Text 18 pest control

Methods

May-beetles especially the larvae which attack the roots of young pine-trees cause great damage to forests. Special care must be taken to protect the forest belts.

The measures taken to control insect pests are divided into several groups: chemical, physical, biological and cultural.

Chemical control is carried out by means of various insecticides. How successful these measures are depends on our knowledge of the life and habits of the pests, especially their eating habits.

Leaf-eating pests (locust, butterfly caterpillars, beetles) can be destroyed with "stomach poisons", sprayed or dusted onto the leaves of the plants they attack. The pests take in the insecticides which get into their digestive tracts.

Insects which suck the sap of plants are not affected by stomach poisons but can be destroyed with contact insecticides, for instance, DDT, which is most effective against the Sen Stink Bug.

Tracheal insecticides, introduced as gases or as clouds of smoke which enter the bodies of insects through the tracheae, are effective against those that attack seeds, and are sometimes used in storehouses,

Besides destroying pests, insecticides may injure useful insects, such as Bees, Bumble-bees, Silkworm Moths (Bombyx), Ichneumon Flies, and Ladybirds. Therefore there are times when they should not be used. The use of DDT and other toxic chemicals, for instance, is banned in the vicinity of beehives and silkworm breeding farms.

A number of insecticides are harmful to man and should not be used on flowering plants or fruit.

Insecticides are spread by means of different dusting and spraying machines.

Physical methods of control include collecting of eggs, caterpillars and chrysalises by hand, shaking the insects off the plants, trapping them with grease bands, etc.

Biological control is a method of destroying pests by using their own natural enemies against them, for instance, the Trichogramma (which may be specially bred for the purpose), and the encouragement of insectivorous birds.

Cultural control consists of effective methods of cultivation, ploughing, applying fertilizer, etc., to ensure that plants are strong and healthy and able to resist the attacks of insect pests.

Sometimes changing the sowing time is effective: damage can be avoided if crops are sown after the insects have appeared, or early so that they are far enough advanced to resist attack.

Tasks

1. Write down whether the following statements are true or false. Give extensive answers.

1. May-beetles attack the roots of young pine-trees.

2. Chemical control is carried out by different machines.

3. DDT is most effective against may-beetles and butterflies.

4. Pests and insecticides are useful to man and should be used on flowering plants and fruit.

5. Cultural control includes collecting of eggs and caterpillars by hand, shaking the insects off the plants.

2. Complete the sentences using the text and translate them into Russian.

1. Insecticides are spread by means … .

2. Sometimes changing the sowing time … .

3. Special care must be taken … .

4. The use od DDT and other toxic … .

5. The pests take in the insecticides … .

6. Leaf-eating pests … .

7. Chemical control is carried out by means … .