Application of Biodegradable Pesticides in India
269
insecticidal defense against insect pests. In contrast to organic insecticides, the
insecticides of plant origin are relatively less toxic to man, animals, and other
plants, but are highly effective with species of insects.
Of the pesticides originating from plants, nicotine sulfate and pyrethrum
extract have wide-range use. The bulk of about 15,300 tons of pyrethrum comes
from Kenya and Tanzania. A limited amount of about 10 tons is the contribution
from India. There is a great potential for the expansion of cultivation of pyrethum
in India along the Himalayan foothills-all the way from Assam to Kashmir.
Programs are also being developed for producing synthetic pyrethrums, particularly Permethrin. This product is presently undergoing bioefficacy tests.
Various formulations of pyrethrum have been used for household sprays.
In Indian the production of different formulations of pyrethrum have gradually
increased over the years. During 1976-1977 the total production was about 2000
kiloliters; in 1977-1978 it was about 2700 kiloliters. Further, India imported
about 11,500 kg of pyrethrum during the last 2 years.
Production of nicotine sulfate from tobacco waste is steadily increasing in
India. During 1966-1967 the total production was about 23,200 kg; presently
the total quantity is about 90,000 kg.
Plants and Insecticides. Plants come in contact with insecticides either
through direct application or through soil. Direct application of sprays, dusts,
or granules to soils often leads to a low but detectable level of residues at the
time of harvest. Insecticides have been recovered from fruits, vegetables, mushrooms, grains, spices, forage crops, feeds, tobacco, and trees. Moreover, products processed from such contaminated plants also contain residues of insecticides.
Cyclodiene insecticides have been found to undergo extensive rearrangement and metabolism in living organisms and as a result of exposure to ultraviolet
light. The metabolites formed possess significant toxicity, comparable to that of
the parent compounds. Organophosphorus compounds undergo oxidative desulfuration in plants, and the reaction is mediated by the mixed-function oxidases
in the presence of NADPH and oxygen (O'Brien, 1967).
The thio ether oxidation of certain organophosphorus compounds has been
demonstrated in vivo in plants. This reaction involves the conversion of the thio
ether moiety to the respective sulfoxide and sulfone; it has been shown with
demeton, phorate, and fensulfothion.
In plants, carbaryl is metabolized to 4- and 5-hydroxy carbaryl, N-hydroxymethylcarbaryl, and I-naphthol conjugated with glucose and other sugars. In
cotton plants hydrolytic and nonhydrolytic pathways contributes almost equally
to the metabolism of carbaryl. Plants grown in carbofuran-treated soil metabolize
the insecticide to 3-hydroxycarbofuran, 2,3-dihydro-7-hydroxy-2,2-dimethyl
benzofuran, and 2,3-dihydro-3,7-dihydroxy-2,2-dimethyl benzofuran. These
products are largely stored as glycosides in plants (Knaak et al .• 1970).
269
insecticidal defense against insect pests. In contrast to organic insecticides, the
insecticides of plant origin are relatively less toxic to man, animals, and other
plants, but are highly effective with species of insects.
Of the pesticides originating from plants, nicotine sulfate and pyrethrum
extract have wide-range use. The bulk of about 15,300 tons of pyrethrum comes
from Kenya and Tanzania. A limited amount of about 10 tons is the contribution
from India. There is a great potential for the expansion of cultivation of pyrethum
in India along the Himalayan foothills-all the way from Assam to Kashmir.
Programs are also being developed for producing synthetic pyrethrums, particularly Permethrin. This product is presently undergoing bioefficacy tests.
Various formulations of pyrethrum have been used for household sprays.
In Indian the production of different formulations of pyrethrum have gradually
increased over the years. During 1976-1977 the total production was about 2000
kiloliters; in 1977-1978 it was about 2700 kiloliters. Further, India imported
about 11,500 kg of pyrethrum during the last 2 years.
Production of nicotine sulfate from tobacco waste is steadily increasing in
India. During 1966-1967 the total production was about 23,200 kg; presently
the total quantity is about 90,000 kg.
Plants and Insecticides. Plants come in contact with insecticides either
through direct application or through soil. Direct application of sprays, dusts,
or granules to soils often leads to a low but detectable level of residues at the
time of harvest. Insecticides have been recovered from fruits, vegetables, mushrooms, grains, spices, forage crops, feeds, tobacco, and trees. Moreover, products processed from such contaminated plants also contain residues of insecticides.
Cyclodiene insecticides have been found to undergo extensive rearrangement and metabolism in living organisms and as a result of exposure to ultraviolet
light. The metabolites formed possess significant toxicity, comparable to that of
the parent compounds. Organophosphorus compounds undergo oxidative desulfuration in plants, and the reaction is mediated by the mixed-function oxidases
in the presence of NADPH and oxygen (O'Brien, 1967).
The thio ether oxidation of certain organophosphorus compounds has been
demonstrated in vivo in plants. This reaction involves the conversion of the thio
ether moiety to the respective sulfoxide and sulfone; it has been shown with
demeton, phorate, and fensulfothion.
In plants, carbaryl is metabolized to 4- and 5-hydroxy carbaryl, N-hydroxymethylcarbaryl, and I-naphthol conjugated with glucose and other sugars. In
cotton plants hydrolytic and nonhydrolytic pathways contributes almost equally
to the metabolism of carbaryl. Plants grown in carbofuran-treated soil metabolize
the insecticide to 3-hydroxycarbofuran, 2,3-dihydro-7-hydroxy-2,2-dimethyl
benzofuran, and 2,3-dihydro-3,7-dihydroxy-2,2-dimethyl benzofuran. These
products are largely stored as glycosides in plants (Knaak et al .• 1970).