Selection of Promising Entomo-Pathogenic Fungal Isolates Against Rhipicephalus (Boophilus)

Selection of promising Entomo-pathogenic fungal isolates against Rhipicephalus (Boophilus) decoloratus (ID # 42)

Wednesday, April 22, 2015, 11.00 – 11.15 am

M.M. Murigu1,2*, P. Nana1,3, R.M. Waruiru2, J.C. Nganga2, S. Ekesi1 and N.K. Maniania1

1International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya

2University of Nairobi, Department of Veterinary Pathology, Microbiology& Parasitology, P.O. Box 29053-00625 Kangemi-Nairobi

3Faculty of Agriculture and Agricultural Sciences, School of Wood, Water and Natural Resourse, University of Dschang, P.O. Box 786, Ebolowa, Cameroon

*Corresponding author; Email: mmurigu@yahoo,com

In livestock farming, Rhipicephalus(Boophilus)decoloratus, the blue ticks are usually the first to develop resistance to acaricide, because they prefer cattle and are exposed to multiple treatments during their relatively short live cycle. Blue ticks cause serious economic losses in cattle industry in Kenya and East Africa in general. Traditional parasite control is primarily based on the use of chemical acaricides, which unfortunately have negative side effects. As alternative to acaricides, biological control has been proposed as an option. The use of entomopathogenic fungi is among the major alternatives being explored for management of ticks. The aim of this study was to asses the susceptibility of amitraz-resistant and amitraz-susceptible strains of Rhipicephalus(Boophilus)decoloratus to selected virulent entomopathogenic fungal (Beauveriabassiana and Metarhiziumanisopliae) isolates and evaluate the compatibility of the most virulent fungal isolate with different concentrations of Amitraz as the combination could be used as tool to manage tick resistance to acaricide. Conoidal suspensions (1x109 conidia ml-1) were prepared and R.decoloratusunfed larvae sprayed using a hand sprayer. Mortality was recorded everyday for one week. All the isolates were pathogenic to the amitraz-scusceptibleR.decoloratus ticks, causing mortality between 10 and 100% at day 7 post exposure. The lethal time for 50% mortality (LT50) ranged from day 2.6 to 5.2, where as, the LT95 values varied between day 5.2 and 9.8 depending on the isolate. The experimental isolates were pathogenic to the resistant strains of R. decoloratus, causing mortality between 10 and 100% after 7 days of exposure. The lethal time for 50% mortality (LT50) ranged from day 2.8 to 4.6 whereas, the LT95 values varied between day 4.12 and 7.9 depending on the fungal isolate. Results indicate that some isolates of B.bassiana and M.anisopliaeare highly pathogenic to susceptible and resistant strain of R. decoloratus, suggesting a potential for their use in the control of this tick. The results of the compatibility tests indicated that Amitraz is compatible with M.anisopliae isolate ICIPE 7 at all the concentrations tested. The combination between the fungus and Amitraz was able to induced 100% mortality in both susceptible and Amitraz-resistant strains of R. decoloratus larvae in 48 hours only. Therefore the results suggest a possibility of minimizing the negative effects of acaricide by combining sub-lethal doses of acaricide with the entomopathogenic fungus. In future, further research is required to do controlled studies to assess efficacy of the EPF in animals and evaluate environmental impacts of uses of the EPF in Kenya.

Keywords:Entomo-pathogenic fungi, Rhipicephalus(Boophilus)decoloratus, biocontrol,acaricide resistance, virulence