练习说明
段落填空 题目要求： 阅读文段，从文中挑选原词补全句子，每道题目都有特定的字数要求，以黑体加粗字标示。请把答案填到每题空缺处。
Questions 1 一 7
Complete the notes below.
Choose ONE WORD ONLY from the passage for each answer.
Write your answers in boxes 1-7 on your answer sheet.
原文
In the north of Australia there arc many sugar cane plantations, which early in the 20th century were being damaged by a particular pest. This was a species of beetle whose larvae, the infant form of the beetle, live underground in the soil in the sugar cane fields. The sugar cane plants were weakened or died because their roots were eaten by the larvae. This had serious economic consequences for sugar cane farmers. Modern pesticides were not developed until the 1940s, so farmers had to use what was available at the time. Chemicals like arsenic and copper were used, but these were not only expensive but also stayed in the environment and were poisonous to people, plants and animals. It was generally acknowledged by government, farmers and scientists that cheaper and safer methods of pest control had to be found.
A promising replacement for copper and arsenic was the use of biological control. Farmers already used some forms of biological pest control in the form of predatory and parasitic wasps and flies, insect-eating birds, and plants from different regions or countries to control pests. Common practice was to release these introduced agents into new environments, the expectation being that they would destroy resident pests. Some species of toad already had successful records as agents of biological control in gardens. For example, in 19th-century France toads were sold to gardeners at markets in Paris to eat insect pests in their gardens. In the early 20th century French sugar cane farmers first took giant toads from South America to control pests in their Caribbean sugar cane plantations. Although there is no evidence that these toads did help to control pests, sugar cane scientists then carried some of these toads from Jamaica and Barbados to Puerto Rico and from there to Hawaii.
The idea of biological control of pests was not new to Australia. For example, in 1926 there had been a highly successful prevention of the increase of the exotic prickly-pear cactus by the introduction of a moth from Argentina. This success added strength to the argument that biological control was the answer to the sugar cane industry's pest problems. Accordingly, in the early 1930s a decision was taken to introduce the giant South American toads, which in Australia are now commonly called cane toads, into Australian sugar cane plantations.
In 1935, an Australian entomologist brought 101 cane toads from Hawaii and released them in sugar cane plantations in the north of Australia. However, over the following years it became clear that the cane toads were a failure. There was a fatal flaw in the plan to use them as a form of biological control. This was that earthbound cane toads were expected to eat the mostly flying adult beetles in order to eliminate the soil-dwelling beetle larvae that ate the roots of the cane sugar plants. This, of course, cane toads could not do.