PROSPECTS FOR BIOLOGICAL-CONTROL OF LIVESTOCK TICKS, RHIPICEPHALUS-APPENDICULATUS AND AMBLYOMMA-VARIEGATUM, USING THE ENTOMOGENOUS FUNGI BEAUVERIA-BASSIANA AND METARHIZIUM-ANISOPLIAE

Both Beauveria bassiana and Metarhizium anisopliae induced approximate ly 30% mortalities in adult Rhipicephalus appendiculatus feeding on ra bbits while M. anisopliae induced a mortality of 37% in adult Amblyomm a variegatum. Both fungal species induced reductions in engorgement we ights, fecundity, and egg hatchability in adult A. variegatum. M. anis opliae reduced fecundity by 94% in A. variegatum. Furthermore, B. bass iana reduced egg hatchability to 0%, while 11% of the infected females failed to lay eggs. In Zebu cattle naturally infested, with R. append iculatus in the field, both B. bassiana and M. anisopliae induced high mortalities ranging from 76-85%, a remarkable reduction in fecundity (85-99%), and a significant reduction in egg hatchability (94-100%). W hen incubated in organophosphate acaricides for up to 120 hr, both fun gi retained their normal growth and morphological characteristics. B. bassiana and M. anisopliae persisted on cattle ears for 1 and 3 weeks, respectively, after application. Both B. bassiana and M. anisopliae i nduced a mortality of approximately 100%, 76-95% and 36-64% in larvae, nymphs, and adults, respectively, of R. appendiculatus seeded in gras s in the field. Spores of B. bassiana and M. anisopliae mixed with ste rilized sand and maintained at 0 and 25 degrees C maintained good viab ility for over 12 months (B. bassiana) and for 8 months (M. anisopliae ) and no significant difference was observed in spores stored in the t wo different temperatures. (C) 1996 Academic Press, Inc.