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

Departamento de Agronomía, División de Ciencias de la Vida, Campus Irapuato-Salamanca, Universidad de Guanajuato, Carretera Irapuato-Silao, Apartado Postal 311, Irapuato, Guanajuato, CP 36500, Mexico.
Veterinary Parasitology (Impact Factor: 2.46). 03/2010; 170(3-4):278-86. DOI: 10.1016/j.vetpar.2010.02.037
Source: PubMed


The first objective was laboratory evaluation of the virulence of 53 Mexican isolates of fungi against larvae of Rhipicephalus (Boophilus) microplus. Thirty-three isolates of Metarhizium anisopliae var. anisopliae (Metschnickoff) Sorokin (Hypocreales: Clavicipitaceae) and 20 isolates of Isaria (Paecilomyces) fumosorosea (fumosoroseus) (Wize) (Eurotiales: Trichomaceae) were tested on 7-day-old larvae under laboratory conditions. Larvae were immersed in a suspension containing 10(8)conidia/mL and the CL(50) values were estimated. Then, field tests were conducted to determine the efficacy of formulations of the isolate with the highest virulence. M. anisopliae (Ma 14 isolate) was formulated with four carriers: Tween, Celite, wheat bran, and Citroline (mineral oil) and applied on pasture beds of Cynodon plectostachyus (L.), at a dose of 2 x 10(9)CFU/m(2). In the first trial, M. anisopliae was applied on plots naturally infested with larvae; in the second trial, tick populations in the experimental plots were eliminated and then re-infested with 20,000 7-day-old larvae. In the laboratory, all M. anisopliae isolates infected larvae with a mortality range between 2 and 100%; also, 13 of 20 I. fumosorosea isolates caused mortality rates between 7 and 94%. In the first field trial, 14 days post-application, conidial formulations in Celite and wheat bran caused 67.8 and 94.2% population reduction, respectively. In the second trial, the Tween formulation caused the highest larval reduction, reaching up to 61% (28 days post-application). Wheat bran formulation caused 58.3% larval reduction (21 days post-application) and was one of the most effective. The carriers and emulsifiers have a large impact on the effectiveness of conidial formulations.

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Available from: Alfonso Pescador-Rubio
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    • "M. anisopliae effects on R. microplus ticks have been evaluated in several in vitro studies with promising results (Bittencourt et al., 1992; Frazzon et al., 2000; Costa et al., 2001; Onofre et al., 2001; Fernandes et al., 2004; Arruda et al., 2005; Polar et al., 2005b; Bahiense et al., 2006; Leemon and Jonsson, 2008; Perinotto et al., 2014). However , its efficacy in pen trials (Correia et al., 1998; Bahiense et al., 2007; Leemon et al., 2008; Ángel-Sahagún et al., 2010) and direct application on pasture (Garcia et al., 2011) do not appear to have significant effects on tick control. Some promising results were reached under field conditions (Kaaya and Hassan, 2000; Polar et al., 2005a; Basso et al., 2005; Alonso-Díaz et al., 2007; López et al., 2009; Ojeda-Chi et al., 2010) and demonstrated the need for further studies with this model. "
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    ABSTRACT: The efficacy of the fungus Metarhizium anisopliae to control ticks has been shown in several in vitro experiments. However, few studies have been undertaken in field conditions in order to demonstrate the applicability of its use as a biological control of ticks and its combination with chemical acaricides. The aim of the present study was to evaluate the efficacy of M. anisopliae to control an acaricide-resistant strain of Rhipicephalus microplus under laboratory and field conditions. First, the compatibility of M. anisopliae strain (TIS-BR03) with commercial acaricides and its potential to control the cattle tick were evaluated in vitro. In general, acaricide treatments had mild effects on fungus viability. In the field experiment, the median of treatment efficacy with acaricide only, M. anisopliae only and combination of M. anisopliae with acaricide were 71.1%, 56.3% and 97.9%, respectively. There is no statistical difference between groups treated with M. anisopliae and acaricide alone. Thus, in this work we have demonstrated the applicability of M. anisopliae use associated or not with chemical acaricides on field conditions in order to control an acaricide-resistant strain of the cattle tick R. microplus.
    Full-text · Article · Jan 2015 · Veterinary Parasitology
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    • "Several reports have shown improved tick control by M. anisopliae conidia in a formulation with some particular oil (Kaaya and Hassan, 2000; Maranga et al., 2005; Leemon and Jonsson, 2008; Ángel-Sahagún et al., 2010; Camargo et al., 2012). However, only a few studies have compared the effects of different types of oils on the performance of these conidia against ticks (Polar et al., 2005). "
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    ABSTRACT: High infectivity of entomopathogenic fungi to ticks under laboratory conditions has been demonstrated in many studies. However, the few reports on their use under field conditions demonstrate large variations in their success, often with no clear explanation. The present study evaluated the factors affecting the efficacy of the fungus Metarhizium brunneum against the tick Rhipicephalus (Boophilus) annulatus. It demonstrates how environmental conditions and ground cover affect the efficiency of the fungus under field conditions. During the summer, 93% of tick females exposed to fungus-contaminated ground died within 1 week, whereas during the winter, only 62.2% died within 6 weeks. Nevertheless, the hatchability of their eggs was only 6.1% during the summer and 0.0% during winter. Covering the ground with grass, leaves or gravel improved fungal performance. Aside from killing female ticks, the fungus had a substantial effect on tick fecundity. Fungal infection reduced the proportion of female ticks laying full-size egg masses by up to 91%, and reduced egg hatchability by up to 100%. To reduce the negative effect of outdoor factors on fungal activity, its conidia were mixed with different oils (olive, canola, mineral or paraffin at 10% v/v) and evaluated in both laboratory and field tests for efficacy. All tested oils without conidia sprayed on the sand did not influence tick survival or weight of the laid eggs but significantly reduced egghatchability. Conidia in water with canola or mineral oil spread on agarose and incubated for 18 h showed 57% and 0% germination, respectively. Comparing, under laboratory conditions, the effects of adding each of the four oils to conidia in water on ticks demonstrated no effect on female mortality or weight of the laid egg mass, but the percentage of hatched eggs was reduced. In outdoor trials, female ticks placed on the ground sprayed with conidia in water yielded an average of 175 larvae per female and there was no hatching of eggs laid by females placed on ground sprayed with conidia in water with canola or mineral oils.
    Full-text · Article · Nov 2014 · Veterinary Parasitology
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    • "Among acaripathogenic fungi, Beauveria and Metarhizium have been the most studied genera for tick control (Fernandes et al., 2012). Several studies have demonstrated the importance of using these fungi in a formulation, not just suspended in water, for controlling ticks (Kaaya, 2000; Kaaya and Hassan, 2000; Maranga et al., 2005; Polar et al., 2005; Alonso-Díaz et al., 2007; Leemon and Jonsson, 2008; Leemon et al., 2008; Souza et al., 2009; Ángel-Sahagúna et al., 2010; Kaaya et al., 2011). Some of these studies evaluated the fungal formulations against ticks through in vivo tests; however, more studies are required to obtain formulations that maintain the viability and efficacy of acaripathogenic fungi for tick control in the field. "
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    ABSTRACT: The present study evaluated, for the first time, the effect of the commercial formulation Metarril® SP Organic of Metarhizium anisopliae plus 10% mineral oil to control Rhipicephalus microplus in a pen study. Three groups were formed with six animals each: the first group was exposed to Metarril® plus 10% mineral oil and 1% Tween 80; the second group was exposed to sterile distilled water, mineral oil and Tween 80 (oil control group); and the third group received no treatment (control group). The fungal formulation contained 1 × 108 conidia ml−1. Each animal was sprayed with 3 L of formulation. Fallen ticks were counted daily and a sample of 20 engorged females per day was incubated for assessment of biological parameters. Throughout the study period, Metarril® oil-based formulation showed an efficacy ranging from 19.20% to 67.39% in comparison with the control group; and from 8.18% to 61.38% in comparison with the oil control group. The average efficacy of Metarril® oil-based formulation was 47.74% and 40.89% in comparison with control and oil control groups, respectively. Changes in the biological parameters of engorged R. microplus females were observed in the first three days after treatment, with a significant reduction in hatching percentage and egg production index. We concluded that Metarril® SP Organic plus 10% mineral oil was efficient against R. microplus in pen studies. However, further in vivo studies are required to increase the efficacy and to establish a protocol for the use of this product in the field against the cattle tick.
    Full-text · Article · Sep 2014 · Veterinary Parasitology
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