Red imported fire ants (Hymenoptera: Formicidae) cover the insecticide-treated surfaces with particles to reduce contact toxicity

Authors: WEN, CHAO - South China Agricultural Univerisity; SHEN, LIMING - South China Agricultural Univerisity; Chen, Jian; ZHANG, JIANLONG - South China Agricultural Univerisity; FENG, YING - Forest Resources Conservation Center Of Guangdong Province; WANG, ZHONG - Forest Resources Conservation Center Of Guangdong Province; CHEN, XUAN - Salisbury University; CAI, JIACHENG - Salisbury University; WANG, LEI - South China Agricultural Univerisity; HE, YINGBAO - South China Agricultural Univerisity; WEN, XIUJUN - South China Agricultural Univerisity; MA, TAO - South China Agricultural Univerisity; WANG, CAI - South China Agricultural Univerisity

Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2021
Publication Date: 1/28/2022
Citation: Wen, C., Shen, L., Chen, J., Zhang, J., Feng, Y., Wang, Z., Chen, X., Cai, J., Wang, L., He, Y., Wen, X., Ma, T., Wang, C. 2022. Red imported fire ants (Hymenoptera: Formicidae) cover the insecticide-treated surfaces with particles to reduce contact toxicity. Journal of Pest Science. 95:1135-1150. https://doi.org/10.1007/s10340-021-01474-0.
DOI: https://doi.org/10.1007/s10340-021-01474-0

Interpretive Summary: The red imported fire ant is a significant pest. Surface treatment using contact-based synthetic insecticides is a common practice in controlling the red imported fire ants. In the present study, the behavioral responses of fire ants to surfaces treated with insecticides were investigated. It was found that fire ants were able to use the soil particles to cover the surfaces treated with insecticides while they are foraging. This behavior can significantly reduce the effect of certain insecticides on fire ants. This study provides the first evidence for such unique insecticide resistance strategy in ants. Behavioral resistance to insecticides must be considered in developing fire ant control products in the future.

Technical Abstract: Surface treatment is commonly used in controlling the red imported fire ants, Solenopsis invicta Buren. In the present study, the behavioral responses of S. invicta workers to surfaces treated with insecticides were investigated. Toxicological tests showed that beta-cypermethrin had the highest contact toxicity (with the lowest LC50 value) among nine tested insecticides, followed by thiamethoxam, fipronil, indoxacarb, chlorfenapyr, rotenone, spinetoram, avermectin, and chlorantraniliprole. In the laboratory, surfaces treated beta-cypermethrin or rotenone significantly reduced the number of foraging ants. In addition, S. invicta workers transported significantly more particles (measured in weight and/or covered area) onto surfaces treated with fipronil (50, 500, and 5000 ppm), rotenone (5000 ppm), or avermectin (5000 ppm) compared with the controls. Similarly, these insecticides significantly triggered the particle-covering behavior of ants in the field. We hypothesized that such behaviors would reduce the contact toxicity of insecticides against S. invicta. When the surfaces treated with fipronil or rotenone (500 or 5000 ppm) were artificiality covered with particles, S. invicta had significantly higher LT50 values compared with insecticide-treated surfaces without particles. This study provides the first evidence that S. invicta workers can perform particle-covering behavior to reduce the toxicity of certain insecticides, which constitutes a unique insecticide-resistance strategy in ants.