Submitted to: Entomological Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 29, 2003
Publication Date: October 29, 2003
Citation: Bailey, E.J., Behle, R.W. 2003. Comparison of spore germination of Beauveria bassiana and insecticidal activity against Trichoplusia ni (Hubner) [abstract]. Entomological Society of America Annual Meeting. Abstract No. D0587. p. 123. Technical Abstract: The relationship between spore germination of Beauveria bassiana and insecticidal activity against Trichoplusia ni (Hübner) neonates was explored to determine a faster screening method for Beauveria bassiana formulations. Spore germination was altered by degrading spores in various ways, including exposure to heat, exposure to high and low pH, spray drying, and room temperature storage. To determine germination, spores were suspended in nutrient broth and shaken at 28ºC for 14 hours. The spores were then examined for presence of a germ tube under a light microscope to determine the percentage germination. Percentage germination ranged from 18% to 88%. To determine insecticidal activity (LC50), five concentrations per treatment were formed by serial dilution. For each treatment x concentration, 90 neonate T. ni were exposed to treated bean leaf disks for 24 hours. After exposure, larvae were transferred to artificial diet and incubated at 28ºC. Five days after initial exposure to the spores, larvae were examined for live and dead. LC50 values were calculated using POLOPC and ranged from 1.5 x 10(7) to 2.3 x 10(8). Regardless of the mode of degradation, treatments with lower germination percentages typically had lower insecticidal activity. High correlation between germination percentage and LC50 suggests that a 14-hour germination assay can be used for faster screening of Beauveria bassiana formulations in lieu of a 5-day insecticidal activity assay.