Table of Contents
Chinese Yellow Citrus Ant for BIOLOGICAL CONTROL
Passage
A. In 1476, the farmers of Berne in Switzerland decided, according to this story, there was only one way to rid their fields of the cutworms attacking their crops. They took the pests to court. The worms were tried, found guilty and excommunicated by the archbishop. In China, farmers had a more practical approach to pest control. Rather than rely on divine intervention, they put their faith in frogs, ducks and ants. Frogs and ducks were encouraged to map up the pests in the paddies and the occasional plague of locusts.
But the notion of biological control began with an ant. More specifically, the story says, it started with the predatory yellow citrus ant is a type of weaver ant, which has been polishing off pests in the orange groves of southern China for at least 1700 years. The yellow citrus ant $0 is a type of weaver ant, which binds leaves and twigs with silk to form a neat, tent-like nest. In the beginning, farmers made do with the odd ants’ nest here and there. But it wasn’t long before growing demand led to the development of a thriving trade in nests and a new type of agriculture—ant farming.
B. For an insect that bites, the yellow citrus ant is remarkably popular. Even by ant standards, Oecophylla smaragdina is a fearsome predator. It’s big, runs fast and has a powerful nip – painful to humans but lethal to many of the insects that plague the orange groves of Guangdong and Guangxi in southern China. And for at least 17 centuries. Chinese orange growers have harnessed these sixlegged killing machines to keep their fruit groves healthy and productive.
The story explains that citrus – a fruits evolved in the Far East and the Chinese discovered the delights of their flesh early on. As the ancestral home of oranges, lemons and pomelos, China also has the greatest diversity of citrus pests. And the trees that produce the sweetest fruits, the mandarins—or kan-attract a host of planteating insects, from black ants and sap sucking mealy bugs to leaf-devouring caterpillars. With so many enemies, fruit growers clearly had to have some way of protecting their orchards.
C. The West did not discover the Chinese orange growers’ secret weapon until the early 20th century. At the time, Florida was suffering an epidemic of: itrus canker and in 1915 Walter Swingle, a plant physiologist working for the US Department of Agriculture, was, the story says, sent to China in search of varieties of orange that were resistant to the disease. Swingle spent some time studying the citrus orchards around Guangzhou, and there he came across the story of the cultivated ant. These ants, he was told, were “grown” by the people of a small village nearby who sold them to the orange growers by the nestful.
D. The earliest report of citrus ants at work among the orange trees appears in a book on tropical and subtropical botany written by His Han in AD 304. “The people of Chiao-Chih sell in their markets ants in bags of rush matting. The nests are like silk. The bags are all attached to twigs and leaves which, with the ants inside the nests, are for sale. The ants are reddish-yellow in colour, bigger than ordinary ants. In the south if the kan trees do not have this kind of ant, the fruits will all be damaged by many harmful insects, and not a single fruit will be perfect.”
E. Initially, farmers relied on nests which they collected from the wild or bought in the market — where trade in nests was brisk. ‘It is said that in the south orange trees which are free of ants will have wormy fruits. Therefore the people race to buy nests for their orange trees,’ wrote Liu Hsun in Strange Things Noted in the South, written about AD 890. The business quickly became more sophisticate. From the 10th century, country people began to trap ants in artificial nests baited with fat. “Fruit growing families buy these ants from vendors who make a business of collecting and selling such creatures,” wrote Chuang Chi-Yu in 1130.
“They trap them by filling hogs’ or sheep’s bladders with fat and placing them with the cavities open next to the ants’ nests. They wait until the ants have migrated into the bladders and take them away. This is known as ‘rearing orange ants’.” Farmers attached the bladders to their trees, and in time the ants spread to other trees and built new nests. By the 17th century, growers were building bamboo walkways between their trees to speed the colonization of their orchards. The ants ran along these narrow bridges from one tree to another and established nests “by the hundreds of thousands”.
F. Did it work? The orange growers clearly thought so. One authority, Chi Ta— Chun, writing in 1700, stressed how important it was to keep the fruit trees free of insect pests, especially caterpillars. “It is essential to eliminate them so that the trees are not injured. But hand labour is not nearly as efficient as ant power…” Swingle was just as impressed. Yet despite this reports, many Western biologists were skeptical.
In the West, the idea of using one insect to destroy another was new and highly controversial. The first breakthrough had come in 1888, when the infant a orange industry in California had been saved from extinction by the Australian vedalia beetle. This beetle was the only thing that had made any inroad into the explosion of cottony cushion scale that was threatening to destroy the state’s citrus crops. But, as Swingle now knew, California’s “first” was nothing of the sort. The Chinese had been expert in biocontrol for many centuries.
G. The story goes on to say that the long tradition of ants in the Chinese orchards only began to waver in the 1950s and 1960s with the introduction of powerful organic (I guess the author means chemical insecticides. Although most fruit growers switched to chemicals, a few hung onto their ants. Those who abandoned ants in favour of chemicals quickly became disillusioned. As costs soared and pests began to develop resistance to the chemicals, growers began to revive the old ant patrols.
They had good reason to have faith in their insect workforce. Research in the early 1960s showed that as long as there were enough ants in the trees, they did an excellent job of dispatching some pests— mainly the larger insects—and had modest success against others. Trees with yellow ants produced almost 20 per cent more healthy leaves than those without. More recent trials have shown that these trees yield just as big a crop as those protected by expensive chemical sprays.
H. One apparent drawback of using ants—and one of the main reasons for the early skepticism by Western scientists was that citrus ants do nothing to control mealy bugs, waxy-coated scale insects which can do considerable damage to fruit frees. In fact, the ants protect mealy bugs in exchange for the sweet honeydew they secrete. The orange growers always denied this was a problem but Western scientists thought they knew better. Research in the 1980s suggests that the growers were right all along.
Where mealy bugs proliferate under the ants’ protection they are usually heavily parasitized and this limits the harm they can do. Orange growers who rely on carnivorous ants rather than poisonous chemicals maintain a better balance of species in their orchards. While the ants deal with the bigger insect pests, other predatory species keep down the numbers of smaller pests such as scale insects and aphids. In the long run, ants do a lot less damage than chemicals-and they’re certainly more effective than excommunication.
Questions
Questions 14-18
Use the information in the passage to match the year (listed A-G) with correct description below. Write the appropriate letters A-G in boxes 14-18 on your answer sheet.
NB you may use any letter more than once
A 1888
B 1476
C 1915
D 1700
E 1130
F AD
G 1950
14 First record of ant against pests written.
15 WS studied ant intervention method in China.
16 First case of orange crops rescued by insect in western world.
17 Chinese farmers start to choose chemical method.
18 A book wrote mentioned ways to trap ants.
Questions 19-26
Do the following statements agree with the information given in Reading Passage?
In boxes 19-26 on your answer sheet, write
TRUE if the statement is true
FALSE if the statement is false
NOT GIVEN if the information is not given in the passage
19 China has the most citrus pests counted in types in the world.
20 Swingle came to China in order to search an insect for the US government.
21 Western people were impressed by Swingle’s theory of pest prevention.
22 Chinese farmers realised that price of pesticides became expensive.
23 Some Chinese farmers start to abandon the use of pesticide.
24 Trees without ants had grown more unhealthy leaves than those with.
25 Yield of fields using ants is larger a crop than that using chemical pesticides.
26 Chinese orange farmers proposed that ant protection doesn’t work out of China.
Answers
Below are the answers, key words, synonyms and full explanations for the IELTS Reading passage Chinese Yellow Citrus Ant for Biological Control (Passage 2, Questions 14–26).
Questions 14–18: Matching Years (A 1888, B 1476, C 1915, D 1700, E 1130, F 304 AD, G 1950)
14. First record of ant against pests written.
Answer: F (304 AD)
Key words: The earliest report of citrus ants at work among the orange trees appears in a book … written by His Han in AD 304
Synonyms: first written record of ants against pests = the earliest report of citrus ants, in a book of AD 304 = “The earliest report of citrus ants at work among the orange trees appears in a book on tropical and subtropical botany written by His Han in AD 304”
Explanation: The earliest written record of the citrus ant dates to His Han’s book of AD 304 → F.
15. WS studied the ant intervention method in China.
Answer: C (1915)
Key words: in 1915 Walter Swingle … was … sent to China … Swingle spent some time studying the citrus orchards around Guangzhou
Synonyms: WS studied the ant method in China = Walter Swingle studied the citrus orchards in China in 1915 = “in 1915 Walter Swingle, a plant physiologist … sent to China … came across the story of the cultivated ant”
Explanation: Walter Swingle (WS) studied the Chinese ant method in 1915 → C.
16. First case of orange crops rescued by an insect in the western world.
Answer: A (1888)
Key words: The first breakthrough had come in 1888, when the infant orange industry in California had been saved from extinction by the Australian vedalia beetle
Synonyms: first western case of crops saved by an insect = California’s orange industry saved by the vedalia beetle in 1888 = “The first breakthrough had come in 1888, when the infant orange industry in California had been saved … by the Australian vedalia beetle”
Explanation: The West’s first biocontrol success was California in 1888 → A.
17. Chinese farmers start to choose a chemical method.
Answer: G (1950)
Key words: the long tradition of ants in the Chinese orchards only began to waver in the 1950s and 1960s with the introduction of powerful … chemical insecticides
Synonyms: Chinese farmers turn to chemicals = the ant tradition wavered in the 1950s with chemical insecticides = “the long tradition of ants … only began to waver in the 1950s and 1960s with the introduction of powerful organic … insecticides”
Explanation: Chinese growers began switching to chemicals in the 1950s → G.
18. A book wrote mentioned ways to trap ants.
Answer: E (1130)
Key words: “Fruit growing families buy these ants … they trap them by filling hogs’ or sheep’s bladders with fat …” wrote Chuang Chi-Yu in 1130
Synonyms: a book describing how to trap ants = Chuang Chi-Yu’s 1130 account of baiting bladders with fat = “From the 10th century, country people began to trap ants in artificial nests baited with fat … wrote Chuang Chi-Yu in 1130”
Explanation: Chuang Chi-Yu’s 1130 book describes trapping ants with fat-baited bladders → E.
Questions 19–26: True / False / Not Given
19. China has the most citrus pests, counted in types, in the world.
Answer: TRUE
Key words: As the ancestral home of oranges, lemons and pomelos, China also has the greatest diversity of citrus pests
Synonyms: most citrus pests by type = the greatest diversity of citrus pests = “China also has the greatest diversity of citrus pests”
Explanation: China has the greatest diversity (most types) of citrus pests → TRUE.
20. Swingle came to China in order to search for an insect for the US government.
Answer: FALSE
Key words: sent to China in search of varieties of orange that were resistant to the disease
Synonyms: came to search for an insect (contradicted) = he was sent to find disease-resistant orange varieties = “Walter Swingle … was … sent to China in search of varieties of orange that were resistant to the disease”
Explanation: Swingle went to find disease-resistant orange varieties, not an insect → FALSE.
21. Western people were impressed by Swingle’s theory of pest prevention.
Answer: FALSE
Key words: Yet despite this report, many Western biologists were skeptical
Synonyms: impressed (contradicted) = Western biologists were skeptical = “Swingle was just as impressed. Yet despite this report, many Western biologists were skeptical”
Explanation: Western biologists were skeptical, not impressed → FALSE.
22. Chinese farmers realised that the price of pesticides became expensive.
Answer: TRUE
Key words: As costs soared and pests began to develop resistance to the chemicals, growers began to revive the old ant patrols
Synonyms: pesticides became expensive = the costs of chemicals soared = “As costs soared and pests began to develop resistance to the chemicals, growers began to revive the old ant patrols”
Explanation: Growers found chemical costs soared, i.e. pesticides became expensive → TRUE.
23. Some Chinese farmers start to abandon the use of pesticide.
Answer: TRUE
Key words: Although most fruit growers switched to chemicals, a few hung onto their ants … growers began to revive the old ant patrols
Synonyms: some abandon pesticides = a few kept their ants and growers revived ant patrols = “a few hung onto their ants … growers began to revive the old ant patrols”
Explanation: Some growers kept or returned to ants, giving up chemicals → TRUE.
24. Trees without ants had more unhealthy fallen leaves than those with.
Answer: TRUE
Key words: Trees with yellow ants produced almost 20 per cent more healthy leaves than those without
Synonyms: trees without ants had more unhealthy leaves = trees with ants had 20% more healthy leaves than those without = “Trees with yellow ants produced almost 20 per cent more healthy leaves than those without”
Explanation: Trees without ants had fewer healthy (more unhealthy) leaves → TRUE.
25. Yield of fields using ants is a larger crop than that using chemical pesticides.
Answer: FALSE
Key words: these trees yield just as big a crop as those protected by expensive chemical sprays
Synonyms: larger crop (contradicted) = just as big a crop, not larger = “these trees yield just as big a crop as those protected by expensive chemical sprays”
Explanation: Ant-protected trees yield just as big a crop, not a larger one → FALSE.
26. Chinese orange farmers proposed that ant protection doesn’t work outside China.
Answer: NOT GIVEN
Key words: the idea of using one insect to destroy another was new and highly controversial (in the West)
Synonyms: farmers said ants don’t work abroad = no such claim by Chinese farmers is made = “In the West, the idea of using one insect to destroy another was new and highly controversial”
Explanation: The passage never says Chinese farmers claimed the method fails outside China → NOT GIVEN.
Answer Key (Quick Reference)
| Q | Answer | Q | Answer |
|---|---|---|---|
| 14 | F (304 AD) | 21 | FALSE |
| 15 | C (1915) | 22 | TRUE |
| 16 | A (1888) | 23 | TRUE |
| 17 | G (1950) | 24 | TRUE |
| 18 | E (1130) | 25 | FALSE |
| 19 | TRUE | 26 | NOT GIVEN |
| 20 | FALSE |
