title: Laboratory and field evaluation of entomopathogenic fungi for the control of amitraz-resistant and susceptible strains of Rhipicephalus decoloratus.
abstract: Rhipicephalus decoloratus causes serious economic losses in cattle industry every year in East Africa. Biological control using entomopathogenic fungi is seen as a promising alternative to chemical acaricides being used for their control. The pathogenicity of Metarhizium anisopliae and of Beauveria bassiana isolates was tested in the laboratory against amitraz-resistant and amitraz-susceptible strains of R. decoloratus. Unfed larvae were sprayed with conidial suspensions of 1×10(9) conidia ml(-1). Fungal isolates were pathogenic to R. decoloratus larvae, causing mortality of between 10.0 and 100% and between 12.1 and 100% of amitraz-susceptible and amitraz-resistant strains, respectively. The LT50 values of selected fungal isolates varied between 2.6-4.2days in amitraz-susceptible strain and between 2.8-3.9days in amitraz-resistant strain. The LC50 values varied between 0.4±0.1 and 200.0±60×10(3) conidia ml(-1) and between 0.1±0.1 and 200.0±31.0×10(3) conidia ml(-1) in amitraz-susceptible and amitraz-resistant strains, respectively. Metarhizium anisopliae isolate ICIPE 7 outperformed the other isolates and was selected for compatibility study with amitraz and field trial. ICIPE 7 was compatible with amitraz. In the field, four treatments including control, ICIPE 7 alone, amitraz alone and ICIPE 7/amitraz were applied on cattle. All the treatments significantly reduced the number of ticks on all the sampling dates: day 7 (F3,8=3.917; P=0.0284), day 14 (F3,8=9.090; P=0.0275), day 21 (F3,8=37.971; P=0.0001) and day 28 (F3,8=8.170; P=0.0016) compared to the control. Results of the present study indicate that ICIPE 7 can be used for the management of amitraz-resistant strain of R. decoloratus.
authors.affiliation: International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya; University of Nairobi, Department of Veterinary Pathology, Microbiologyand Parasitology, P.O. Box 29053-00625, Kangemi-Nairobi, Kenya.
authors.forename: Mercy M
authors.initials: MM
authors.lastname: Murigu
authors.affiliation: International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya; University of Dschang, Faculty of Agriculture and Agricultural Sciences, School of Wood, Water and Natural Resources, P.O. Box 786, Ebolowa, Cameroon.
authors.forename: Paulin
authors.initials: P
authors.lastname: Nana
authors.affiliation: University of Nairobi, Department of Veterinary Pathology, Microbiologyand Parasitology, P.O. Box 29053-00625, Kangemi-Nairobi, Kenya.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Waruiru
authors.affiliation: University of Nairobi, Department of Veterinary Pathology, Microbiologyand Parasitology, P.O. Box 29053-00625, Kangemi-Nairobi, Kenya.
authors.forename: Chege J
authors.initials: CJ
authors.lastname: Nga'nga'
authors.affiliation: International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya.
authors.forename: Sunday
authors.initials: S
authors.lastname: Ekesi
authors.affiliation: International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya. Electronic address: nmaniania@icipe.org.
authors.forename: Nguya K
authors.initials: NK
authors.lastname: Maniania
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000187:drug effects / Q000382:microbiology*; D052982:Beauveria / Q000472:pathogenicity*; D004351:Drug Resistance; D052981:Metarhizium / Q000472:pathogenicity*; D010572:Pest Control, Biological / Q000592:standards*; D048494:Rhipicephalus / Q000187:drug effects / Q000382:microbiology*; D014052:Toluidines / Q000494:pharmacology
chemical_list: D014052:Toluidines; C014983:amitraz
keywords: Acaricide; Beauveria bassiana; Biocontrol; Metarhizium anisopliae; Rhipicephalus decoloratus; Tick