| 
There
is no getting away from insects, is there? They are in the soil
beneath our feet, in the air above our head, on and inside the bodies
of the plants and animals around us, as well as on and inside us!
There are well over one million different known species of insects
in the world. Some experts estimate that the unknown species may
add up to as many as 10 million.
All these species are divided up into about 32 orders, of which,
the largest is the Beetles, or Coleoptera. With clan of 125 different
families and around 500,000 species insects are an incredibly diverse
group of animals. In fact, one in every four animal species on this
planet is a beetle!
Of all the animal species on earth, an astounding 97 per cent are
estimated to be invertebrates (with no backbone). Ants form 10 per
cent of the animal biomass of the world. Another 10 per cent is
composed of termites. In other words, these insects make up an incredible
20 per cent of the total animal biomass of this planet.
Exploring the world of insects and their closest relatives — the
arthropods — who make up 80 per cent of the species in the animal
kingdom, can actually be a fascinating experience. Want to try?
Begin by identifying the distinctive characteristics of insects,
arachnids, centipedes, millipedes and crustaceans.
The abundance of insects in nature clearly establishes one fact:
the critters, big and small, play a major role in sustaining our
ecosystems.
Fight
for food
Why
are human beings and insects always in conflict? One obvious reason
is the sense of disgust that most of the creepy-crawlies seem to
stir up. And some insects can actually cause physical harm, so self-defense
comes into play, naturally.
But, the most apparent area of conflict is appropriation of food.
Insects and human beings put together are the two largest consumers
of biomass (both plant and animal ) on our planet. As the human
population grows, we need more food and since land is becoming a
scarce commodity we need a larger share of the produce. The most
effective way to achieve that is by eliminating the second largest
consumer of biomass on Earth. So, the battle between insects and
us is fought every year at global scale on farmlands and in human
settlements.
Poison
them
What
do we do to get rid of insects? We poison them. The pesticide industry
is one of the largest industries in the world. We began with the
use of broad spectrum (general) pesticides and now we manufacture
organism specific hormone-based pesticides. We have managed to get
rid of insects from our habitat to a very large extent. Without
these potent chemical pesticides we would have had ten times the
number of insects we now find at our homes.
A better understanding of how insects grow and develop has contributed
greatly to their management. For example, knowledge of the hormonal
control of insect metamorphosis led to the development of a new
class of insecticides called insect growth regulators (IGR). Based
on information about growth rates relative to temperature, computer
models are used to predict when insects would be most abundant during
the growing season and, consequently, when crops are most at risk.
An insect’s environment may be described by physical factors including
temperature, wind, humidity, light, and biological factors such
as other members of the species, food sources, natural enemies,
and competitors (organisms using the same space or food source).
An understanding of these factors and how they relate to insect
diversity, activity (timing of insect appearance or phenology),
and abundance is critical for successful pest management.
Enter the Goliath: pesticide industry
These
are chemicals used to destroy insects. Insecticides include ovicides
and larvicides that kill eggs and larva. They are used in agriculture,
in medicines, in industries and at home. The use of insecticides
is believed to be one of the major factors behind the increase in
agricultural productivity in the 20th century.
India is a voracious consumer of pesticides. The total demand for
insecticides here is over 1,00,000 metric tonnes (MT) for agricultural
and 50,000 MT for public health purposes. Consumption of insecticide
in agriculture has grown by more than 100 per cent from 1971 to
1994-95. For instance, insecticide consumption in India, which was
to the tune of 22,013 tonnes has increased to 51,755 tonnes by 1994-95
(www.indiastat.com).
But in recent past, a change has been observed in the trend of pesticides
consumption. As a result of adoption of bio intensive Integrated
Pest Management Programme in various crops, the consumption of chemical
pesticide has come down from 66.36 thousand MT during 1994-95 to
43.59 thousand MT during 2001-02.
But reduction in the volume of pesticides produce is really not
significant, because the products manufactured now are more potent,
and more toxic.
Are
we an entomophobic nation?
Interestingly,
consumption pattern of pesticides in India is very different from
the rest of the world. In India, insecticides account for 76 per
cent of the total domestic market while herbicides and fungicides
have a significantly higher share in the global market. We seem
to kill insects with extra fervour! Now let’s take a look at what
these poisons are made of. In India, the most commonly used pesticides
are monocrotophos, Chlorpyrifos, Quinalphos, Endosulfan, Cypermethrin
and Fenvalerate. |
