Virulence of Fungal Pathogens (Imperfect Fungi: Hyphomycetes) to Pear Psylla (Homoptera: Psyllidae)

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Abstract
Entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metschnikoff) Sorokin, M. flavoviride (Gams & Rozsypal), Paecilomyces fumosoroseus (Wise) Brown & Smith, and Verticillium lecanii (Zimmerman) Viegas were evaluated for pathogenicity and virulence to pear psylla, Cacopsylla pyricola (Foerster), nymphs using a detached-leaf bioassay. Isolates within B. bassiana and P. fumosoroseus were also compared. Conidia suspended in water were applied to first and second instars at various concentrations and evaluated 3, 5, and 7 d after application. All of the fungal isolates tested were pathogenic to pear psylla nymphs. B. bassiana, P. farinosus, and V. lecanii were significantly more virulent than the Metarhizium spp. (mortality range, 92.5–99.6% versus 42.3–54.7%, respectively, on 7 d at 107 conidia/ml). Similarly, the LC50s did not significantly differ for all isolates except the Metarhizium spp. and ranged between 1.4 × 102 – 2.0 × 104 conidia/ml on 7 d. Metarhizium spp. had significantly lower LC50s than the other isolates, that ranged from 2.3 × 107 – 11.7 × 1010 conidia/ml on 7 d. The fastest acting isolate when applied at 107 conidia/ml was P. fumosoroseus ARSEF #2658 with an LC50 of 1.8 d, which was significantly higher than other isolates except B. bassiana. The LC50 could not be calculated for M. anisopliae because percent mortality did not increase with time. Based on LT50, LT50, and percent mortality comparisons, P. fumosoroseus ARSEF #2658 was the most virulent fungal isolate followed by B. bassiana AHSEF #2860. The potential of these isolates as mycoinsecticides for the control of pear psylla nymphs in orchards is discussed.

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