Field evaluation of Beauveria bassiana (Balsamo) Vuillemin isolates for the biocontrol of Rhipicephalus microplus (Canestrini) ticks on cattle

Formulations of the entomopathogenic fungus Beauveria bassiana (Hypocreales: Cordycipitaceae) were tested under field conditions against the bovine tick adults Rhipicephalus microplus (Acari: Ixodidae). Formulations were prepared for each fungal isolate consisting of 10(8) conidia.mL(-1), 10% avocado oil and either of Ballista (R) or Break-thru (R) as an adjuvant sprayed on tick-infested cows. The following variables were evaluated: initial female weight, egg mass, hatching percentage, egg production index, nutritional index, reproductive efficiency and mortality. After about four days, the ticks were collected to estimate all the variables mentioned above. Mortality for treated ticks ranged from 13 to 38%. All isolate formulations significantly reduced egg mass, hatching percentage of the eggs, egg production index, nutritional index and reproductive efficiency. The current study demonstrated the potential of B. bassiana formulations for the biological control of R. microplus under environmental field conditions.