Biological Control Of Pests — IELTS Reading Answers

The use of pesticides has contributed to

1. Aa change in the way ecologies are classified by agroecologists.
2. Ban imbalance in many ecologies around the world.correct
3. Cthe prevention of ecological disasters in some parts of the world.
4. Dan increase in the range of ecologies which can be usefully farmed.

“Apart from engendering widespread ecological disorders, pesticides have contributed to the emergence of a new breed of chemical-resistant, highly lethal superbugs”

'Widespread ecological disorders' is paraphrased by option B's imbalance in many ecologies; the superbugs detail is an additional harm, not the answer.

The Food and Agriculture Organisation has counted more than 300 agricultural pests which

1. Aare no longer responding to most pesticides in use.correct
2. Bcan be easily controlled through the use of pesticides.
3. Ccontinue to spread disease in a wide range of crops.
4. Dmay be used as part of bio-control’s replacement of pesticides.

“According to a recent study by the Food and Agriculture Organisation (FAO), more than 300 species of agricultural pests have developed resistance to a wide range of potent chemicals”

Option A restates 'developed resistance to a wide range of potent chemicals' — the pests no longer respond to most pesticides in use.

Cotton farmers in Central America began to use pesticides

1. Abecause of an intensive government advertising campaign.
2. Bin response to the appearance of new varieties of pest.
3. Cas a result of changes in the seasons and the climate.
4. Dto ensure more cotton was harvested from each crop.correct

“In the early 1940s, basking in the glory of chemical-based intensive agriculture, the farmers avidly took to pesticides as a sure measure to boost crop yield”

'A sure measure to boost crop yield' matches option D: they used pesticides to get more cotton from each crop, not because of advertising or new pests.

By the mid-1960s, cotton farmers in Central America found that pesticides

1. Awere wiping out 50% of the pests plaguing the crops.
2. Bwere destroying 50% of the crops they were meant to protect.
3. Cwere causing a 50% increase in the number of new pests reported.
4. Dwere costing 50% of the total amount they spent on their crops.correct

“By the mid-1960s, the situation took an alarming turn with the outbreak of four more new pests, necessitating pesticide spraying to such an extent that 50% of the financial outlay on cotton production was accounted for by pesticides”

'50% of the financial outlay on cotton production' means pesticides absorbed half their total spending, exactly option D; the other options misread the percentage.

Disease-spreading pests respond more quickly to pesticides than agricultural pests do.

“According to a recent study by the Food and Agriculture Organisation (FAO), more than 300 species of agricultural pests have developed resistance to a wide range of potent chemicals.”

The text gives numbers for both groups but never compares how quickly each developed resistance, so a claim about responding 'more quickly' is unsupported.

A number of pests are now born with an innate immunity to some pesticides.

“Because of their tremendous breeding potential and genetic diversity, many pests are known to withstand synthetic chemicals and bear offspring with a built-in resistance to pesticides”

'Bear offspring with a built-in resistance' means the young are born already immune, which is precisely innate immunity. YES.

Biological control entails using synthetic chemicals to try and change the genetic make-up of the pests’ offspring.

“In the face of the escalating perils from indiscriminate applications of pesticides, a more effective and ecologically sound strategy of biological control, involving the selective use of natural enemies of the pest population, is fast gaining popularity – though, as yet, it is a new field with limited potential”

Biological control means 'selective use of natural enemies', not synthetic chemicals or altering pest genes, so the definition is contradicted.

Bio-control is free from danger under certain circumstances.

“When handled by experts, bio-control is safe, non-polluting and self-dispersing”

'When handled by experts, bio-control is safe' confirms it is free from danger in that circumstance. YES.

Disapene scale insects feed on

“CIBC is also perfecting the technique for breeding parasites that prey on ‘diaspine scale’ insects – notorious defoliants of fruit trees in the US and India”

'Diaspine scale' insects are 'notorious defoliants of fruit trees', so ending D, fruit trees, is what they feed on and destroy.

Neodumetia sangawani ate

“A natural predator indigenous to India, Neodumetia sangawani, was found useful in controlling the Rhodes grass-scale insect that was devouring forage grass in many parts of the US”

Neodumetia sangawani controlled the Rhodes grass-scale insect, so it ate grass-scale insects (H), not the forage grass itself.

Leaf-mining hispides blighted

“In the late 1960s, when Sri Lanka’s flourishing coconut groves were plagued by leaf-mining hispides, a larval parasite imported from Singapore brought the pest under control”

The hispides 'plagued' Sri Lanka's coconut groves, so they blighted coconut trees — ending C.

An Argentinian weevil may be successful in wiping out

“Similarly the Hyderabad-based Regional Research Laboratory (RRL), supported by CIBC, is now trying out an Argentinian weevil for the eradication of water hyacinth, another dangerous weed, which has become a nuisance in many parts of the world”

The weevil is being tried 'for the eradication of water hyacinth', so ending E, water hyacinth, completes the sentence.

Salvinia molesta plagues

“About 30,000 hectares of rice fields in Kerala are infested by this weed”

This weed infests '30,000 hectares of rice fields', so Salvinia molesta plagues rice fields, ending B.