272
C. R. Krishna Murti and T. S. S. Dikshith
studied (Dewan et al., 1969). Degradation of malathion and its formulations
WOP, granules, E.C., and dusts was faster under higher temperatures, low
humidity, and bright sunshine (Hameed and Rattan Lal, 1971). In winter, E.C.
formulation took 12 days, WOP 14 days, and dusts 5 days for residues to reach
levels below the tolerance limit of 8 ppm. Malathion applied (0.054>.15%) on
paddies degraded rapidly, reaching undetectable levels within 3 days (Srivastava
et al., 1975). The half-life ranged from 1.3 to 2.1 days. The level was below
the EPA tolerance limit of 8 ppm in 48 hr after a single spray. However, the
half-life of malathion on green grass is 2.46 months (Murthy and Srivastava,
1977).
Malathion spray (0.5 and 1.0%) left an initial residue of 11.67-16.72 ppm
on small fruits, 3.2-10.39 ppm on medium-sized fruits, and 2.58-4.68 ppm on
normal-sized fruits of okra (A. esculantus). However, the level of residue dropped
to below 3 ppm after 48 hr. Also, washing of the fruits removed more than 80%
of the malathion residue (Jat and Srivastava, 1973). Folin application of dicrotophos (0.05%) left a residue of 7.5 ppm on Bengal gram (Cicer arietinum) pods
at harvest. A spray of endosulfan (0.07%) at the time of pod formation in Bengal
gram left a high residue of the insecticide both on the whole plant and in the
grain even 25 days after treatment, suggesting that care be taken during the spray
schedule and in the pattern of use (Pandey et al., 1977).
In cow pea pods treated with monocrotophos (0.75-1.25 kg A.I.lha) the
half-life of the pesticide ranged between 2.7 and 3.1 days (Awasthi et al.,
1977a). Monocrotophos applied to soil is quickly degraded and no residue was
seen in sugar cane juice (Awasthi et al., 1977b). Soybeans sprayed with carbaryl
(0.1 % showed no detectable levels of residues in grains, straw, and husks at
harvest (Awasthi et al., 1979).
Parathion dissipated and degraded rapidly in cabbage (Singh et al., 1971).
Residues were reduced to less than 1.0 ppm in 1 day and were undetectable after
21 days. The half-life of parathion on cabbage varied from 1.67 to 1.81 days,
and no residue could be detected in random samples of cabbage collected from
the market. Phorate applied to puddled paddy soils degraded completely within
30 days (Rajukkannu et al., 1977).
When Bengal gram was sprayed with 0.044>.05% solutions of tetrachlorovinphos, carbophenothion, and trichlorfon, residues were found to be excessive
in the grains at harvest. Examination of the harvest grains showed 6.0 ppm of
tetrachlorvinphos, 3.5 ppm of carbophenothion, and 13.5 ppm of trichlorofon
(Pandley et al., 1977).
10.5.2. Organochlorine Insecticides
Residue levels of DDT and BHC on spinach (Spinacia olearacea) leaves
were estimated after spraying them with 0.1 % solutions. While the residue levels
C. R. Krishna Murti and T. S. S. Dikshith
studied (Dewan et al., 1969). Degradation of malathion and its formulations
WOP, granules, E.C., and dusts was faster under higher temperatures, low
humidity, and bright sunshine (Hameed and Rattan Lal, 1971). In winter, E.C.
formulation took 12 days, WOP 14 days, and dusts 5 days for residues to reach
levels below the tolerance limit of 8 ppm. Malathion applied (0.054>.15%) on
paddies degraded rapidly, reaching undetectable levels within 3 days (Srivastava
et al., 1975). The half-life ranged from 1.3 to 2.1 days. The level was below
the EPA tolerance limit of 8 ppm in 48 hr after a single spray. However, the
half-life of malathion on green grass is 2.46 months (Murthy and Srivastava,
1977).
Malathion spray (0.5 and 1.0%) left an initial residue of 11.67-16.72 ppm
on small fruits, 3.2-10.39 ppm on medium-sized fruits, and 2.58-4.68 ppm on
normal-sized fruits of okra (A. esculantus). However, the level of residue dropped
to below 3 ppm after 48 hr. Also, washing of the fruits removed more than 80%
of the malathion residue (Jat and Srivastava, 1973). Folin application of dicrotophos (0.05%) left a residue of 7.5 ppm on Bengal gram (Cicer arietinum) pods
at harvest. A spray of endosulfan (0.07%) at the time of pod formation in Bengal
gram left a high residue of the insecticide both on the whole plant and in the
grain even 25 days after treatment, suggesting that care be taken during the spray
schedule and in the pattern of use (Pandey et al., 1977).
In cow pea pods treated with monocrotophos (0.75-1.25 kg A.I.lha) the
half-life of the pesticide ranged between 2.7 and 3.1 days (Awasthi et al.,
1977a). Monocrotophos applied to soil is quickly degraded and no residue was
seen in sugar cane juice (Awasthi et al., 1977b). Soybeans sprayed with carbaryl
(0.1 % showed no detectable levels of residues in grains, straw, and husks at
harvest (Awasthi et al., 1979).
Parathion dissipated and degraded rapidly in cabbage (Singh et al., 1971).
Residues were reduced to less than 1.0 ppm in 1 day and were undetectable after
21 days. The half-life of parathion on cabbage varied from 1.67 to 1.81 days,
and no residue could be detected in random samples of cabbage collected from
the market. Phorate applied to puddled paddy soils degraded completely within
30 days (Rajukkannu et al., 1977).
When Bengal gram was sprayed with 0.044>.05% solutions of tetrachlorovinphos, carbophenothion, and trichlorfon, residues were found to be excessive
in the grains at harvest. Examination of the harvest grains showed 6.0 ppm of
tetrachlorvinphos, 3.5 ppm of carbophenothion, and 13.5 ppm of trichlorofon
(Pandley et al., 1977).
10.5.2. Organochlorine Insecticides
Residue levels of DDT and BHC on spinach (Spinacia olearacea) leaves
were estimated after spraying them with 0.1 % solutions. While the residue levels