The use of entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, as bio-pesticides for tick control

Abstract

This paper reports promising results on the use of entomopathogenic fungi for tick control. The aqueous formulations of the entomopathogenic fungi, Metarhizium anisopliae isolate RS2 and Beauveria bassiana isolate NM2 induced mortalities ranging from 36-64% in adult Rhipicephalus (Boophilus) appendiculatus and 40-50% in Boophilus decoloratus in the laboratory. In Rhipicephalus evertsi evertsi, mortality increased with conidial concentration in all tick stages and oil formulation outperformed (p<0.05) the aqueous formulation in all experiments. In the field potted grass experiment, both aqueous and oil formulations of M. anisopliae and B. bassiana induced high mortalities in R (B). appendiculatus and Amblyomma variegatum, especially in larvae, where mortality reached 100% in both tick species. In nymphs of both R (B). appendiculatus and A. variegatum, mortality was about 100% with oil and 80% with aqueous formulations (p<0.05), whereas in adults, mortality was 20-40% (aqueous) and 65-100% (oil), respectively. In the semi-field experiment, ticks (R (B). appendiculatus) feeding on cattle were sprayed with fungi (aqueous formulation) and allowed to continue feeding until they drop off. Half of the dropped off ticks were maintained in the field and the rest in the laboratory and the fungi induced significant mortalities and reduced fecundity and egg hatchability in both categories but the results were not significantly different from each other (p>0.05). In the field paddocks sprayed with B. bassiana and M. anisopliae tick counts were much lower than those in the control paddock (p<0.05). After monthly spraying for 6 months, the mean numbers of adult R (B). appendiculatus on cattle were reduced by 80% in B. bassiana and 92% in M. anisopliae sprayed paddocks compared to control paddock. These observations show that M. anisopliae and B. bassiana, have potential as tick mycopesticides