4
Microbial Degradation of Pesticides
in Tropical Soils
N. Sethunathan, T. K. Adhya, and K. Raghu
4.1. INTRODUCTION
Hot and humid conditions of the tropical and subtropical environments, as exist
in most developing countries, favor the buildup of a myriad of insect pests and
disease pathogens harmful to man and his agriculturally important crops. Furthermore, in recent years, intensive and extensive cultivation of new high-yielding crop varieties with high nitrogen input in several tropical countries has led
to serious outbreaks of certain insect pests that were previously considered minor
pests, such as brown planthoppers (Nilaparvata lugens) in rice (Kulshreshtha et
al., 1974). Consequently, there has been a steady increase in the use of pesticides
in most tropical countries in recent years. Pesticide use in most developing
countries is still very low, with an input of 330 g/ha in India as compared to
1490 g/ha in a developed country such as Japan (Anonymous, 1979a). However,
there are localized areas of heavy pesticide use, such as in cotton, tea, and cocoa
and in irrigated rice culture, raising problems of environmental contamination.
In developed countries, herbicides constitute a major portion of all pesticides
used. But, for most tropical countries, insecticides are the most important, accounting for, as in India (Anonymous, 1979a), more than 65% of all pesticides
used.
In recent years, the use of certain chlorinated hydrocarbon pesticides has
been banned in almost all developed countries because of concern over their
N. Sethunathan and T. K. Adhya • Laboratory of Soil Microbiology, Central Rice Research
Institute, Cuttack 753006, India.
K. Raghu • Biology and Agriculture Division, Bbabba Atomic
Research Centre, Bombay 400085, India.
91
Microbial Degradation of Pesticides
in Tropical Soils
N. Sethunathan, T. K. Adhya, and K. Raghu
4.1. INTRODUCTION
Hot and humid conditions of the tropical and subtropical environments, as exist
in most developing countries, favor the buildup of a myriad of insect pests and
disease pathogens harmful to man and his agriculturally important crops. Furthermore, in recent years, intensive and extensive cultivation of new high-yielding crop varieties with high nitrogen input in several tropical countries has led
to serious outbreaks of certain insect pests that were previously considered minor
pests, such as brown planthoppers (Nilaparvata lugens) in rice (Kulshreshtha et
al., 1974). Consequently, there has been a steady increase in the use of pesticides
in most tropical countries in recent years. Pesticide use in most developing
countries is still very low, with an input of 330 g/ha in India as compared to
1490 g/ha in a developed country such as Japan (Anonymous, 1979a). However,
there are localized areas of heavy pesticide use, such as in cotton, tea, and cocoa
and in irrigated rice culture, raising problems of environmental contamination.
In developed countries, herbicides constitute a major portion of all pesticides
used. But, for most tropical countries, insecticides are the most important, accounting for, as in India (Anonymous, 1979a), more than 65% of all pesticides
used.
In recent years, the use of certain chlorinated hydrocarbon pesticides has
been banned in almost all developed countries because of concern over their
N. Sethunathan and T. K. Adhya • Laboratory of Soil Microbiology, Central Rice Research
Institute, Cuttack 753006, India.
K. Raghu • Biology and Agriculture Division, Bbabba Atomic
Research Centre, Bombay 400085, India.
91