The lone star tick Amblyomma americanum L. is the most abundant tick in Arkansas and has been implicated as a vector of many important disease-causing pathogens. Many species of entomopathogenic fungi have been isolated from several species of ticks, with some of these fungi being utilized for tick biocontrol. However, few studies have assessed the pathogenicity of entomopathogenic fungi to A. americanum. The objectives of this study were to: isolate and identify native Arkansas isolates of entomopathogenic fungi from wild A. americanum ticks exposed to soil and to compare the pathogenicity of one isolate (Metarhizium anisopliae (Metchnikoff) Sorokin isolate Savoy P10N1) to that of the mycoinsecticide Met52® (M. brunneum Petch strain F52) on adult, nymphal and larval A. americanum. Ticks exposed to soil from Savoy, Arkansas were infected with M. anisopliae with infection percentages of 3.3% (N = 60), 1.6% (N = 60) and 1.5% (N = 200) for adult females, adult males and nymphal ticks respectively. Only nymphal ticks exposed to soil from West Fork, Arkansas (2.4% of nymphs; N = 210) were infected with M. anisopliae. Eight isolates of M. anisopliae were cultured from infected A. americanum ticks. Two of these isolates (Savoy P10N1 and West Fork P9N2) were confirmed as M. anisopliae by genetic sequencing and a GenBank Blast analysis. Adults and nymphs were more susceptible to Met52® than to Savoy P10N1. Adults treated with Met52® died at twice the rate as adults treated with Savoy P10N1. Nymphs treated with Met52® died at the same rate as nymphs treated with Savoy P10N1 after 88.4±6.8% of nymphs died at two days post-inoculation (days PI). Adult mortality for Met52® was 25.3±8.3% and 100% at 14 and 77 days PI respectively compared to <1% and 25.4±8.7% for Savoy P10N1. Nymphal mortality for Met52® at 14 and 77 days PI was 89.8±6.0% and 100% while mortality for Savoy P10N1 was 5.3±3.3% and 33.1±14.4%. Assessments on larval mortalities for all treatments were inconclusive due to unknown variables. Findings from this study will give a better understanding of the entomopathogenic fungi to be evaluated for the control of A. americanum in future studies.
|Commitee:||Steinkraus, Donald, Szalanski, Allen|
|School:||University of Arkansas|
|School Location:||United States -- Arkansas|
|Source:||MAI 81/11(E), Masters Abstracts International|
|Keywords:||Bioassay, Biocontrol, Entomopathogenic fungi, Isolation, Ticks|
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