PATHOGENICITY OF THE ENTOMOPATHOGENIC FUNGI PAECILOMYCES SPP. AND BEAUVERIA-BASSIANA AGAINST THE SILVERLEAF WHITEFLY, BEMISIA-ARGENTIFOLII

Pathogenicities of three species of entomopathogenic fungi against pre imaginal Bemisia argentifolii were measured and compared. Third-instar nymphs on excised leaves of Hibiscus rosa-sinensis were exposed to sp ray applications of 14 isolates of Beauveria bassiana, 22 isolates of Paecilomyces fumosoroseus, and five isolates of Paecilomyces farinosus . B. bassiana and P. fumosoroseus isolates of diverse origins were hig hly pathogenic to the whitefly nymphs; median lethal doses of 14 of th e 22 P. fumosoroseus and four of the 13 B. bassiana isolates ranged be tween 50 and 150 conidia/mm(2). Five isolates of P. farinosus were als o pathogenic; however, LC(50)s were relatively high, ranging between 3 50 and 4000 conidia/mm(2). Nymphs infected with all but one isolate of B. bassiana displayed a pronounced red pigmentation. Postmortem hypha l growth and sporulation of B. bassiana was relatively slow and usuall y confined to the region immediately surrounding the dead host. Whitef ly nymphs patently infected with P. fumosoroseus and P. farinosus were lightly pigmented yellow or orange. Postmortem hyphal growth and spor ulation of P. fumosoroseus rapidly covered the dead host and extended several millimeters onto the surrounding leaf surface. The results ind icate that highly virulent strains of P. fumosoroseus and B. bassiana with considerable whitefly control potential are widespread and numero us. (C) 1998 Academic Press.