Extrato alcoólico de capim-cidreira (Cymbopogon citratus) no controle do carrapato (Boophilus microplus) de bovinos leiteiros

Abstract

The work was conducted in Santa Maria (RS), with the objective of to evaluate the effectiveness of the lemongrass (Cymbopogon citratus) in the control of Boophilus microplus (Canestrini, 1887) tick, compared to a synthetic acaricide. The trials were developed in the Dairy Cattle and in the Parasitic Diseases of the Domestic Animals Laboratories of the Federal University of Santa Maria, from May to December, 2003. In vivo and in vitro trials were conducted. Twelve Holstein cows were distributed in three groups of four animals each. A group was treated with amitraz. The others were treated with basic formulations of lemongrass extracts (technical recommendation for use in field level), corresponding from 1.36 and 2.72% of plant. An experimental design was constituted entirely randomized with three treatments and four repetitions each. For evaluation, they were counted engorged female ticks, up 4.0 mm length, before and after the application of the products (1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 14th day). Amitraz treatment presented, in the 3rd, 7th and 14th day after the application, 100, 99.5 and 94.4% of effectiveness against engorged female ticks, respectively. Only the product contends 2.72% of lemongrass presented a partial control of ticks of 40.4; 46.6 and 41% in the 3rd, 7th and 14th day, after application, respectively. In in vitro experimentation, was studied the effectiveness of different products obtained by maceration of lemongrass plants, in comparison at the amitraz, on the ovipositional and eggs viability of engorged female ticks. For evaluation, method of the adult immersion test was used. The treatments were constituted by products contends 1.36% of macerated plant (technical recommendation), pure extracts (without water dilution) obtained of 150, 300, 600 and 1200g of macerated for liter of ethilc alcohol, forming products contends 13.04; 23.08; 37.50 and 54.55% of plant, respectively, and for amitraz at 0.025%. The engorged female ticks was divided by size and engorge level in light (between 4.5 and 7 mm length) and heavy (larger of 7 mm), being 10 heavy and 10 light submitted to one, two or three immersions in each tested products. The experimental design was it entirely randomized in an outline factorial (tested products X randomized number of immersions X engorged level). Amitraz presented effectiveness of 99.98% in the reduction of the ovipositional and egg viability. The tested products presented mean effectiveness of 28.50%, 54.28% and 71.05% when applied one, two and three times (immersions), respectively. The increase in the number of immersions of one for three increased in 42.55% the effectiveness of the products. The mean effectiveness of the products tested on the engorged female ticks light (53.22%) was better in relation to the heavy ones (49.24%). The tested products with 13.04; 23.08 and 37.5% of lemongrass presented effectiveness of 52.22; 55.31 and 52.60% of effectiveness, respectively, demonstrating similar behavior. Effectiveness up 90% was obtained in three immersions for products contends 23.08% and 37.50% applied on light (92.05%) and heavy (92.62%) engorged female ticks, respectively. The product contends lemongrass macerated plant at 1.36% presented the smallest effectiveness, with 8.18%.