The aim of this study was to assess the effect of several insect growth regulators (IGRs) on the nontarget soil arthropod Folsomia
candida (Collembola). The survival and reproduction rates of F. candida were evaluated after 28 days of exposure to six IGRs
(methoprene, fenoxycarb, precocene II, tebufenozide, hexaflumuron and teflubenzuron) and to one herbicide (diuron) in artificial
soil. The differences in the sensitivity of F. candida to these different substances are high. The chitin synthesis inhibitors
teflubenzuron and hexaflumuron were the most toxic compounds with an EC50 of 0.05 mg/kg (dry weight) for teflubenzuron and an
EC50 of 0.6 mg/kg for hexaflumuron. Teflubenzuron is toxic for F. candida at concentrations that are probably close to
environmental levels of this insecticide. Inhibition of reproduction is strongly related to adult survival for the juvenile hormone
agonist methoprene and for the antijuvenile hormone precocene II, with an EC50 of 173 mg/kg and a LC50 of 178 mg/kg for
methoprene and an EC50 of 15 mg/kg and a LC50 of 26 mg/kg for precocene II. Fenoxycarb, another juvenile hormone analog,
showed a dose–response curve for mortality different from that of methoprene; at concentrations such as 3052 mg/kg no effect on
adult survival was observed. However, the EC50 value of 113 mg/kg is of the same order of magnitude as that obtained for
methoprene. A test with compressed soil contaminated with fenoxycarb was conducted to observe parameters such as numbers of
eggs laid and juveniles hatched. No differences were observed between these two endpoints for fenoxycarb. An EC50 of 109 mg/kg
was obtained for the ecdysone agonist tebufenozide. The herbicide diuron showed a relatively high toxicity for F. candida with an
EC50 of 20 mg/kg. Our results show that some of the tested IGRs can have effects on Collembola at environmentally relevant
concentrations (toxicity/exposure ratios o5 for teflubenzuron, hexaflumuron, and diuron).
r 2005 Elsevier Inc. All rights reserved.
The aim of this study was to assess the effect of several insect growth regulators (IGRs) on the nontarget soil arthropod Folsomiacandida (Collembola). The survival and reproduction rates of F. candida were evaluated after 28 days of exposure to six IGRs(methoprene, fenoxycarb, precocene II, tebufenozide, hexaflumuron and teflubenzuron) and to one herbicide (diuron) in artificialsoil. The differences in the sensitivity of F. candida to these different substances are high. The chitin synthesis inhibitorsteflubenzuron and hexaflumuron were the most toxic compounds with an EC50 of 0.05 mg/kg (dry weight) for teflubenzuron and anEC50 of 0.6 mg/kg for hexaflumuron. Teflubenzuron is toxic for F. candida at concentrations that are probably close toenvironmental levels of this insecticide. Inhibition of reproduction is strongly related to adult survival for the juvenile hormoneagonist methoprene and for the antijuvenile hormone precocene II, with an EC50 of 173 mg/kg and a LC50 of 178 mg/kg formethoprene and an EC50 of 15 mg/kg and a LC50 of 26 mg/kg for precocene II. Fenoxycarb, another juvenile hormone analog,showed a dose–response curve for mortality different from that of methoprene; at concentrations such as 3052 mg/kg no effect onadult survival was observed. However, the EC50 value of 113 mg/kg is of the same order of magnitude as that obtained formethoprene. A test with compressed soil contaminated with fenoxycarb was conducted to observe parameters such as numbers ofeggs laid and juveniles hatched. No differences were observed between these two endpoints for fenoxycarb. An EC50 of 109 mg/kgwas obtained for the ecdysone agonist tebufenozide. The herbicide diuron showed a relatively high toxicity for F. candida with anEC50 of 20 mg/kg. Our results show that some of the tested IGRs can have effects on Collembola at environmentally relevantconcentrations (toxicity/exposure ratios o5 for teflubenzuron, hexaflumuron, and diuron).r 2005 Elsevier Inc. All rights reserved.
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