Application of Biodegradable Pesticides in India
267
as carbaryl, monocrotophos, paraquat, and bavistin are expected to be produced
indigenously.
The Indian Council of Scientific and Industrial Research has also supported
R&D activities in national laboratories for the development of technology. As
a result, process packages for the manufacture of several known pesticides such
as endosulfan, MBC, nitrofen, atrazine, simazine, dalapon, monocrotophos,
diazinon, quinalphos, phosphamidon, DDVP, methoxychlor, and carboxin have
been developed. Works on the following pesticides are at various stages of
development: carbaryl, metasystox, methyl parathion, phosalone, thiometon,
carbofuran, propanil, divron, paraquat, and diazinon.
10.3. BIODEGRADA TlON OF PESTICIDES BY
MICROORGANISMS
Pesticides are acted upon by a variety of interrelated physical and chemical
factors and microbial organisms. Physicochemical reactions could lead to incomplete degradation with the formation of products that continue to persist.
More complete transformation of pesticides is mediated essentially by microorganisms, the role of some of which is now well established in soil and water.
That many pesticides are biotransformed by microorganisms is now well recognized (Alexander, 1965; Kearney and Kaufman, 1969; Kaufman and Kearney,
1970; Kandaswamy et at., 1977; Sheela and Vasantharajan, 1978a,b; Griffiths
and Walker, 1970; Patil et at., 1972; Sethunathan, 1973; Balasubramanya and
Patil, 1976; Chahal et at., 1977). Factors such as moisture, temperature, organic
matter, fertilizers, and surfactants can affect the degradation of pesticides in soil.
In general, moisture, high temperature, and high organic matter in soil enhance
the rate of degradation. Fertilizers and surfactants, on the other hand, could
suppress the rate of degradation significantly, the effect being modulated by the
action of soil microftora (Anonymous, 1978b).
A major quantity of orthane, ingested by the body, is excreted within 24
hr. Buildup in soil does not occur, nor does it accumulate in the natural food
chain (Anonymous, 1973). It kills a wide range of pests, especially those which
have developed resistance to chlorinated hydrocarbons. However, it is not as
effective as chlorinated hydrocarbons against soil pests. Methomyl, a carbamate
insecticide, has been known to undergo biodegradation very rapidly in soil,
presumably mediated by soil microorganisms (Harvey and Pease, 1973). Methomyl has no residual effect in tobacco, cotton, and cabbage, since it has a halflife of only 3-6 days (Harvey and Reiser, 1973).
Unlike organochloride insecticides, the organophosphorus compounds are
readily degraded on the surface of plants, inside their tissues, and in soil and
water and hence may pose less serious problems of environmental pollution than
those caused by organochlorine pesticides. The fate of parathion in certain rice-
267
as carbaryl, monocrotophos, paraquat, and bavistin are expected to be produced
indigenously.
The Indian Council of Scientific and Industrial Research has also supported
R&D activities in national laboratories for the development of technology. As
a result, process packages for the manufacture of several known pesticides such
as endosulfan, MBC, nitrofen, atrazine, simazine, dalapon, monocrotophos,
diazinon, quinalphos, phosphamidon, DDVP, methoxychlor, and carboxin have
been developed. Works on the following pesticides are at various stages of
development: carbaryl, metasystox, methyl parathion, phosalone, thiometon,
carbofuran, propanil, divron, paraquat, and diazinon.
10.3. BIODEGRADA TlON OF PESTICIDES BY
MICROORGANISMS
Pesticides are acted upon by a variety of interrelated physical and chemical
factors and microbial organisms. Physicochemical reactions could lead to incomplete degradation with the formation of products that continue to persist.
More complete transformation of pesticides is mediated essentially by microorganisms, the role of some of which is now well established in soil and water.
That many pesticides are biotransformed by microorganisms is now well recognized (Alexander, 1965; Kearney and Kaufman, 1969; Kaufman and Kearney,
1970; Kandaswamy et at., 1977; Sheela and Vasantharajan, 1978a,b; Griffiths
and Walker, 1970; Patil et at., 1972; Sethunathan, 1973; Balasubramanya and
Patil, 1976; Chahal et at., 1977). Factors such as moisture, temperature, organic
matter, fertilizers, and surfactants can affect the degradation of pesticides in soil.
In general, moisture, high temperature, and high organic matter in soil enhance
the rate of degradation. Fertilizers and surfactants, on the other hand, could
suppress the rate of degradation significantly, the effect being modulated by the
action of soil microftora (Anonymous, 1978b).
A major quantity of orthane, ingested by the body, is excreted within 24
hr. Buildup in soil does not occur, nor does it accumulate in the natural food
chain (Anonymous, 1973). It kills a wide range of pests, especially those which
have developed resistance to chlorinated hydrocarbons. However, it is not as
effective as chlorinated hydrocarbons against soil pests. Methomyl, a carbamate
insecticide, has been known to undergo biodegradation very rapidly in soil,
presumably mediated by soil microorganisms (Harvey and Pease, 1973). Methomyl has no residual effect in tobacco, cotton, and cabbage, since it has a halflife of only 3-6 days (Harvey and Reiser, 1973).
Unlike organochloride insecticides, the organophosphorus compounds are
readily degraded on the surface of plants, inside their tissues, and in soil and
water and hence may pose less serious problems of environmental pollution than
those caused by organochlorine pesticides. The fate of parathion in certain rice-