Top 2 Ways for Managing Harmful Insects | Zoology

The following points highlight the top two ways for managing harmful insects. The ways are: 1. Chemical Management 2. Biological Management.

Way # 1. Chemical Management:

Chemicals used to kill insects are known as insecticides. Injurious insects are killed by certain chemicals, viz. hydrocyanic acid, sul­phur dioxide, arsenic, etc.

But there are other chemicals which are more specially detri­mental to the insects, namely pyrethrum and a number of chlorinated hydrocarbons, such as Dichloro Diphenyl Trichloroethane (D.D.T.), benzene hydrochloride (B.H.C). Or- ganophosphates are extensively used as sys­tematic poison.

The majority of these insec­ticides are believed to act primarily on the nervous system of insects and paralyze them, some very rapidly. The insecticides are ab­sorbed either through the cuticle or the stom­ach.

Modes of Use of Insecticides:

Insecticides are used in the form of dusts, solutions, emulsions, water suspensions and fumigants; or these may be mixed up with the food and used as bait.

a. Dusting:

Applied to protect the health of man or animals against insects.

b. Residual sprays:

Chlorinated hydro­carbons can be mixed up—usually with kero­sene oil—or some other suitable medium and sprayed.

c. Space sprays:

These are effective in small indoor disinfections. They may be sprayed in the form of fogs, mists, smokes, etc.

d. Water treatment:

Applied to kill aquatic larvae of mosquitoes. Paris green dust is effective only in the case of Anopheles lar­vae.

e. Skin application:

Application of insec­ticides, particularly D.D.T., is effective in case of animals, since it is not absorbed through the skin.

f. Fumigation:

Hydro carbonic acid gas is a powerful fumigant and is extensively used, but it is very toxic to all forms of life.

Repellants:

These are chemicals which may be ap­plied to the skin or clothing to keep off insects from biting. Indalone, is particularly effective against biting flies and some mos­quitoes.

Way # 2. Biological Management:

Insects may be controlled by other in­sects; some insects devour the eggs and adults of others.

Common Insect-Borne Diseases:

a. Sucking lice:

Ectoparasite on mammals, feed on blood; two species are parasites on man. Diseases are transmitted by continua­tion of scratches in the human body; or by excreta, or by the excreta of the infected louse.

b. Mosquitoes:

(i) Anopheles:

Females are carriers of malaria parasites.

(ii) Culex:

Intermediate hosts for filaria. They are also carrier for the causative agents of dengue fever.

c. Flies:

Carrier of many pathogenic bac­teria like those of cholera and typhoid.

d. Rat flea:

Carry bacilli from diseased rat to man. The plague bacilli rapidly mul­tiply in the haemolymph of the flea and when the flea bites a man, the bacilli are released in the blood of the victim.