ABSTRACT
This study was carried out with the objective of evaluating the efficacy of a 2,6-dichlorophenol (2,6-DCP) lure to control Dermacentor nitens (Acari: Ixodidae). Slow-release formulations of the pheromone formulated with and without cypermethrin were prepared. Olfactometer bioassays were used to define the best dose of the pheromone and to evaluate the effect of cypermethrin with 2,6-DCP attractiveness. Sexually active males were released 15 cm from 2 cmx1 cm pieces of polypropylene treated with different odors: 2,6-DCP in a liposphere system (1.5, 30 and 300 microg--without cypermethrin and 30 microg--with cypermethrin) and 2,6-DCP in hexane (30 microg). The tests were conducted 7 and 15 days after the preparation of the odor sources. The percentages of males that oriented, or showed directional movement toward the stimulus, and their tracks were recorded. Lures (10 cmx2 cm pieces of polypropylene) treated with the best dose of the liposphere formulation (30 microg) were prepared. The lures were evaluated in horses that had been artificially infested with D. nitens. The horses' ears were infested with 3000 D. nitens larvae per ear, once weekly for 4 weeks. The animals were divided into three groups: control, 2,6-DCP and 2,6-DCP+cypermethrin. On day 0, the lures of their respective treatments were attached to the horses' napes. From days 6 to 20 after attachment, female ticks of 4 mm or over in length were counted on the ears, every 2 or 3 days. Olfactometer analysis showed higher orientation to 30 microg dose and more prolonged release of the pheromone in the liposphere formulation than in hexane; cypermethrin did not interfere with the attractive effect of the pheromone. The lures were efficient in the first 10 days after attachment, when the mean number of females was higher in the control group (24.9) than in 2,6-DCP and cypermethrin (5.4), and 2,6-DCP (9.2) groups. After that period the number of females was similar in the control and treated groups. These results indicate that 2,6-DCP lures used in a liposphere formulation can control D. nitens for at least 10 days by preventing its copulation. However, further evaluation of longer-term pheromone release under natural conditions is needed in order to validate this kind of control. In addition, the use of extra lures on the horse's tail may help to control populations on the hindquarters.
Subject(s)
Chlorophenols/pharmacology , Dermacentor , Horse Diseases/prevention & control , Tick Control/methods , Tick Control/standards , Tick Infestations/veterinary , Animals , Female , Horse Diseases/parasitology , Horses , Insecticides , Male , Pheromones/pharmacology , Pyrethrins , Tick Infestations/prevention & control , Time FactorsABSTRACT
A eficácia de um extrato hexânico dos frutos de Melia azedarach foi avaliada em bezerros infestados artificialmente com Boophilus microplus. Os frutos foram submetidos ao processo de secagem e, depois de moídos, o extrato foi produzido em Soxhlet utilizando-se o hexano como extrator. Oito bezerros infestados artificialmente, cinco vezes a cada cinco dias com 2.500 larvas de B. microplus, foram divididos em dois grupos (tratado e controle) com base na infestação por carrapatos. No dia zero os animais foram banhados com 3 litros de uma solução a 0,25por cento do extrato em água e acetona (1,2 litro). Os animais do grupo controle foram banhados com o mesmo volume de água e acetona. Diariamente, as fêmeas ingurgitadas desprendidas naturalmente eram contadas e 40 eram incubadas para acompanhamento dos parâmetros reprodutivos. O número médio de fêmeas, o índice de conversão em ovos (peso da massa de ovos/ peso do grupo de fêmeas x 100) e o percentual de eclosão, obtidos nos dois grupos, foram comparados mediante o teste T de Student. Após 21 dias de contagens, o número médio de fêmeas ingurgitadas foi significativamente menor (P<0,05) no grupo tratado (188) do que no controle (247). Porém, a conversão e a eclodibilidade das larvas não foram afetadas pelo tratamento. Estes resultados indicam que houve interferência da planta no desenvolvimento do carrapato sobre os animais, mas não na sua reprodução. Comparados com a literatura, os resultados se revelaram promissores. No entanto, novos estudos nos quais se empregue uma formulação adequada em uma concentração mais elevada são necessários para se propor o uso desta planta no controle deste carrapato.
