SeleÇão de isolados do fungo entomopatogênico Beauveria bassiana (Ascomycetes: Clavicipitaceae) para o controle de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Abstract

Seleção de isolados do fungo entomopatogênico (IBCB03, IBCB14, IBCB16, IBCB24, IBCB95, IBCB97, IBCB102, IBCB141, IBCB146, IBCB147, IBCB150, IBCB154, IBCB157), indicaram percentuais de eficiência entre 80 e 89,5%; seis (IBCB47, IBCB75, IBCB84, IBCB145, IBCB161, IBCB164), entre 70 e 79% e apenas dois, (IBCB13 e IBCB143) revelaram-se pouco virulentos com porcentagens abaixo de 70%. Na segunda etapa do trabalho, foram analisados comparativamente dados de mortalidade acumulada dos cinco melhores isolados obtidos na primeira fase (IBCB01, IBCB07, IBCB21, IBCB66, IBCB165). Analisando-se os resultados obtidos in vitro, pode-se imputar que os isolados IBCB21 e IBCB66 são os que apresentam maior potencial para utilização a campo, tendo em vista o controle de R. (B.) microplus. Os isolados selecionados, na primeira fase, também foram testados quanto à potencialidade de produção massal em meio de arroz pré-cozido. A melhor produção massal foi obtida com o isolado IBCB66.Palavras-chave: Carrapato, controle biológico, bovinos. AbstractThis study was carried out to select isolates of the entomopathogenic fungus Beauveria bassiana with pathogenic potential to control the Rhipicephalus (Boophilus) microplus tick. The effectiveness of thirty isolates was first tested at a concentration of 5 × 10 8 conidia.mL -1. Of these, eight were evaluated (IBCB01, IBCB02, IBCB07, IBCB17, IBCB21, IBCB74, IBCB149, IBCB165) and showed an effectiveness between 90 and 99%; thirteen (IBCB03, IBCB14, IBCB16, IBCB24, IBCB95, IBCB97, IBCB102, IBCB141, IBCB146, IBCB147, IBCB150, IBCB154, IBCB157) between 80 and 89,5%; six (IBCB47, IBCB75, IBCB84, IBCB145, IBCB161, IBCB164) between 70 and 79%, and only two (IBCB13 and IBCB143) had lower pathogenicity (70% or below). In the second step of the study, the five more effective strains in the first phase of the experiment (IBCB01, IBCB07, IBCB21, IBCB66, IBCB165) were analyzed comparatively. Based on in vitro results, it can be concluded that IBCB66 and IBCB21 are the isolates with higher potential for field control of R. (B.) microplus. IBCB01, IBCB07, IBCB21, IBCB66 e IBCB165 isolates were submitted to a conidial production test using a rice-based substrate. The best mass production of the entomopathogenic fungus was obtained with the IBCB66 strain.

An intensive search for promising fungal biological control agents of ticks, particularly Rhipicephalus microplus

“…In the present study, however, several B. bassiana isolates obtained from naturally infected ticks (viz., Bb 13, Bb 23, Bb 27, Bb 35) were not significantly more virulent to R. microplus larvae than isolates obtained from other arthropod orders, such as CG 464 or CG 206 isolated from Coleoptera and Hymenoptera, respectively. Also, variation in virulence among entomopathogenic fungal isolates has been reported in several studies with no apparent correlation to other traits (Barci et al, 2009;Luz et al, 1998;Paião et al, 2001;Posadas and Lecuona, 2009).…”

“…Previous studies have obtained high mortality of R. microplus larva at day 10 after treatment with B. bassiana or M. anisopliae s.l. conidia; most of these studies used larvae obtained from engorged females from artificially infested calves (Barci et al, 2009;Bittencourt et al, 1994Bittencourt et al, , 1996Fernandes et al, 2003;Leemon and Jonsson, 2008;Paião et al, 2001;Posadas and Lecuona, 2009). These studies concluded that the variations in tick mortality were directly related to the isolates' differences in virulence.…”

IN VITRO TOXICITY OF CYPERMETHRIN AND DELTAMETHRIN ON THE CATTLE TICK Rhipicephalus microplus

“…In order to evaluate the loss of motility on contact with acaricidal therapeutic compounds, the in vitro method with Pasteur pipette, recommended by Barci and Nogueira (2006), was conducted. Larvae were removed from the better hatchability (> 90%) compared to commercial products described above.…”

Cálculo da CI50 (concentração inibitória média) e CL50 (concentração letal média) do óleo da semente de andiroba (Carapa guianensis, Aubl.) sobre Rhipicephalus (Boophilus) microplus (Canestrini, 1887), Anocentor nitens (Neumann, 1897) e Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

“…Dentre as espécies de ixodídeos, o Rhipicephalus (Boophilus) microplus (Canestrini, 1887) é considerado um dos principais ectoparasitas que acometem bovinos, em virtude dos prejuízos que causa à pecuária brasileira (Barci et al, 2009). Seu parasitismo é responsável por perdas econômicas estimadas em cerca de dois milhões de dólares anuais, valores resultantes com gastos com acaricidas químicos, diminuição do ganho de peso, diminuição da produção do leite e depreciação do couro (Grisi et al, 2002).…”