Abstract:
Studies on persistence and degradation of the synthetic pyrethroid
insecticides, permethrin and fenvalerate, were carried out under natural
environmental conditions of the Niagara Peninsula. Permethrin and
fenvalerate were treated on apple foliage atrat~s of 0.21 kg(AI)!ha
and 0.14 kg(AI)/ha, respectively. The initial cis- and trans-permethrin
spray deposits were found to be 13.5 ppm and 19.2 ppm, respectively and
38.0 ppm was observed for the fenvalerate treated sample. Twenty-three
days and 84 days after spray application, permethrin residues were 4.0 ppm
and 2.7 ppm for the cis-isomer, whereas they were 7.9 ppm and 4.7 ppm for the
trans-isomer, respectively. Residues of fenvalerate 23 days and 84 days
after spray application were 13.4 ppm and 8.0 ppm, respectively. The values
of observed half-life of cis-permethrin, trans-permethrin and fenvalerate were
found to be 42 days, 46 days and 51 days, respectively. Studies were
extended to quantitatively determine some of the major degradation
compounds of permethrin and fenvalerate, which were expected to be produced
as results of ester cleavage of the parent compounds. A permethrin
treated sample, 84 days after initial spray application, showed 0.25 and
0.8 ppm of cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic
acid (C12CA (18), respectively. These two acids
were not found as free acids, but found as conjugated compounds. The other
expected degradation compounds, 3-phenoxybenzyl alcohol (PBalc (~)),3-phenoxybenz.aldehyde (PBald (38)) and 2- (4-chlorophenyl) isovaleric acid
(CPIA (31)) were not detected by the methods employed in this study. The
results indicate that these degradation compounds were not present,
or, if they were present, their concentrations were too low to detect
by the methods used.
