A high-throughput screening method to identify potential pesticides for mosquito control.

Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, 1600 SW 23rd Dr., Gainesville, FL 32608, USA.
Journal of Medical Entomology (Impact Factor: 1.86). 04/2009; 46(2):335-41. DOI: 10.1603/033.046.0219
Source: PubMed

ABSTRACT Mosquitoes that transmit human diseases are of major importance to the international public health community. Pesticides remain a major component of integrated programs to control these medically important species. However, very few types of pesticides are currently registered for mosquito control. A high-throughput screening method using first-instar larvae of Aedes aegypti was created and evaluated in our laboratory to quickly screen large numbers of chemicals for activity against mosquitoes. LC50 values of a representative group of compounds were determined using this high-throughput screening method and compared with LD50 values determined by topical application against female adults of Ae. aegypti. Our results show that this high-throughput screening method is suitable for screening large numbers of candidate chemicals quickly to identify effective compounds.

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    ABSTRACT: In this study, Angelica dahurica and Angelica pubescentis rot essential oils were investigated as pest management perspective and root samples were also analyzed genetically using the nuclear ribosomal internal transcribed spacer (ITS) region as a DNA barcode marker. Angelica pubescentis root essential oil demonstrated moderate antifungal activity against Colletotrichum acutatum, C. fragariae, and C. gloeosporioides, whereas A. dahurica root essential oil did not show antifungal activity. Conversely, A. dahurica root essential oil demonstrated better deterrent and insecticidal activity against yellow fever mosquito, Aedes aegypti and azalea lace bugs, Stephanitis pyrioides than A. pubescentis root oil. The major compounds in the A. dahurica oil were found as a-pinene (46.3%), sabinene (9.3%), myrcene (5.5%), 1-dodecanol (5.2%) and terpinen-4-ol (4.9%). a-Pinene (37.6%), p-cymene (11.6%), limonene (8.7%) and cryptone (6.7%) were the major compounds found in the A. pubescentis oil. In mosquito bioassays, 1-dodecanol and 1-tridecanol showed anti-biting deterrent activity similar to the positive control DEET (N,N-diethyl-3-methylbenzamide) at 25 nmol/cm2 against Aedes aegypti, whereas only 1-tridecanol showed repellent activity in human based cloth patch bioassay with minimum effective dosages (MED) of 0.086 ± 0.089 mg/cm2 (DEET: 0.007 ± 0.003 mg/cm2). In larval bioassays, 1-tridecanol was more toxic with LC50 value of 2.1 ppm than 1-dodecanol having LC50 value of 5.2 ppm against 1-day old Ae. aegypti larvae. 1-Dodecanol and 1-tridecanol could be useful for the natural mosquito control agents.
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    ABSTRACT: Artemisia argyi, A. feddei, A. gmelinii, A. manshurica, and A. olgensis (Asteraceae) were collected in Far East Russia. Oils were hydrodistilled and simultaneously analyzed by GC-FID and GC/MS. Main constituents were found as follows in Artemisia oils: selin-11-en-4a-ol (18.0%), 1,8-cineole (14.2.0%), artemisia alcohol (12.9%), borneol (9.7%) in A. argyi; camphor (31.2%), 1,8-cineole (17.6%), a-thujone (5.7%) in A. feddei; longiverbenone (12.0%), isopinocamphone (8.9%), 1,8-cineole (6.7%), camphor (5.8%), trans-p-menth- 2-en-1-ol (5.3%) in A. gmelinii; germacrene D (11.2%), rosifoliol (10.1%), caryophyllene oxide (6.8%), eudesma-4(15),7-dien-1b-ol (5.6%) in A. manshurica; eudesma-4(15),7-dien-1b-ol (6.9%), caryophyllene oxide (5.6%), guaia-6,10(14)-dien-4b-ol (5.1%) and hexadecanoic acid (5.0%) in A. olgensis. Oils were subsequently submitted for antifungal and antimosquito evaluations. Artemisia species oils showed biting deterrent effects in Aedes aegypti and Artemisia gmelinii oil with the most active biting deterrence index values of 0.82 ± 0.1 at 10 mg/mL. Larval bioassay of A. gmelinii and A. olgensis oils showed higher larvicidal activity against Ae. aegypti larvae with LD50 values of 83.8 (72.6 – 95.7) ppm and 91.0 (73.8 – 114.5) ppm, respectively. Antifungal activity was evaluated against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides using direct overlay bioautography assay and all showed nonselective weak antifungal activity. Antioxidant evaluation of the oils was performed by using b-carotene bleaching, Trolox equivalent and DPPH tests. The tested Artemisia oils demonstrated moderate antioxidant activity.
    Records of Natural Products 01/2014; 8(3):242-261. · 1.56 Impact Factor
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    ABSTRACT: Twenty trifluoromethylphenyl amides were synthesized and evaluated as fungicides and as mosquito toxicants and repellents. Against Aedes aegypti larvae, N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-3,5-dinitrobenzamide (1e) was the most toxic compound (24h LC50 1940nM), while against adults N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-2,2,2-trifluoroacetamide (1c) was most active (24h LD50 19.182nM, 0.5μL/insect). However, the 24h LC50 and LD50 values of fipronil against Ae. aegypti larvae and adults were significantly lower: 13.55nM and 0.787×10(-4)nM, respectively. Compound 1c was also active against Drosophila melanogaster adults with 24h LC50 values of 5.6 and 4.9μg/cm(2) for the Oregon-R and 1675 strains, respectively. Fipronil had LC50 values of 0.004 and 0.017μg/cm(2) against the two strains of D. melanogaster, respectively. In repellency bioassays against female Ae. aegypti, 2,2,2-trifluoro-N-(2-(trifluoromethyl)phenyl)acetamide (4c) had the highest repellent potency with a minimum effective dosage (MED) of 0.039μmol/cm(2) compared to DEET (MED of 0.091μmol/cm(2)). Compound N-(2-(trifluoromethyl)phenyl)hexanamide (4a) had an MED of 0.091μmol/cm(2) which was comparable to DEET. Compound 4c was the most potent fungicide against Phomopsis obscurans. Several trends were discerned between the structural configuration of these molecules and the effect of structural changes on toxicity and repellency. Para- or meta- trifluoromethylphenyl amides with an aromatic ring attached to the carbonyl carbon showed higher toxicity against Ae. aegypti larvae, than ortho- trifluoromethylphenyl amides. Ortho- trifluoromethylphenyl amides with trifluoromethyl or alkyl group attached to the carbonyl carbon produced higher repellent activity against female Ae. aegypti and Anopheles albimanus than meta- or para- trifluoromethylphenyl amides. The presence of 2,6-dichloro- substitution on the phenyl ring of the amide had an influence on larvicidal and repellent activity of para- trifluoromethylphenyl amides.
    Pesticide Biochemistry and Physiology 09/2013; 107(1):138–147. · 2.11 Impact Factor

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