Abstract
Ticks and tick-borne diseases represent a major constraint to cattle production in Kenya. The use of entomopathogenic fungi is an important and promising component of bio-control agents for controlling devastating tick species which include Rhipicephalus appendiculatus, Amblyomma variegatum and Rhipicephalus (Boophilus) decoloratus. The aim of this study was to evaluate the efficacies of the fungus Metarhizium anisopliae ICIPE 7 and the acaricide, amitraz in controlling R. decoloratus in naturally infested cattle under field conditions.
This study was undertaken during the short rains (October to November 2014) in Narok County, Kenya. Twenty animals (steers and heifers) were randomly allocated to four treatment groups; Control (water + 0.05% Triton X–100 + 15% canola oil); M. anisopliae ICIPE 7 isolate alone (1×109 conidia ml-1); Amitraz alone at recommended concentration of 0.2% and combination of M. anisopliae ICIPE 7 isolate (1 x 108 conidia ml-1) and amitraz (0.1%).
The overall R. decoloratus load was high at the start of treatment (day 0) in all the four groups and was highest along the dewlap followed by the back region while the head region had no blue ticks. All the three treatments reduced tick counts significantly on days 7, 14, 21 and 28 relative to the control group with percentage efficacy on day 28 post treatment being 69.2% for ICIPE 7, 67.1% for ICIPE 7 plus amitraz and 94.9% for amitraz alone. Treatments with M. anisopliae ICIPE 7 alone and M. anisopliae ICIPE 7 isolate plus amitraz attained mortality of 93.5% compared to 2.3% of the control group and all fungal infected ticks developed mycosis. This study has demonstrated that M. anisopliae ICIPE 7 isolate was as effective as amitraz and when combined as a spray reduced the tick population significantly. This association could be used as a tool for integrated control of R. decoloratus.

Key words: acaricide, anaplasmosis, Babesia bigemina, conidia, entomopathogenic fungi, tick resistance.