John Furlong

Efeito acaricida de óleos essenciais e concentrados emulsionáveis de Eucalyptus spp em Boophilus microplus

Realizou-se um estudo sobre a acao biocida de Eucalyptus citriodora, Eucalyptus globulus e Eucalyptus staigeriana no carrapato Boophilus microplus, buscando-se a producao de acaricidas menos agressivos ao meio ambiente. Os oleos essenciais das tres especies e os concentrados emulsionaveis de E. globulus e E. staigeriana foram testados em cinco concentracoes diferentes contra larvas e femeas ingurgitadas de B. microplus. Os oleos foram submetidos a analise por cromatografia gasosa acoplada a espectrometria de massas (CG/EM), a fim de se investigar sua composicao. O citronelal e o principal componente do oleo de E. citriodora, sendo responsavel por sua acao acaricida. O mesmo ocorre com o 1,8-cineol em E. globulus. Em E. staigeriana existem varias substâncias que agem sinergicamente contra B. microplus. O oleo essencial de E. citriodora matou 100% dos carrapatos a uma concentracao media de 17,5%, o de E. globulus a 15% e o de E. staigeriana a 12,5%. Os concentrados emulsionaveis de E. globulus mataram 100% dos carrapatos a uma concentracao media de 9,9% e o de E. staigeriana a uma concentracao de 3,9%. O desenvolvimento de produtos que possam ser testados a campo e comercializados a precos competitivos serao passos a serem seguidos. Os biocarrapaticidas tem um apelo comercial grande, permitindo controlar B. microplus de um modo menos agressivo ao meio ambiente.

Percepção dos produtores de leite do município de Passos, MG, sobre o carrapato Boophilus microplus (Acari: Ixodidae), 2001

Twenty five dairy farms were randomly chosen from all farms producing more than 500 liters of milk/ day in Passos, MG, Brazil. The owners were interviewed to characterize their perceptions about the biology of B. microplus and their attitudes towards tick control. Most of the producers have a college degree and more than six year-experience in the activity. The biological damages caused by ticks are perceived by the farmers. Their tick control is performed without technical criteria and they did not show a proper knowledge on the biology of B. microplus nor on the toxicological risks of acaricides application. The results reveal a gap between the technology and farmers, favoring tick resistance to acaricides.

Genome wide scan for quantitative trait loci affecting tick resistance in cattle (Bos taurus × Bos indicus).

BackgroundIn tropical countries, losses caused by bovine tick Rhipicephalus (Boophilus) microplus infestation have a tremendous economic impact on cattle production systems. Genetic variation between Bos taurus and Bos indicus to tick resistance and molecular biology tools might allow for the identification of molecular markers linked to resistance traits that could be used as an auxiliary tool in selection programs. The objective of this work was to identify QTL associated with tick resistance/susceptibility in a bovine F2 population derived from the Gyr (Bos indicus) × Holstein (Bos taurus) cross.ResultsThrough a whole genome scan with microsatellite markers, we were able to map six genomic regions associated with bovine tick resistance. For most QTL, we have found that depending on the tick evaluation season (dry and rainy) different sets of genes could be involved in the resistance mechanism. We identified dry season specific QTL on BTA 2 and 10, rainy season specific QTL on BTA 5, 11 and 27. We also found a highly significant genome wide QTL for both dry and rainy seasons in the central region of BTA 23.ConclusionsThe experimental F2 population derived from Gyr × Holstein cross successfully allowed the identification of six highly significant QTL associated with tick resistance in cattle. QTL located on BTA 23 might be related with the bovine histocompatibility complex. Further investigation of these QTL will help to isolate candidate genes involved with tick resistance in cattle.

Steinernema glaseri Santa Rosa strain (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora CCA Strain (Rhabditida: Heterorhabditidae) as biological control agents of Boophilus microplus (Acari: Ixodidae).

The present study was carried out to evaluate the action of Steinernema glaseri Santa Rosa strain and Heterorhabditis bacteriophora CCA strain as biological control agents of Boophilus microplus. Engorged females ticks were distributed on Petri dishes containing different concentrations of infective juvenile (IJ) nematodes (0, 375, 500, 750, 1,500, 2,500, 5,000 and 25,000). The data showed a reduction of approximately 90% in the eggs laid at a concentration of 5,000 S. glaseri IJs and approximately 80% at a concentration of 1,500 H. bacteriophora IJs. The female mortality increased linearly with the increase in S. glaseri concentrations. However, in the tests with H. bacteriophora this linearity was not observed. The effectiveness of the treatment with both species of entomopathogenic nematodes was compatible with other control methods. The results show the potential of S. glaseri and H. bacteriophora as biological control agents for the control of B. microplus under laboratory conditions.

Controle do carrapato Boophilus microplus (Acari: Ixodidae) em sistemas de produção de leite da microrregião fisiográfica fluminense do grande Rio - Rio de Janeiro

The objective of the study was to analyse the control methods of the cattle tick, Boophilus microplus. The experiment was carried out on three farms of the dairy production systems of the Fluminense Physiographic Microregion of Grande Rio, Rio de Janeiro State, Brazil. Farm management, the Bos indicus and Bos taurus composition of herds, climatic factors and seasonal variation in tick infestation level of cattle was taken into account. Counts of engorged female ticks, measuring between 4.5 and 8.0mm, in 20% of the lactating cows of each farm, were carried out during one year, June 1996 to May, 1997. Pasture management differences, genetic composition of the herds and climatic conditions, influenced the seasonal incidence of B. microplus. The highest cattle stocking rate per hectare, taller vegetative stand of pasture and greater proportion of B. taurus genes in herds contributed to increase tick infestation on farms. The direct control of B. microplus, carried out by the owners on farms, had a secondary importance compared to other factors of herd management. Excessive and inefficient use of chemical acaricide products was observed. Efforts should be made for the transfer and adoption of research results for rural producers to facilitate the implantation of strategic control measures against B. microplus.O objetivo do trabalho foi analisar os métodos de controle do carrapato Boophilus microplus realizados em três fazendas representativas dos sistemas de produção de leite da Microrregião Fisiográfica Fluminense do Grande Rio, Rio de Janeiro, levando-se em consideração o manejo das fazendas, o grau de sangue Bos taurus e Bos indicus dos rebanhos, os fatores climáticos e a prevalência estacional do carrapato. Para efeito de avaliação, foi utiliz ada a contagem periódica de fêmeas ingurgitadas medindo entre 4,5 e 8mm, no antímero direito de 20% das vacas em lactação de cada fazenda, durante um ano. A diferença no manejo das pastagens, a composição genética dos rebanhos e as condições climáticas influenciaram a prevalência estacional de B. microplus. A maior lotação animal por hectare, o elevado “stand” vegetativo das pastagens e o maior grau de sangue B. taurus contribuíram para as maiores infestações de carrapatos nas fazendas. O controle de B. microplus realizado pelos proprietários teve importância secundária em relação as outras atitudes de manejo dos rebanhos. Ficou evidenciado o uso excessivo e ineficiente de produtos químicos para o controle de B. microplus nas fazendas. Para implantação de medidas de controle estratégico do B. Microplus, fazem-se necessários esforços para a transferência e adoção dos resultados de pesquisas disponíveis aos produtores rurais.

A new approach to characterization of the resistance of populations of Rhipicephalus microplus (Acari: Ixodidae) to organophosphate and pyrethroid in the state of Minas Gerais, Brazil

The monitoring of resistance of cattle tick populations in Brazil to the chemical bases in use is largely limited to investigation of the phenotypic profile. There are few studies investigating the role played by the genotypic profile in acaricide resistance in the country. Therefore, the aim of the present study was to carry out molecular characterization and trace out the genetic profile of populations of Rhipicephalus microplus with respect to resistance to the organophosphate and pyrethroid chemical groups. For that purpose, larvae were genotyped belonging to 587 populations for pyrethroids and 306 for organophosphates, using the polymerase chain reaction technique. It was found that 75.49% and 97.44% of the larvae studied showed resistance to the organophosphates and pyrethroids, respectively. Among the populations resistant to pyrethroids, 91.9% were heterozygotes, showing that most of the resistant populations have only one allele responsible for resistance. Therefore, it is possible to conclude that the genotyped populations have high resistance to organophosphates, and even more so to pyrethroids. This information is fundamental for understanding the mechanisms of resistance of R. microplus to acaricides, to enable improvement of control techniques.

Compatibility between the entomopathogenic nematode Steinernema glaseri (Rhabditida: Steinernematidae) and an acaricide in the control of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

There have been studies of the compatibility between entomopathogenic nematodes and insecticides commonly used to control crop pests, but this same approach has not been widely studied regarding the control of ticks. Therefore, this work examines the association between a species of entomopathogenic nematode, Steinernema glaseri, and an organophosphate acaricide to control the cattle tick Rhipicephalus microplus. Engorged females were separated into 12 groups, with ten repetitions each, immersed for 5 min in varied concentrations of acaricide (commercial dose and one-half, one-fourth, one-eighth and one-sixteenth of that dose), associated or not with the nematodes, maintained under controlled conditions. There were two control groups, one containing nematodes and water and the other only water. The absence of egg laying and significant reduction in the survival period of the females in the nematode treatments associated with the lowest acaricide doses demonstrated the compatibility between the two agents. We observed the presence of S. glaseri adults on the cuticle of the females in the treatments with one-eighth and one-sixteenth the commercial dose. These results indicate greater efficacy of the treatments with lower acaricide concentrations in association with S. glaseri, with less environmental impact, reduced costs and less resistance selection pressure on the tick populations.

Potential synergistic effect of Melia azedarach fruit extract and Beauveria bassiana in the control of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in cattle infestations

The use of a concentrate emulsion of Melia azedarach green fruits and a suspension of the fungus Beauveria bassiana was evaluated in the control of Rhipicephalus microplus on artificially infested cattle. The evaluation was conducted following the protocol established by the Brazilian Agriculture Ministry. Five groups of 4 or 5 animals were allocated to one of the following treatments: emulsion concentrate of M. azedarach at 0.25% (T AZED 0.25%), emulsion concentrate of M. azedarach at 0.5% (T AZED 0.5%), B. bassiana at 2.4 × 10(8) conidia (T BASS), association of the concentrate of M. azedarach at 0.25% with B. bassiana at 2.4 × 10(8) conidia (T AZED 0.25%+BASS), and control (untreated). The association of the two compounds provided better results than any one isolated treatment, indicating compatibility or perhaps a synergy between M. azedarach and B. bassiana. This treatment resulted in fewer engorged females (129 ± 70) than in the control group (233 ± 82), showing high performance against all developmental stages of the tick. Results revealed an apparent synergistic effect of M. azedarach and B. bassiana in the control of R. microplus that should be further investigated.

Heterorhabditis amazonensis (Rhabditidae: Heterorhabditidae), strain RSC-5, for biological control of the cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

The aim of this study was to evaluate the influence of different doses of Heterorhabditis amazonensis RSC-5 on the biological parameters of engorged females of Rhipicephalus (Boophilus) microplus. The female ticks, individually identified, were divided into six groups of 20 each and exposed to the following nematode concentrations: 0, 75, 150, 300, 600, and 1,200/female. The following parameters were observed: initial weight, final weight, alteration weight, egg mass weight, pre-oviposition period, oviposition period, survival period, incubation period, hatching percentage, reproductive efficiency index (REI), nutritional efficiency index (NI), and percentage of control. There were no significant differences observed for the initial weight, pre-oviposition period, incubation period, and NI (p > 0.05) between the various treated groups and the control group. However, there were significant differences (p < 0.01) for the oviposition and survival periods between all the treated groups and the control group. For the final weight, alteration weight, egg mass weight, and REI, only the treatment with 1,200 nematode/female did not differ significantly from the respective figures for the control group (p > 0.05). The highest control rate was 67.8%, obtained in the treatment with a concentration of 300 entomopathogenic nematodes/female. The results demonstrate that this nematode has a deleterious effect on the majority of the biological parameters analyzed.

Perceptions about the biology of Rhipicephalus (Boophilus) microplus among milk producers in Divinópolis, Minas Gerais.

One hundred semi-systematized interviews were applied with the aim of surveying the perceptions of milk producers in the municipality of Divinópolis, Minas Gerais regarding the biology of the tick Rhipicephalus (Boophilus) microplus. Content analysis was conducted on each of the variables surveyed and their descriptions, highlighting the higher frequencies in order to construct profiles of perceptions about each of the matters surveyed. In addition, each of the producers was categorized regarding their readiness to proceed with efficient control, from the assessment of their responses. Among the variables surveyed were the tick lifespan, duration of parasitic life, time of greatest incidence, survival in pastures and egg-laying volume. These questions are considered important for defining the knowledge needed for rational combat. It was concluded that the information needed for adopting effective practices to combat ticks was insufficient among the milk farm properties in Divinópolis. Moreover, the producers interviewed had a good perception of what they observed in their daily routine, but did not have complementary information about the tick life cycle.