Susceptibility of different populations of ticks to entomopathogenic fungi

Abstract

This study aimed to evaluate the in vitro effect of the entomopathogenic fungi Metarhizium anisopliae sensu lato (s.l.) and Beauveria bassiana sensu lato (s.l.) on two distinct populations of Rhipicephalus microplus, from two different experimental farms. Bioassays were performed with engorged females, eggs and larvae. Fungal infection was evaluated based on biological parameters of treated engorged females, percentage of hatch from treated eggs, and percentage of mortality and mean lethal time (LT90) of treated larvae. When the treatments were compared between the two populations, there were significant differences in the following parameters: pre-oviposition period, hatching period and egg production index. Moreover, the results showed that B. bassiana s.l., isolate Bb 986, was more virulent than M. anisopliae s.l., isolate 959, for engorged females, showing a control percentage of 49%. In the bioassay with eggs, the hatching percentage ranged from 3.1% to 49.5% in one population and from 3.4% to 42.7% in the other, with no significant difference between the two populations. In the bioassay with unfed larvae, the mortality percentage ranged from 91.8% to 98.7% in one population and from 71.0% to 94.0% in the other. The LT(90) varied from 19.52 to 27.51 days in one of the populations and 22.89 to 37.31 days in the other. These results suggest that populations of R. microplus show distinct variation in their susceptibility to B. bassiana s.l. and M. anisopliae s.l.

Effect of heat stress and oil formulation on conidial germination of Metarhizium anisopliae s.s. on tick cuticle and artificial medium

“…Fluorescence microscopy was not possible for conducting experiment 3 because Calcofluor White did not stain conidia covered with oil. Also, differences in conidial germination may occur in ticks from different populations, since ticks from different populations may have different susceptibilities to fungal infection (Fernandes et al, 2011;Perinotto et al, 2012). In the current study, experiments 2 and 3 were conducted on different occasions with ticks from different locations.…”

Inter- and intra-specific variation of spider mite susceptibility to fungal infections: implications for the long-term success of biological control

“…Irigaray et al 2003;Klingen and Westrum 2007;Shi et al 2005). However, these studies were conducted using a single host population and potential intraspecific variations in spider mites susceptibility have, to our knowledge, never been investigated within a single experiment (but see, for instance, Afifi et al 2010;Fiedler and Sosnowska 2007;Ribeiro et al 2009 for a comparison among spider mites and/or among other arthropod species; or Milner 1982;1985;Perinotto et al 2012;Uma Devi et al 2008 for intraspecific variation within other arthropod species).…”

Acaricidal activity of Metarhizium anisopliae isolated from paddocks in the Mexican tropics against two populations of the cattle tick Rhipicephalus microplus

“…Therefore, it is hoped that EF isolated from cattle farms will be effective against tick populations that are either susceptible or multi‐resistant to chemical acaricides. Perinotto et al () observed not only that different populations of ticks can have different levels of susceptibility to biological control using EF and that the genotypic characteristics of the tick are important factors, but also, by contrast, that when a tick population is resistant to chemical acaricides, it is inappropriate to neglect the possible interference of the tick resistance mechanism in the performance of EF. Thus, the objectives of the present study were: (a) to evaluate the acaricidal effects of 55 strains of M. anisopliae isolated from tropical cattle farms in engorged females from two populations of R. microplus , of which one was multi‐resistant and one susceptible to chemical acaricides, and (b) to determine the lethal concentrations required to kill 50% (LC 50 ) and 99% (LC 99 ) of engorged ticks using fungal strains with high acaricidal effects.…”