Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2011
Publication Date: 6/1/2012
Publication URL: http://handle.nal.usda.gov/10113/61796
Citation: Chen, J., Rashid, T., Feng, G. 2012. Toxicity of formic acid against red imported fire ants, Solenopsis invicta Buren. Pest Management Science. 68:1393-1399. doi: 10.1002/ps.3319. Interpretive Summary: Red imported fire ants are a serious pest insect affecting humans, wildlife, crops, and livestock. Synthetic insecticides are commonly used to control fire ants. One major concern in using these insecticides is their negative effect on the environment. As a safer or “green” alternative, naturally-derived compounds have a great potential in fire ant management. Formic acid is a common defensive chemical of certain ants. In this study, it was found that formic acid had a significant fumigation toxicity against the red imported fire ant. Formic acid may be applicable to the management of fire ants, such as in aerosol injection application for mound treatment and fumigation for potted nursery plants.
Technical Abstract: BACKGROUND: Formic acid is a common defensive chemical of formicine ants. Ants often compete with other ants for resources. However, the toxicity of formic acid to any ant species has not been well understood. This study examined the toxicity of formic acid against the red imported fire ants, Solenopsis invicta Buren. RESULTS: Formic acid had low contact toxicity against red imported fire ants. The 24-h LD50 values ranged from 105.7 to163.5 µg/ant for workers. Female alates and queens were much less sensitive to formic acid than workers. At the concentration of 232.0 µg/ant, the 24-h mortality was 25.08% to 39.64% for female alates and 0.00% to 38.89% for queens. In fumigation bioassays, at the concentration of 1.78 nL/mL, KD50 values at ranged from 23.03 to 43.85 min for workers, 37.84 to 58.37 min for male alates, 86.06 to 121.05 min for female alates and 55.26 to 73.80 min for queens. Lower KD50 values were observed at 14.26 nL/mL, KD50, which ranged from 8.64 to 12.76 min for workers. 24-h LC50 values ranged from 0.19 to 0.42 nL/mL for workers, 0.27 nL/mL for male alates and 0.60 nL/mL for female alates. Formic acid caused 100% mortality among queens at the concentration of 1.34 nL/mL. CONCLUSION: Formic acid had very low contact toxicity against the red imported fire ants, in contrast with high fumigation toxicity. It may be applicable to the management of fire ants, such as in aerosol injection application for mound treatment and fumigation for potted nursery plants.