The influence of insects on human life ‘destructive and beneficial’ can be traced back to prehistoric day and till now. A constant struggle is going on between men and insects in the pursuit of food.
This struggle will go on forever because there does not seem to be final victory on either side. To know the destructive potentialities of some insects, one should visit a countryside invaded by locusts.
Within a couple of hours of the invasion, not a blade of grass or green vegetable can be found in the area and certain scale insects can completely destroy an orchard crop. Man is himself often the victim of these insect attacks.
Agriculture is one of the important branches of Biology, which deals with the cultivation of crop plants and domestication of useful animals. Invention in agriculture by human being has brought a big revolution in the ecosystem of earth.
Of all demands of man, food is of prime importance and because of population pressure, the task of increased food production is on our natian’s priority.
In the 1970’s the so-called ‘Green Revolution’ made remarkable contribution in increasing per acre, yield of land because of high yielding varieties of wheat, rice, maize, grains and cereals.
In order to achieve our target of 250 million tonnes of food grains by 2005 A.D. insect pest control has become important part of cultivation of large number of same type of plants in vast areas provided readily available host to the pest and parasites which can also survive and attack the plants very easily.
A number of pathogens cause diseases in crop plants and domesticated animals. Such pathogens cause damage to them. This finally results in economic loss to the farmer.
In India, agriculture is the main occupation of the majority of people. The major cash crops are sugarcane, cotton, citrus, groundnut, tobacco, potato etc.
Apart from these coffee, tea, cashew nut, mango, grapes, oranges, various kinds of vegetables and flowers etc. Besides this major craps are sorghum, wheat, rice, maize, millets and many legumes are also cultivated on large scale as they have increasing market value but the most important natural enemies of agricultural crops are insects, plant diseases, weeds and weather conditions.
Gut of these, insects are most successful group of animals even in the adverse climatic conditions therefore; they are greatest competitors of man in the struggle for existence.
The insects which cause damage to crop plants are called as ‘Agricultural Pest’, In the present topic, we will study the various kinds of pest in broad sense/view.
Concept of Pest:
Pest can be defined as any organism (animal or plant} whose population increases to such an extent as to cause economic losses to crops or a nuisance and health hazard to man and his livestock or possessions will be declared as a pest.
The attack of pest to the agricultural crops causes economic loss to farmer.
According to Edwards and Heath (1964) the pest is said to be “Economic Pest” if any pest causes atleast 5% or more loss to the crops.
The amount of damage caused to a crop is called as “Economic Damage”. The lowest pest population density which causes damage is called as “Economic Injury Level”.
This varies from crop to crop, area to area and season to season. For calculating the Economic Injury Level (EIL) includes four parameters:(i) Cost of control
(ii), The market value of the crop
(iii) The yield loss attributable to a unit number of insects
(iv) The effectiveness of the control.
Stern et. al. (1959) called the density of pest population at which control measures should be started to prevent increase in pest population from reaching the economic injury level is called as ‘Economic Threshold’.