Degradation of Phenothrin in Stored Wheat Grains

Abstract

14C-Labeled (+)-traps and (+)-cis isomers of phenothrin [3-phenoxybenzyl (+)-cis, traps-chrysanthemate] were each applied at the concentration of 4 ppm to wheat grains 11% moisture content, and stored at 15 or 30C in the dark. Both traps and cis were decomposed slowly, and 79 and 87% of the applied radiocarbon remained intact in after 12-month storage at 30C, respectively. Both isomers majorly metabolized via hydrolysis of ester linkage, oxidation of the benzyl alcohol to the benzoic acid and of the benzoic acid. The joint application with piperonyl butoxide and fenitrothion inhed the degradation of phenothrin isomers to some extent. The phenothrin isomers and their decomposition products were mainly located at seed coat during 12-month storage, and residue levels of both isomers in flour and bran were 0.77 and 11.4 The phenothrin residues in flour somewhat decreased through the baking process, leaving of phenothrin isomers in bread. These findings were compared with those of 14C-m which was rapidly decomposed to desmethylmalathion, malathion-monoacids, -and 14CO2i with respective half-lives of 8 and 1.1 months at 15 and 30C .

Cypermethrin and fenvalerate residues in stored wheat and milled fractions

“…The reductions of 12 to 13% in fenvalerate and 15 to 21% in cypermethrin residues, found in the present studies, may be due to a higher baking temperature and longer baking time used in the present studies. The present results agree with 13-30% reduction in phenothrin residues observed by Nambu et al (1981). However, the reduction is much less than observed for methyl phoxim (79-100%) or malathion (80-100%) reported by Alnaji and Kadoum (1981).…”

“…Bengston et al (1983) found 0.70, 3.3, and 0.08 mg kg"1 fenvalerate in wheat, bran, and flour (endosperm), respectively, 10 months after an application of 1 mg kg"1 fenvalerate to wheat. A slow decline in residues of cypermethrin and fenvalerate observed in the present studies is similar to that observed for phenothrin, deltamethrin, permethrin, and fenvalerate (Bengston et al, 1983;Hargreaves et al, 1982;Noble et al, 1982;Nambu et al, 1981). However, the results differ from those of Ardley and Halls (1979) who could not detect phenothrin residues in bran or bread made about 3 weeks after an application of 8 mg kg"1 phenothrin to wheat.…”

Analysis of the synthetic pyrethroids, permethrin and 1(R)-phenothrin, in grain using a monoclonal antibody-based test

“…l(fi)-Phenothrin has been assessed in intensive field trials in a number of countries (Bengston et al, 1983; Desmarchelier et al, 1987). Although it is not as potent as bioresmethrin and tends to produce higher residue levels in flour and bread (Nambu et al, 1981), it is somewhat less expensive and shows better persistence on grain stored for long periods. Other applications of this compound include disinfection of aircraft and household surface insecticide sprays.…”

Photoinduced Oxidation of the Insecticide Phenothrin on Soil Surfaces

“…Although the use pattern of phenothrin is limited to noncrop areas, the possibility of its release to the environment should be envisaged in case of residential exposures from outdoor lawn and garden sprays against groundling or flying insect pests. Several studies on phenothrin have been carried out to assess its environmental fate , as well as mammalian and fish metabolism. , Furthermore, the identities of its transformation products in air and on surface samples taken following indoor applications have been reported by using high-resolution gas chromatography and mass spectrometry. , However, much less information is currently available for its photodegradation behavior including oxidation mechanisms on soil surfaces because of its very limited entry into the environment.…”