Sb. Onofre et al., Pathogenicity of four strains of entomopathogenic fungi against the bovinetick Boophilus microplus, AM J VET RE, 62(9), 2001, pp. 1478-1480
Objective-To evaluate the pathogenicity of 4 strains of the entomopathogeni
c fungi Metarhizium flavoviride var flavoviride and Metarhizium anisopliae
var anisopliae in vitro against the bovine tick Boophilus microplus.
Sample Population-300 B microplus females were used for each series of 5 co
nidial suspensions of the 4 fungal strains; a control group of 60 females w
as treated with sterilized water.
Procedure-For each fungal strain, sporulating cultures were used to produce
conidial suspensions containing 10(4), 10(5), 10(6), 10(7), and 10(8) coni
dia/ml. A bioassay was per-formed by immersing B microplus females in conid
ial suspensions; the procedure was repeated with a new group of 60 females
for each dilution (a total of 300). A control group was immersed in the sam
e volume of sterilized distilled water. Ticks were maintained at 27 C and 8
0% relative humidity for 7 days, and the following variables were evaluated
: weight before egging, egging weight, percentage eclosion, reproductive ef
ficiency, and percentage control.
Results-A low index of eclosion was found in the treated groups, with a pro
gressive decrease in percentage eclosion (control=100%) with increased coni
dial concentration. The highest level of effectiveness of biocontrol was de
tected in groups treated with concentrations of 10(7) and 10(8) conidia/ml.
Conclusions and Clinical Relevance-Strains of the entomopathogenic fungi M
anisopliae var anisopliae and M flavoviride var flavoviride were effective
as biological control agents against B microplus, with M flavoviride strain
CG-291 being the most effective. The pathogenicity of these strains and th
e development of an application method for this fungus for control of ticks
may result in improved animal productivity and a reduction in environmenta
l pollution through the use of fewer chemical insecticides.