The repeated use of permethrin and other insecticides for the control of head lice, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), during past decades has resulted in the development of marked levels of resistance. Thus, new alternative insecticides are needed for the control of head lice. We studied the fumigant and repellent properties of essential oils from 16 native and exotic plants in Argentina, and 21 chemical components against permethrin-resistant head lice from Argentina. With a direct vapor-exposure bioassay, the most effective oil was from the native Myrcianthes cisplatensis Cambess (Myrtaceae) with a time to 50% knockdown (KT50) of 1.3 min, followed by exotic species, Eucalyptus cinerea F.V. Muell., Eucalyptus viminalis Labill., and Eucalyptus saligna Smith. with KT50 values of 12.0, 14.9, and 17.4 min, respectively. The most effective components were 1,8-cineole and anisole, with KT50 values of 11.1 and 12.7 min, respectively. Regression analysis of KT50 values and vapor pressures and water-partition coefficients for the essential oil components revealed that the most effective fumigants were among the more volatile components. Repellency assays indicated that the essential oil from Mentha pulegium L. and its benzyl alcohol component were the most effective repellents, having repellency indices of 75.5 and 57.8%, respectively. Thus, some Argentinean plants contain essential oils and components that function as fumigants or as repellents and thereby show potential for development of new control products for head lice.
T-4464 Buffelgrass (Cenchrus ciliaris L.) is an introduced grass used extensively for restoring forage capacity of denuded shrublands in the arid Chaco region in central western Argentina. Currently, the technique of roller chopping and simultaneous buffelgrass seeding is widespread, but information is lacking about its effects on forage production and other vegetation attributes at the regional scale. The purpose of our study was to compare grass yield; vegetation cover and density; and species richness, diversity, and evenness, between roller chopping and simultaneous buffelgrass seeding with nontreated native degraded shrublands. Eight sites, including matched pairs of treated and nontreated areas, were studied. Grass yield, total perennial grass cover, and total perennial grass density were higher (P , 0.05) on treated areas. Increase in grass yield on treated areas compared with nontreated areas was related to the increase in total perennial grass cover due to added buffelgrass cover (r 2 ¼ 0.79). Shrub cover was lower (P , 0.05) on treated areas, but shrub density was not different between treatments (P. 0.05). Nonsignificant differences (P. 0.05) between treated and nontreated areas were detected in tree cover and density, species number, diversity index, and evenness. The results of this study indicate that, in the short term, roller chopping and simultaneous buffelgrass seeding produces rapid increases in grass cover and grass yield, and a drastic reduction in shrub cover without affecting species diversity on degraded shrublands of the arid Chaco region of Argentina. Resumen El buffel T-4464 (Cenchrus ciliaris L.) es un pasto introducido, utilizado para restaurar la capacidad forrajera de matorrales degradados en el sector centro-occidental de la regió n del Chaco á rido, Argentina. En la actualidad el rolado y siembra simultá nea de buffelgrass está ampliamente difundido en la regió n. Sin embargo, se carece de informació n a nivel regional, relacionada con los efectos de la aplicació n de esta técnica sobre la producció n de gramíneas y otros atributos de la vegetació n. El objetivo de nuestro estudio fue comparar diferentes atributos de la vegetació n entre á reas roladas y sembradas con pasto buffel y matorrales degradados (testigo). Para ello se seleccionaron ocho á reas roladas y sembradas, y ocho áreas testigo adyacentes. Se evaluó la producció n de gramíneas, la cobertura y densidad de la vegetació n, y el nú mero de especies, diversidad y equitatividad. La producció n de gramíneas, la cobertura de gramíneas perennes totales, y la densidad de gramíneas perennes totales fue mayor (P , 0.05) en las á reas sometidas a rolado y siembra. La mayor producció n de gramíneas en las áreas roladas y sembradas respecto a las testigo, se relacionó positivamente con la cobertura de pasto buffel (r 2 ¼ 0.79). La cobertura de arbustos fue menor (P , 0.05), en á reas roladas y sembradas. Sin embargo, no se detectaron diferencias (P. 0.05) entre áreas en la densidad de arbustos. Tampoco se detectaron diferencias ...
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