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Clothing impregnations of dibutylphthalate and permethrin as protectants against a chigger mite, Eutrombicula hirsti (Acari: Trombiculidae).

A field study to compare the effects of wearing military uniforms treated with permethrin or dibutylphthalate as protection against the chigger Eutrombicula hirsti (Sambon) was conducted in northern Queensland, Australia, during November 1990. Volunteers who wore treated uniforms received significantly fewer chigger attachments than individuals who wore untreated uniforms. Australian military uniforms treated with dibutylphthalate provided a 97.6% increase in protection, whereas uniforms treated with 0.058-0.101 mg/cm2 permethrin provided 96.4% protection. U.S. Army uniforms treated with 0.125 mg/cm2 permethrin provided 83.2% protection. The differences between the clothing treatments were not significant. The results show that wearing clothing impregnated with either compound is an effective method for personal protection against E. hirsti.

Animals↗

Potential use of pyriproxyfen for control of Aedes aegypti (Diptera: Culicidae) in Iquitos, Perú.

The effects of pyriproxyfen were tested against a local population of Aedes aegypti (L.) in Iquitos, Perú. Bioassays showed that, when applied to late instars, pyriproxyfen prevented adult emergence at extremely low concentrations (LC50 = 0.012 ppb). There was no adult emergence from water sampled from storage tanks that had been seeded with the equivalent of 50-83 ppb (AI) pyriproxyfen. Five months after treatment, despite constant dilution of these tanks, water sampled from these sources continued to be lethal to larvae and pupae. Additional studies, carried out in the laboratory, showed that groups of five or 20 female blood-fed mosquitoes, exposed to residues of approximately 0.003 g (AI) pyriproxyfen/m2, could transfer enough chemical to new oviposition sites to prevent approximately 80% of adult emergence from larvae developing in that previously uncontaminated water. Moreover, although the fecundity of the adult females used as the transfer vehicles in these tests was unaffected, the subsequent eclosion of the eggs that these mosquitoes laid was decreased by 70-90%. It also was shown that, at very high concentrations (>30,000 ppb), pyriproxyfen-treated water sources were as likely to be used as oviposition sites as untreated sources. These data suggest that treated sites might act as sinks for mosquito reproduction and moreover that such sites might act as dissemination sources for the horizontal transfer of larvicides to new environments by mature females. We review the literature on the environmental and human health effects of this compound and discuss its potential for use as a mosquito control agent in the field.

Aedes↗

Enhanced degradation and toxicity reduction of dihexyl phthalate by Fusarium oxysporum f. sp. pisi cutinase.

AIMS: This research aims to investigate the efficiency of two lipolytic enzymes--fungal cutinase and yeast esterase--upon the biodegradation of dihexyl phthalate (DHP). METHOD AND RESULTS: During the enzymatic degradation of DHP dissolved in methanol, several degradation products were detected and their time-course changes were monitored using GC/MS. The DHP-degradation rate of cutinase was surprisingly high; i.e. almost 70% of the initial DHP (500 mg l(-1)) was decomposed within 4.5 h. Although the same amount of esterase was employed, more than 85% of the DHP remained after 3 days. Almost all the DHP was converted by cutinase into 1,3-isobenzofurandione (IBF), whereas hexyl methyl phthalate and IBF were abundantly produced by esterase. In addition, the toxicities of the DHP-degraded products by esterase were evaluated using various recombinant bioluminescent bacteria, which caused oxidative and protein damage, whereas the hydrolysis products from cutinase never caused any cellular damage in the methanol-containing reaction system. CONCLUSIONS: Cutinase starts to act as a DHP-degrader much earlier and faster than esterase, with high stability in ester-hydrolytic activity, therefore a plausible approach to the practical application of cutinase for DHP degradation in the DHP-contaminated environments may be possible. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the enhanced degradation and detoxification of DHP using Fusarium oxysporum f. sp. pisi cutinase.

Biodegradation, Environmental↗

Control of haematophagous flies on equines with permethrin-impregnated eartags.

The efficacy of 10% (w/w) permethrin impregnated eartags for the control of the haematophagous fly pests Stomoxys calcitrans L., Haematopota dissimilis Meigen and Hippobosca maculata Leach on equines in India was determined. The tags were found to be effective for 1-2 months against S. calcitrans and H. dissimilis but completely ineffective against H. maculata. No tags were lost during the study. Tags can be used as part of an integrated control programme. This is the first reported use of eartags for control of haematophagous flies on horses.

Animals↗

Metabolism of dimethylphthalate by Micrococcus sp. strain 12B.

During growth of Micrococcus sp. strain 12B with dimethylphthalate, 4-carboxy-2-hydroxymuconate lactone (CHML, X) and 3,4-dihydroxyphthalate-2-methyl ester (XI) were isolated from culture filtrates. CHML is the lactone of intermediate 4-carboxy-2-hydroxymuconate (IX). Accumulation of XI which is not a substrate for 3,4-dihydroxyphthalate-2-decarboxylase in strain 12B afforded an easy access to the preparation of 3,4-dihydroxyphthalate.

Insect Repellents↗