Laboratory and field studies were conducted on the oviposition behavior of the pathogen-vectoring mosquito, Culex quinquefasciatus, in response to the oviposition pheromone 6-acetoxy-5-hexadecanolide, produced from a renewable plant resource, Kochia scoparia (Chenopodiaceae) (plant-derived pheromone, PDP), and via an established synthetic route (synthetic oviposition pheromone, SOP). Responses to the oviposition cue skatole (3-methylindole), presented individually and in combination with the plant-derived and synthetic oviposition pheromone, were also studied. Both laboratory and field assays showed that PDP and SOP were equally attractive. Synergistic effects were observed with one combination of PDP and skatole combinations in laboratory assays. Synergy was also observed under field conditions. SOP and skatole combinations showed additive effects in laboratory assays, but were not tested in field bioassays. Although synergism has been previously demonstrated with combinations of SOP and polluted waters, the work presented here is the first example of synergy between a specific oviposition attractant and the oviposition pheromone. Furthermore, the efficacy of mosquito pheromone produced from a cheap, renewable botanical source has been demonstrated.

The oviposition pheromone for the pathogen-vectoring mosquitoes in the genus Culex (Diptera: Culicidae), that is, (5R, 6S)-6-acetoxy-5-hexadecanolide, is efficiently synthesized, in admixture with the inactive (5S,6R) enantiomer ( approximately 33% w/w), from the fixed oil extracted from the seeds of the summer cypress plant, Kochia scoparia (Chenopodiaceae), cultivated on an industrial scale. Oviposition bioassays using gravid females of Culex quinquefasciatus, a vector of filariasis in human beings, showed that the product was attractive, with activity comparable to that of a pure synthetic sample containing the same amount of the active enantiomer. Production of the pheromone in the form of a biologically active crude material via a cheap and renewable plant suitable for development as a new industrial crop provides the basis for control of Cx. quinquefasciatus and other congeneric vectors of pathogens in resource-poor areas of the world.

The kinetics of hydrolyses of methyl salicylate and methyl o-methoxybenzoate have been studied at various hydroxide ion concentrations ranging from 0.01 to 4.40 M for methyl salicylate and from 0.005 to 0.200 M for methyl o-methoxybenzoate at 35 °C. The observed rate constants are independent of [OH"] within the range 0.01-0.04 M and vary according to the equation fcobK¡ = A + B[OH"] + C[OH"]1 2 within the range 0.04-3.60 M for hydrolysis of methyl salicylate where A = fe3fe1[H20]/(le-1 + ft3), B = k2kJ(k-2 + kt), and C = k2kbK/(k^2 + k4). The observed rate constants for hydrolysis of methyl o-methoxybenzoate follow the equation feobed = B1[OH"] + C*[OH"]2 where B1 = k{k2/(k.í + k{) and C1 = kfk2K'¡(k-f + k2). The pH-independent observed rate constants are ~10* and ~105 times larger than the corresponding values for water-catalyzed cleavages of methyl benzoate and methyl o-methoxybenzoate, respectively. This rate enhancement has been attributed to the probable intramolecular general-base-catalyzed neutral hydrolysis of methyl salicylate. The ratios B/B1 and C/C1 have been found to be 0.0214 and 0.0004, respectively. The appearance of C and C1 terms in the kinetic equations has been attributed to the existence of the oxydianionic tetrahedral intermediates in the reaction mechanisms. The temperature dependence of hydrolysis of methyl salicylate has also been studied at two different OH" concentrations. The intramolecular general-base-catalyzed rate enhancement has been found to be due to a favorable AS*. The hydrolytic cleavage of methyl salicylate has been found to be sensitive to the ionic strength. The probable mechanisms for hydrolyses of both esters are considered.

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