Alfonso Vásquez-López

Chemical characterization and mosquito larvicidal activity of essential oil from leaves of Persea americana Mill (Lauraceae) against Culex quinquefasciatus (Say)

Abstract Objective To determine chemical composition and mosquito larvicidal activity of essential oil from dried leaves of Persea americana against Culex quinquefasciatus. Methods About 20 larvae in each group were used for larvicidal assays. The mortality, relative growth index, larval and pupal duration and viability were estimated. The essential oil was analyzed by solid phase microextraction using gas chromatography coupled to mass spectrometry. Results The most abundant compounds were estragole (61.86%), sabinene (15.16%) and 1R-α-pinene (14.25%). The essential oil inhibited mosquito larvae growth up to 26.73% [relative growth index (RGI) = 0.74)] and 16.83% (RGI = 0.84) at 800 and 50 mg/L respectively, while the untreated control and group treated with polysorbate 20 showed the RGI of 1.01. The viability of larvae to pupae decreased 53.75% when used 800 mg/L essential oil causing prolongation of development of 14.14 days, while the control had durability in its development of 12 days. In the pupae-adult phase, when used 800 and 50 mg/L of essential oil, 22.36% and 21.81% adults were formed, and there was prolongation of 15.88 days and delay of 13.62 days respectively; however the control showed duration of 14.63 days. Mortality at the end of the experiment was recorded as 57.50% with treatment of 800 mg/L and gradually decreased to 40% with treatment of 50 mg/L essential oil. Conclusions The study demonstrated that the larvicidal activity of essential oil of Mexican avocado inhibited the normal growth and development of mosquito larvae, prolonged larval and pupal duration.

A new species of Aeolothrips (Thysanoptera: Aeolothripidae) from mango crops in Oaxaca, Mexico.

ABSTRACT We describe Aeolothrips romanruizi sp. nova that has been recently discovered in mango orchards in the Isthmus region of Oaxaca in southern Mexico. Aeolothrips romanruizi sp. nova exhibits an ornamentation of the mesonotum and metanotum very different from others in this genus, except A. microstriatus, which is similarly ornamented; but these 2 species differ in forewing color pattern, body size and some other characters of chaetotaxy. A key to the Aeolothrips species of Central America and Mexico is provided.

Argemone mexicana (Papaverales: Papavaraceae) as an Alternative for Mosquito Control: First Report of Larvicidal Activity of Flower Extract

Abstract Culex quinquefasciatus Say (Diptera: Culicidae), an arboviral and filarial vector, is one of the most widespread mosquitoes in the world. The indiscriminate use of synthetic chemical insecticides has led to the development of resistance in mosquito populations worldwide. The effect of continuous exposure to crude extracts of Argemone mexicana, the Mexican poppy, on the development and growth stages of second-instar larvae of the mosquito was studied, along with qualitative chemical analysis of the different plant parts. Inhibition, mortality, and larval and pupal duration phases were assessed. Second-instar mosquito larvae were exposed to crude ethanol extracts of flowers, stems, and seeds. Flower extract exhibited the strongest larvicidal activity with LC50 and LC90 values after 24 h of exposure of 18.61 and 39.86 ppm, respectively, and 9.47 and 21.76 ppm after 48 h. Extracts from stem and seeds were significantly less effective. The flower extract registered a Growth Inhibition Index of 0.01 at 25 ppm, with stems and seeds registering 0.05 and 0.08, respectively, at 100 ppm (control group 1.02). Qualitative chemical analysis by thin-layer chromatography showed characteristic spots indicating the presence of alkaloids and flavonoids and phytochemical screening showed the presence of alkaloids, anthraquinones, flavonoids, tannins, and terpenoids in the various crude extracts. This is the first report of the effectiveness of an ethanol flower extract of A. mexicana on Cx. quinquefasciatus; it can be considered a promising alternative control for this mosquito species.