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Diflubenzuron (Dimilin(RTM)): Environmental effects and biochemical mode -of-action
Abstract
The effects of a single aerial application of diflubenzuron (Dimilin$\sp\circler$ over Warwick State Forest, MA, on nontarget aquatic macroinvertebrates of vernal pools and a stream was studied. Vernal pool populations which significantly decreased after the treatment were mosquito (Culicidae) pupae and Cyclops. No impact was demonstrated for the other abundant taxa in these vernal pools (mosquito larvae, water mites (Hydrarchanidae), tardigrades and springtails (Collembola)). The stream nontarget populations which significantly decreased after the treatment include 3 taxa of black flies (Prosimulium mixtum/fuscum, Simulium vernum & S. vittatum; Diptera: Simuliidae). No impact was demonstrated for the other abundant taxa (Amphinemora, Leuctra, Ostrocerca (Plecoptera); Siphlonurus (Ephemeroptera); Rhyacophila, Ironoquia, Lepidostoma, Neophylax (Trichoptera): Chironomidae (Diptera)) nor for a particular size class of these taxa. The timing of population growth and development, and pesticide exposure by filter-feeding are the reasons used to explain these results. A laboratory acute toxicity study of diflubenzuron with mosquito larvae (Aedes aegypti; Culicidae) under different water acidities was conducted. Low pH treatments (pH = 4.5) resulted in 100 fold higher mortality of 4-day-old larvae (LC$\sb{50} = 5\ {\rm n}M$) compared with less acid water (pH = 6.6; LC$\sb{50} = 500\ {\rm n}M$). The synergist action of diflubenzuron with lowered pH has implications for prediction of nontarget impact in habitats exposed to acid rain. A diflubenzuron biochemical mode-of-action study was conducted to determine if: (1) dolichol is present in the chitin-synthesizing plasma membrane of Chironomus tentans cell line, (2) dithiocarbanilates (i.e. nucleoside-transport inhibitors that affect membrane characteristics) inhibit chitin synthesis as does diflubenzuron in C. tentans, and, (3) diflubenzuron has a binding affinity for dolichol pyrophosphate N-acetylglucosamine (Dol-PP-GlcNAc). Plasma membrane was isolated from C. tentans by the method of Chaney & Jacobson (1983). No dolichol was found in this preparation, however, the preparation was never characterized as plasma membrane. Low cell culture growth prevented further study. Dol-PP-GlcNAc was produced from rat liver enzymes, however, diflubenzuron quantification limits (HPLC, ELISA) were too low to conduct a binding affinity study.
Subject Area
Entomology|Toxicology|Environmental science
Recommended Citation
Martin, Paula J. S, "Diflubenzuron (Dimilin(RTM)): Environmental effects and biochemical mode -of-action" (1993). Doctoral Dissertations Available from Proquest. AAI9408307.
https://scholarworks.umass.edu/dissertations/AAI9408307