Controle de larvas de Boophilus microplus por Metarhizium anisopliae em pastagens infestadas artificialmente

Abstract

Resumo -O objetivo deste trabalho foi avaliar a eficiência do controle exercido por Metarhizium anisopliae na população de Boophilus microplus, em pastagens de Brachiaria brizantha, e do híbrido Tifton 85 (Cynodon spp.), artificialmente infestadas com fêmeas ingurgitadas do carrapato. Control of Boophilus microplus larvae by Metarhizium anisopliae in artificially infested pasturesAbstract -The objective of this work was to evaluate the efficiency of Metarhizium anisopliae fungus against Boophilus microplus population in Brachiaria brizantha and Tifton 85 (Cynodon) pastures, artificially infested with tick engorged females. Thirty plots of 1 m 2 each were randomly distributed in fifteen treated and fifteen control groups per type of grass, establishing five repetitions for each treatment. Pastures were infested with engorged tick females standardized by number and weight. Metarhizium anisopliae suspension with 1.8x10 8 conidia mL -1 concentration was sprayed on the plot in three different assays, prior infested with tick females, immediately after tick inoculation and at first larvae emergency. The fungus action was evaluated at 35 th , 38 th , 41 st , 48 th , 55 th and 61 st day post infestation by counting recovered larvae. A significative reduction of larvae counts occurred in fungus treated groups during 35 th to 48 th day post infestation, ranging between 87% and 94% of efficacy on tick larvae control. The mean values for larvae counting in Tifton 85 pasture were lower than in B. brizantha plot in all analysis, suggesting the pasture effect on fungus action. Treatment strategy influenced on M. anisopliae activity, which demonstrated better results at 41 st and 55 th day post infestation in B. brizantha, submitted to conidia challenge after larvae emergency.

Virulence of Mexican isolates of entomopathogenic fungi (Hypocreales: Clavicipitaceae) upon Rhipicephalus=Boophilus microplus (Acari: Ixodidae) larvae and the efficacy of conidia formulations to reduce larval tick density under field conditions

“…In particular, Citroline was used in combination with other carriers including water, as opposed to the formulae used by Hernández-Velázquez et al (2003) where Citroline was used as the sole component and applied as Ultra Low Volume (ULV). However, there is evidence suggesting that the grass species grown in a pasture bed along with weather conditions also affect the action of M. anisopliae to control R. microplus (Kaaya and Hassan, 2000;Basso et al, 2005).…”

“…M. anisopliae and B. bassiana are known to cause high mortality in various life stages of R. microplus (Bittencourt et al, 1992(Bittencourt et al, , 1994a(Bittencourt et al, ,b, 1996(Bittencourt et al, , 1997aSamish and Rehacek, 1999). However, studies of fungal effects on ticks under field conditions are scarce (Benjamin et al, 2002;Bittencourt et al, 2003;Basso et al, 2005;Alonso-Díaz et al, 2007). In Latin America field tests have been reported showing promising results; in Brazil, Bittencourt et al (2003) found 53.78% reduction of R. microplus larvae after the application of M. anisopliae on pasture beds of Brachiaria decumbens Stapf using a concentration of 10 9 conidia/mL in water suspension.…”

“…In Latin America field tests have been reported showing promising results; in Brazil, Bittencourt et al (2003) found 53.78% reduction of R. microplus larvae after the application of M. anisopliae on pasture beds of Brachiaria decumbens Stapf using a concentration of 10 9 conidia/mL in water suspension. More recently, Basso et al (2005) evaluated the effect of M. anisopliae applied in a water suspension against R. microplus larvae and reported reduction of larvae ranging between 88 and 94.08%.…”

Selection of Filamentous Fungi for the Biocontrol of Rhipicephalus (Boophilus) Microplus in Tropical Regions

“…Ticks are ectoparasites characterized mainly by blood feeding, independently of family, genus or species [1], and the species Rhipicephalus microplus causes substantial losses for beef and milk cattle due to spoliation of cattle and the high cost of current control techniques [2][3][4]. These parasites have a lifecycle in the host and another in the pasture, and only females fill with blood, after they release themselves from the host and fall to the ground, where they seek a dark and humid place, suitable to lay their eggs [5].…”

Evaluation of entomopathogenic fungi as biological control agents Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae)

“…The fungi Metarhizium anisopliae (Metschnikoff, 1879) Sorokin, 1883 (Ascomycota: Nectriaceae) and Beauveria bassiana (Balsamo) Vuillemim, 1912 (Ascomycota: Clavicipitaceae) are promising agents for the biological control of ticks, thus in recent years a number of studies have investigated the relationships between entomopathogenic fungi and different species of tick (Bittencourt et al 1994, Bittencourt et al 1996, Bittencourt et al 1997, Correia et al 1998, Bittencourt et al 1999, Frazzon et al 2000, Bahiense y Bittencourt 2004, Basso et al 2005, Lopes et al 2007, Bahiense 2007.…”