Dissipation kinetics of pyriproxyfen in chilli (Capsicum annum L.) and soil
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Date
2021-02
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CCSHAU, Hisar
Abstract
Pyriproxyfen, 2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy] pyridine, is a novel broad spectrum
insecticide. Dissipation of pyriproxyfen in chilli, soil and effects of washing on reduction of residues in chilli fruits
were observed under field and lab conditions. Pyriproxyfen efficacy against honey bees, its leaching potential
under continuous flow condition and the dissipation behaviour of its different metabolites formed in soil under
field conditions was also studied. Field experiment was carried out in Research field of Department of vegetable
Science, and lab study was performed in Agrochemicals Residues Testing Laboratory, Department of Agronomy,
Chaudhary Charan Singh Haryana Agricultural University. Pyriproxyfen (Lano 10 EC) was applied on chilli crop
and soil at two doses i.e., 100 (T1) and 200 (T2) g a.i./ha. Chilli and soil samples were collected periodically on 0
(2h), 1, 3, 7, 10, 15, 30 and 45 days after application. Various sample preparation techniques i.e. QuEChERS,
Liquid-solid extraction (LSE) and Matrix solid phase dispersion (MSPD) were optimized for chilli and soil at
different fortification levels (0.005-0.1 μg/g). Maximum recoveries (83.1 to 104.8%) for chilli were obtained using
LSE, In soil, MSPD revealed 94.2 to 104.3% recoveries. The test samples were analysed over GC-MS/MS. A first
order dissipation kinetics was followed with half-lives ranged from 4.7 to 8.1 days in chilli treated with
pyriproxyfen under field and lab conditions and from 3.7 to 8.2 days in soil at two doses. The residues reached
below MRL value (0.02 mg/kg) on 45 day in chilli under both conditions. In case of soil residues were below
detection limit on 45 day in field samples and on 60 day in lab samples. Average reduction in residues due to
washing was in the range of 54-56% under field conditions and 35-47% under lab conditions. Residues in wash
water were ranged from 0.077 to 0.158 μg/mL in T1 and 0.091 to 0.316 μg/mL in T2 application under field
conditions and 0.041 to 0.138 μg/mL in T1 and 0.066 to 0.337 μg/mL in T2 under lab conditions, respectively.
During this study, six metabolites of pyriproxyfen were observed in soil namely 4-OH-PYR (A), POP (C), POPA
(E), 4-OH-POPA (F), PYPA (G) and PYPAC (H). Dissipation study of the metabolites revealed their appearance
on the day of pyriproxyfen application, reached to maximum concentration on 1 DAA in soil. All the metabolites
except 4-OH-PYR persisted for more than 30 days in soil with half-lives ranged from 2.6 to 30 days. Higher dose
was significantly more detrimental to honey bees. Leaching study do not showed any leaching potential of
pyriproxyfen and almost whole of applied pyriproxyfen was retained within 0-5 cm soil depth.