A modified method to visualize infection sites of spores of the entomopathogen Beauveria bassiana adults

• Published in: The Florida entomologist Vol. 92; no. 4; pp. 623 - 1245
• Main Authors: Gillett-Kaufman, Jennifer L, Kimbrough, James W
• Format: Journal Article
• Language: English
• Published: Florida Entomological Society 01.12.2009
• Subjects: Agricultural pests; Biological control; Contact tracing; Control; Fungi, Pathogenic; Health aspects; Methods; Natural history; Pests; United States
• ISSN: 0015-4040; 1938-5102

Beauveria bassiana is a widespread entomopathogen which is infectious to a great variety of insects. A commercial preparation of this fungus was used to study its potential as a biocontrol agent of the citrus root weevil, Diaprepes abbreviatus. Laboratory reared adult weevils were placed in clean plastic bags with 0.05 g of powdered inoculum per bag, shaken for thirty seconds, and placed in holding cages. In order to determine the spore concentration, germination, and position of ingress, inoculated weevils were dipped in a collodion solution after 30 min, 6 h, 12 h, 18 h, and 30 h. Collodion peels from various areas of the exoskeleton were removed, stained with lactophenol cotton blue, and observed microscopically. At 12 h post-inoculation, spores began to swell, and at 18 h close to 25% germinated on all body parts except on the elytra. After 30 h, between 45% and 75% of the spores germinated, depending on the body part. Most active spore germination occurred around the eyes (75%), followed by the ventral abdomen (65%), the dorsal pronotum (60%), scales (45%), and dorsal surface of the elytra (7%). Spores were washed from the surface of inoculated weevils with distilled water and plating onto potato dextrose agar. Spore density on the weevils' surface was determined to be 15,815.t 479 spores initially after inoculation, and was reduced to 5,782 ± 136 spores after 3 h.