案
沪教牛津版小学英语一年级上册 unit9 教案
沪教版小学英语一年级下册教案unit1课时3
一年级英语上册Unit8 Playtime 第三课时教案
牛津版一年级英语上册unit5 Fruit教案(3)
上海牛津版一年级英语Unit2 Small animals第四课时教案
沪教版小学英语一年级下册教案unit1课时5
上海牛津版一年级英语下册教案Unit9 Revision(3)
沪教牛津版小学英语一年级上册 Unit 8 教案
一年级英语下册Unit2 Small animals第三课时教案
上海版牛津一年级英语教案 Unit 3 My abilities
上海牛津版一年级英语下册Unit9 Revision第一课时教案
新课标小学英语第一册期末考试百词范围
一年级英语Module1 unit6 Mid-Autumn Festival教案
上海牛津版一年级英语下册Unit3 Colours教案(1)
新起点小学一年级英语教案Unit7 Fruit
苏教版小学一年级英语下册Unit5 On the road教案
牛津版小学一年级英语上册Unit1 Hello教案
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |