Insect Pests of Vegetable, Tuber and Spice Crops

Pestcides

Pesticides

Pesticides:

• Pesticides are the poisonous substances intentionally used on crops to control, destroy, repel, prevent and mitigate the pests.
• Dissipated with time but at the same time they persist accumulate and contaminate environment.
• Accumulate in the body.
• Transferred from one trophic level to another with magnification at each level (bio-magnification).

Environmental impacts of synthetic pesticides:
1) Insecticide resistance:

• Development of an ability to tolerate a dose of an insecticide which would prove lethal to the majority of the individuals in a population of the same species.
• This ability results due to genetic change in a pest population in response to toxicants
• First documented case of insecticide resistance appeared in 1914 when Sanjose scale was reported resistant against hydrogen cyanide.
• Over 600 species have developed resistance against one or the other insecticide.

2) Insect resurgence:

• Abnormal increase in pest population or damage following insecticide application often far exceeding the EIL.

3) Secondary pest outbreaks:

• Due to indiscriminate use of pesticides natural enemies suffer badly
• In the absence of natural enemies the minor pests multiply rapidly and attain the status of major pests.

4) Toxicity to non-target organisms:

• Most of the pesticides are biocides basically meant for killing.
• Without discrimination they kill every organism
• Common categories of non target organisms which suffer are

• Natural enemies
• Pollinators
• Soil organisms
• Fishes

5) Human toxicity and health hazards:
Acute toxicity:

• Toxicity resulted due to single dose of a toxicant.

Chronic toxicity

• Toxicity resulted due to the repeated exposure of an organism to sub lethal doses of a toxicant.
• Toxicant gets accumulated (bio-accumulation) in the body which ultimately results in ill effects in the body.
• Ill effects can be carcinogenic, teratogenic, mutagenic, failure of vital body organs, infertility, etc.
• 3 million acute poisoning cases occur world wide every year out of which 2 millions are of suicide and rest are of occupational or accidental poisoning cases.
• 108 people died due to parathion poisoning in Kerala in 1953.
• Bhopal gas tragedy at Union Carbide Plant in Bhopal during 1984 where the vapours of methyl isocyanate, an intermediate for the manufacturing of carbaryl were leaked from the plant.
• In this tragedy at least 5000 people were killed, 50,000 were disabled permanently and in total 2, 00,000 people were affected.
• According to a report by Natural Resource defense council (NRDC) of USA one out of every 3400 children between 1 and 5 years of age could one day get cancer due to pesticides.
• In India cases of blindness, cancer, diseases of liver and nervous system from pesticides have been reported from cotton growing areas of Andhra Pradesh and Maharastra.
• Symptoms like anxiety, sleep disturbance, depression and severe headache have been reported in people regularly involved in spraying of DDT and malathion.