Transport and kinetics of diflubenzuron and pyriproxyfen in the beet armywormSpodoptera exigua and its predatorPodisus maculiventris |
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Authors: | P De Clercq E Viuela G Smagghe D Degheele |
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Institution: | (1) Laboratory of Agrozoology, Faculty of Agricultural and Applied Biological Sciences, University of Gent, B-9000 Gent, Belgium;(2) Unidad de Protección de Cultivos, E.T.S.I. Agrónomos, Ciudad Universitaria, E-28040 Madrid, Spain;(3) Laboratory of Agrozoology, Faculty of Agricultural and Applied Biological Sciences, University of Gent, Coupure links 653, B-9000 Gent, Belgium |
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Abstract: | Transport and retention of the insect growth regulators (IGRs) diflubenzuron and pyriproxyfen in larvae of the beet armywormSpodoptera exigua (Hübner) and in nymphs of the predatory bugPodisus maculiventris (Say) were investigated. In a first experiment, the retention of orally administered 14C]radiolabeled isotopes of both compounds in fifth-instar larvae of the beet armyworm was studied. Rate of excretion of both
IGRs inS. exigua caterpillars was high, with a 50% excretion time of approximately 6 h after intake. In a second experiment, the transport
of the compounds from prey to predator and their retention inside the predator were studied. Fifthinstar nymphs ofP. maculiventris were allowed to feed on caterpillars that had been given contaminated food. For both diflubenzuron and pyriproxyfen, more
than 80% of the amount of radiolabel applied was recovered in consumed prey. Low levels of radioactivity (c. 3% of the applied amount of radiolabel) were also found in the fluid regurgitated by the prey larvae when attacked by the
predatory bugs. Relatively small amounts of radiolabel (c. 8 and 15% of the amount orally applied to the prey for diflubenzuron and pyriproxyfen, respectively) were ingested byP. maculiventris nymphs when feeding on beet armyworm caterpillars. The data suggest that the predators did not use gut content as food. The
pattern of excretion in nymphs ofP. maculiventris differed between compounds. For diflubenzuron, there was a drastic decrease of radioactivity inside the predator body of
around 40% within the first 6 h and then the level of retained radiolabel remained stable at 3–4% up to 72 h. For pyriproxyfen,
a slow decrease of radioactivity inside the body was observed and at 72 h only 2% of the applied quantity was detected. Results
of this study are discussed in relation to the findings from previous studies on the toxicity of both IGRs toP. maculiventris. |
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Keywords: | insect growth regulators diflubenzuron pyriproxyfen Podisus maculiventris Heteroptera predation Spodoptera exigua Lepidoptera side-effects |
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