In vitro assessment of Metarhizium anisopliae isolates to control the cattle tick Boophilus microplus

Metarhizium anisopliae is a filamentous fungus used for tick control. The i n vitro effects of 12 M, anisopliae isolates on engorged Boophilus microplu s females were analysed. The most pathogenic isolate (E6S1) caused a 100% d eath rate when 10(7) spores/mi were used to infect ticks. Isolates of M, an isopliae taken from experimentally infected ticks proved to be more pathoge nic than fungus maintained on culture media. A comparison between dsRNA myc ovirus-free and infected M, anisopliae isolates suggested that, in general, virus free isolates were more infective. The results showed that the biolo gical control of B. microplus by M, anisopliae infection might constitute a n additional method to integrated tick control management, (C) 2000 Elsevie r Science B.V. All rights reserved.