Characterization of Beauveria bassiana and Metarhizium anisopliae isolates for management of tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae)

Selected morphological and physiological characteristics of four Beauveria bassiana (Balsamo) Vuillemin isolates and one Metarhizium anisopliae (Metschnikoff) Sorokin isolate, which are highly pathogenic to Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), were determined. There were significant differences in conidial size, viability, spore production, speed of germination, relative hyphal growth, and temperature sensitivity. Spore viability after incubation for 24 h at 20 degreesC ranged from 91.4 to 98.6% for the five isolates tested. Spore production on quarter-strength Sabouraud dextrose agar plus 0.25% (w/v) yeast extract after 10 days incubation at 20 degreesC ranged from 1.6 x 10(6) to 15.5 x 10(6) conidia/cm(2). One B. bassiana isolate (ARSEF 1394) produced significantly more conidia than the others. Spore germination was temperature-dependant for both B. bassiana and M. anisopliae. The time required for 50% germination (TG(50)) ranged from 25.0 to 30.9, 14.0 to 16.6, and 14.8 to 18.0 h at 15, 22, and 28degreesC, respectively. Only the M. anisopliae isolate (ARSEF 3540) had significant spore germination at 35degreesC with a TG(50) of 11.8 h. A destructive sampling method was used to measure the relative hyphal growth rate among isolates. Exposure to high temperature (40-50 degreesC) for 10 min had a negative effect on conidial viability. The importance of these characteristics in selecting fungal isolates for management of L. lineolaris is discussed. (C) 2003 Published by Elsevier Science (USA).