Larvicidal activity of some secondary lichen metabolites against the mosquito Culiseta longiareolata Macquart (Diptera: Culicidae).

The larvicidal activity of some lichen metabolites, (+)-usnic acid, atranorin, 3-hydroxyphysodic acid and gyrophoric acid, against the second and third instar larvae of the mosquito Culiseta longiareolata were studied. All metabolites caused high larvicidal activities. When metabolites were compared on the basis of their LC(50) values, the order of increasing toxicity was as follows: gyrophoric acid (0.41 ppm) > (+)-usnic acid (0.48 ppm) > atranorin (0.52 ppm) > 3-hydroxyphysodic acid (0.97 ppm). However, when LC(90) values were compared, the order of toxicity was (+)-usnic acid (1.54 ppm) > gyrophoric acid (1.93 ppm) > 3-hydroxyphysodic acid (4.33 ppm) > atranorin (5.63 ppm). In conclusion, our results found that lichen secondary metabolites may have a promising role as potential larvicides.

Acaricidal activity of Satureja thymbra L. essential oil and its major components, carvacrol and gamma-terpinene against adult Hyalomma marginatum (Acari: Ixodidae).

The acaricidal activity of a volatile essential oil hydrodistillate of Satureja thymbra L. (Lamiaceae) and its major constituents, carvacrol and gamma-terpinene, were evaluated against field-collected unfed adult Hyalomma marginatum. The distillate was tested against this tick species at 5, 10, 20, and 40 microL/L while the two major components were each tested at 10 microL/L. Generally, tick mortality to the S. thymbra distillate increased with concentration and exposure time. Ticks exposed to vapors from cotton wicks containing at least 40 microL/L resulted in complete (100%) mortality at 3h. The lower concentrations provided >or=90% mortality at 3h post treatment with complete mortality at 24h. Knockdown was observed only in the carvacrol and gamma-terpinene treatments. Ticks exposed to carvacrol-treated wicks produced >93% knockdown at 3h but at 24h approximately 57% were dead. The gamma-terpinene treatment produced >or=90% knockdown at 105 min through 3h but at 24h only about 87% of the ticks were dead.

Effects of Two Temperature Storage Regimes on the Efficacy of 3 Commercial Gel Baits against the German Cockroach, Blattella germanica L. (Dictyoptera: Blattellidae).

BACKGROUND: To compare the effectiveness of 3 commercial gel bait formulations containing fipronil (Goliath(©) Cockroach Gel 0.05% AI), chlorpyrifos-A (Clean Bait(©) Gel, 2% AI), and chloropyrifos-B (Serpa(©) Gel 2% AI) against German cockroaches (Blattella germanica) when stored at 23(°)C and 30(°) C after treatment. METHODS: Laboratory bioassays consisted of placing groups of fifteen cockroaches (a random combination of adult, mixed sex and large nymphs-stage 6) into a 5 L cylindrical plastic container with one drop of product (avg 0.10 g ± 0.01 g) applied to a 76 mm x 26 mm glass microscope slide affixed to the bottom of each container (one product tested per container). Cumulative mortality was assessed at 6 h, 1, 2, 3, 4, and 5 d after application. To determine the further effects of storage temperature after treatment on residual activity of the gels, a drop of each product was applied to separate glass microscope slides and stored at either 23(°) C (warm) or 30(°) C (hot) under dark conditions for 0, 1, 7, 14, 30, 45, 60 and 90 d after application. RESULTS: Freshly applied baits (day 0) containing fipronil provided complete cockroach mortality (100%) within 5 d whereas chloryrifos-A and chlorpyrifos-B provided ≈72% and 88% mortality, respectively. Generally, cockroach mortality was greater when gels were stored at 30(°)C compared with 23(°) C. CONCLUSION: The fipronil gel formulation proved to be as efficacious as the chlorpyrifos gels and in some instances surpased the latter formulations depending on storage time and temperature by providing ≈90% mortality at 90 d post treatment.

Evaluation of temephos and chlorpyrifos-methyl against Culex pipiens (Diptera: Culicidae) larvae in septic tanks in Antalya, Turkey.

The larvicidal activity of chlorpyrifos-methyl and temephos was evaluated against Culex pipiens L. (Diptera: Culicidae) in septic tanks in Antalya, Turkey. Chlorpyrifos-methyl (Pyrifos MT 25 emulsifiable concentrate [EC] ) was evaluated at application rates of 0.04, 0.08, and 0.12 mg active ingredient (AI)/liter, and temephos (Temeguard 50 EC) was evaluated at 0.02, 0.04, and 0.06 mg (AI)/liter during a 21-d study. Generally, overall larval reduction in septic tanks from single- and multifamily dwellings treated with either larvicide was significantly greater than pretreatment levels and control tanks for the duration of the study. At 14 d posttreatment, duration of control was greatest in multifamily tanks treated with chlorpyrifos-methyl at the highest application rate with similar levels of control through 21 d for single-family dwellings (range 97-100%). Septic tanks from both types of family dwellings treated at the highest application rate of temephos resulted in >90% reduction through day 21 (range 91-100%). Laboratory bioassays of septic tank water treated at field application rates, without daily dilution, revealed that complete larval mortality was achieved for 21 d at each application rate and formulation. It is thought that daily addition of water and organic matter to the septic tanks in the single and multifamily dwellings influenced the duration of effectiveness of the larvicides.

Efficacy of diflubenzuron, a chitin synthesis inhibitor, against Culex pipiens larvae in septic tank water.

The mosquito Culex pipiens L. is an important pest in urban and suburban areas in many parts of the world. Septic tanks are the most important habitats supporting the production of this species in the city of Antalya, southwestern Turkey. Diflubenzuron, in a 25% wettable powder (Du-dim 25 WP), and a 4% granular formulation (Du-dim 4 G) was evaluated against late 2nd to early 3rd instars of Cx. pipiens in single-family septic tanks. Both formulations were tested at 0.01, 0.02, and 0.03 mg (AI)/liter. The results indicated that both formulations applied at the rate of 0.02 and 0.03 mg (AI)/liter achieved 100% adult inhibition, at intervals of 7, 14, 21, and 28 days after treatment. Septic tanks treated with 0.01 mg (AI)/liter WP formulation resulted in complete (100%) adult inhibition through 14 days, whereas the G formulation gave the same effect through 21 days posttreatment at this rate.

Larvicidal activity of a botanical natural product, AkseBio2, against Culex pipiens.

A botanical natural product, AkseBio2, was evaluated for its larvicidal effect against Culex pipiens under laboratory conditions. The product exhibited strong larvicidal activity and caused >90% mortalities in both the young (first-second) and the older (third-fourth) larval stages of the species at 24 h at the doses of 25 and 50 ppm. However, it was determined that the young larval stages were more susceptible to the product in comparison with the older larval stages. The results suggest that the product is promising as a larvicide against C. pipiens and could be useful in the search of new larvicidal natural compounds.

Use of the Drosophila wing spot test in the genotoxicity testing of different herbicides.

Four herbicides, namely propanil, maleic hydrazide, glyphosate, and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were investigated for genotoxicity in the wing spot test of Drosophila melanogaster. The herbicides were administered by chronic feeding to 3-day-old larvae. Two different crosses, a standard (ST) and a high-bioactivation (HB) cross, involving the flare-3 (flr(3)) and the multiple wing hairs (mwh) markers, were used. The HB cross uses flies characterized by an increased cytochrome P-450-dependent bioactivation capacity, which permits a more efficient biotransformation of promutagens and procarcinogens. In both crosses, the wings of the two types of progeny, which are inversion-free marker heterozygotes and balancer heterozygotes, were analyzed. Maleic hydrazide and glyphosate proved to be more genotoxic in the ST cross, whereas propanil appeared to be slightly more genotoxic in the HB cross. On the other hand, the herbicide 2,4,5-T increased the mutation frequency for only the small single spots in the ST cross.

Induction of an adaptive response in Drosophila imaginal disc cells exposed in vivo to low doses of alkylating agents.

The adaptive response of Drosophila larvae to three alkylating agents (ethyl methanesulfonate, methyl methanesulfonate and N-nitroso-N-ethylurea) has been studied in the wing spot test. The experimental procedure included a 24 h pretreatment of 2-day-old larvae with two different adaptive doses followed by a challenge dose applied until the end of development. The genotoxic effects were analysed in trans-heterozygous larvae for the third chromosome recessive markers multiple wing hairs (mwh) and flare (flr(3)). Genetic changes induced in somatic cells of the wing imaginal discs led to loss of heterozygosity, expressed as mutant clones of the genetic markers used. From our results it appears that the adaptive doses clearly reduce the frequency of mutant clones induced by the challenge dose. As far as we know, this is the first time that the existence of an adaptive response to alkylating agents after Drosophila larval treatment has been reported using the wing spot assay.

Genotoxicity testing of five herbicides in the Drosophila wing spot test.

Four triazine herbicides: amitrole, metribuzin, prometryn and terbutryn, and the bipyridal compound diquat dibromide have been evaluated for genotoxicity in the wing somatic mutation and recombination test of Drosophila melanogaster, following standard procedures. Third-instar larvae trans-heterozygous for the third chromosome recessive markers multiple wing hairs (mwh) and flare-3 (flr(3)) were chronically fed with different concentrations of the test compounds. Feeding ended with pupation of the surviving larvae. Genetic changes induced in somatic cells of the wing's imaginal discs lead to the formation of mutant clones on the wing blade. Point mutation, chromosome breakage and mitotic recombination produce single spots; while twin spots are produced only by mitotic recombination. Exposure to 0.5 mM and 1 mM of amitrole clearly increased the frequency of small single, large single and total spots. Terbutryn, at the concentration of 5 mM, induced a slight increase in the frequency of small single and total spots, but this result could be false positive. The other three herbicides tested did not show any genotoxic effect. When heterozygous larvae for mwh and the multiple inverted TM3 balancer chromosomes were treated, significant increases in the frequency of mutant spots were only detected for amitrole. The observed spot frequencies were lower than those found in mwh/flr(3)50%) of the total spot induction was due to mitotic recombination.

Genotoxicity studies on the phenoxyacetates 2,4-D and 4-CPA in the Drosophila wing spot test.

The phenoxyacetates 2,4-D and 4-CPA were evaluated for genotoxicity using the Drosophila melanogaster wing spot test, which assesses for somatic mutation and recombination events. Third-instar larvae trans-heterozygous for two recessive mutations affecting the expression of wing trichomes, multiple wing hairs (mwh), and flare (flr) were treated by chronic feeding with different concentrations of the two chemicals. Feeding lasted until pupation of the surviving larvae and the genotoxic effects induced were evaluated in adults for the appearance of wing-blade cell clones with the mwh, flr, or mwh-flr phenotypes. Exposure to 2,4-D, at the highest concentration evaluated (10 mM), induced a weak but significant increase in the frequency of two of the categories of recorded spots: large single and total spots; in contrast, the 4-CPA treatments failed to induce any significant increase in the frequency of evaluated spots. When the heterozygous larvae for mwh and the multiple inverted TM3 balancer chromosome were treated with the chemicals, no increases were detected, either after the 2,4-D nor the 4-CPA treatments.