VIRULENCE OF FUNGAL PATHOGENS (IMPERFECT FUNGI, HYPHOMYCETES) TO PEARPSYLLA (HOMOPTERA, PSYLLIDAE)

Entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin, Metarhi zium anisopliae (Metschnikoff) Sorokin, M. flavoviride (Gams & Rozsypa l), Paecilomyces fumosoroseus Wise) Brown & Smith, and Verticillium le canii (Zimmerman) Viegas were evaluated for pathogenicity and virulenc e to pear psylla, Cacopsylla pyricola (Foerster), nymphs using a detac hed-leaf bioassay. Isolates within B. bassiana and P. fumosoroseus wer e also compared. Conidia suspended in water were applied to first and second instars at various concentrations and evaluated 3, 5, and 7 d a fter application. All of the fungal isolates tested were pathogenic to pear psylla nymphs. B. bassiana, P. farinosus, and V. lecanii were si gnificantly more virulent than the Metarhizium spp. (mortality range 9 2.5-99.6% versus 42.3-54.7%, respectively, on 7 d at 10(7) conidia/ml) . Similarly, the LC50s did not significantly differ for all isolates e xcept the Metarhizium spp. and ranged between 1.4 x 10(2) - 2.0 x 10(4 ) conidia/ml on 7 d. Metarhizium spp. had significantly lower LC50s th an the other isolates, that ranged from 2.3 x 10(7) - 11.7 x 10(10) co nidia/ml on 7 d. The fastest acting isolate when applied at 10(7) coni dia/ml was P. fumosoroseus ARSEF #2658 with an LC50 of 1.8 d, which wa s significantly higher than other isolates except B. bassiana. The LC5 0 could not be calculated for M. anisopliae because percent mortality did not increase with time. Based on LC50, LT50, and percent mortality comparisons, P. fumosoroseus ARSEF #2658 was the most virulent fungal isolate followed by B. bassiana ARSEF #2860. The potential of these i solates as mycoinsecticides for the control of pear psylla nymphs in o rchards is discussed.