# Biological control of pests: answers and explanations

Cambridge IELTS 8, Test 4, Reading Passage 2

Source: Passage, questions and answer key from Cambridge IELTS 8, Test 4, Reading Passage 2. © Cambridge University Press & Assessment. Used for educational practice. Explanations and evidence notes are written by Testmigo.

## Answer key

| Q | Answer | Proof |
| --- | --- | --- |
| 14 | B | Apart from engendering widespread ecological disorders |
| 15 | A | more than 300 species of agricultural pests have developed resistance to a wide range of potent chemicals. |
| 16 | D | the farmers avidly took to pesticides as a sure measure to boost crop yield. |
| 17 | D | 50% of the financial outlay on cotton production was accounted for by pesticides. |
| 18 | NOT GIVEN | Not to be left behind are the disease-spreading pests, about 100 species of which have become immune to a variety of insecticides now in use. |
| 19 | YES | bear offspring with a built-in resistance to pesticides. |
| 20 | NO | involving the selective use of natural enemies of the pest population |
| 21 | YES | When handled by experts, bio-control is safe, non-polluting and self-dispersing. |
| 22 | D | parasites that prey on 'disapene scale' insects - notorious defoliants of fruit trees in the US and India. |
| 23 | H | Neodumetia sangawani, was found useful in controlling the Rhodes grass-scale insect |
| 24 | C | when Sri Lanka's flourishing coconut groves were plagued by leaf-mining hispides |
| 25 | E | is now trying out an Argentinian weevil for the eradication of water hyacinth |
| 26 | B | About 30,000 hectares of rice fields in Kerala are infested by this weed. |

## Why these answers are right

**14. B.** The question asks what pesticide use has contributed to. The first paragraph says pesticides have engendered widespread ecological disorders as well as resistant superbugs. Widespread ecological disorders means an imbalance in ecologies around the world, so B is correct.

**15. A.** The question concerns the 300 agricultural pests counted by the FAO. The passage says these species have developed resistance to a wide range of potent chemicals. Being resistant means they no longer respond to most pesticides, which matches A.

**16. D.** You need the reason cotton farmers started using pesticides. In the early 1940s they took to pesticides as a sure measure to boost crop yield. Boosting yield means harvesting more cotton from each crop, so D. The chemical-resistant pests came later, in the 1950s.

The why and the trap for questions 17 onwards are free with an account on the [answers page](https://testmigo.com/ielts/reading/biological-control-of-pests/answers).

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