Evaluation Of Entomopathogenic Effects Of The Fungi, Metarhizium Anisopliae And Beauveria Bassiana For Biological Control Of Rhipicephalus (Boophilus) Decoloratus

Abstract

Rhipicephalus decoloratus causes heavy losses economically in livestock annually. Currently, control of ticks is done using acaricides but use of other alternatives such as biological control is being studied. Twelve fungal isolates; seven Metarhizium anisopliae and five Beauveria bassiana obtained from ICIPE Arthropod’s germplasm were pretested for their germination potential and conidial viability, results of which indicated that their viability ranged from 96.6 % for ICIPE 644 to 100% for ICIPE 9, ICIPE 7 and ICIPE 718. The mortality of fungal isolates that was pathogenic to amitraz-susceptible and amitraz-resistant strains of R. decoloratus larvae, ranged from 10.0 to 100% and 12.1 to 100%, respectively. For the selected fungal isolates, their LT50 values ranged between 2.6 to 4.2 days in amitraz-susceptible strains and from 2.8 to 3.9 days in amitraz-resistant strains. Amitraz-susceptible strain showed LC50 values of between 0.4 ± 0.1 and 200.0 ± 60 x 103 conidia ml-1 while, amitraz-resistant strains had LC50 values ranging from 0.1 ± 0.1 to 200.0 ± 31.0 x 103 conidia ml-1. ICIPE 7, M. anisopliae outperformed the other eleven isolates and was selected for amitraz compatibility and field studies. It was also shown to be compatible with amitraz. In the field study, four treatments; control, M. anisopliae alone, amitraz alone and combination of M. anisopliae and amitraz were applied on cattle. All the treatments significantly reduced tick numbers significantly on day 7, day 14, day 21 and day 28 in comparison with the control. Results of the present study demonstrated the potential value of fungal pathogens for tick control; further research is needed to determine the association of biological products with chemical products and ICIPE 7 should be improved for use as a mycoacaricide and it can manage the amitraz resistant strains of R. decoloratus