Novel Beauveria bassiana delivery system for biological control of the red imported fire ant

The red imported fire ant (Solenopsis invicta Buren; Hymenoptera: Formicidae) is a major pest throughout the southern United States, in part, because few natural enemies are present. The entomopathogenic fungus, Beauveria bassiana, caused significant mortality in the laboratory, but the fungus was less effective in field trials, perhaps because ants did not remain in contact with fungus long enough to become infected. In previous experiments, S. invicta removed unbaited fungal alginate pellets that were placed directly into mounds, resulting in no reduction in fire ant populations. However, baiting pellets with peanut oil improved delivery of the biological control agent and reduced fire ant populations in heavily infested cattle pastures. In the study reported herein, we have developed another method of B. bassiana delivery directly into fire ant mounds, targeting individual colonies. Placing wooden craft sticks or wooden marking stakes coated with B. bassiana effectively killed fire ants and rendered most mounds inactive.