Effect of irrigation on the control of red imported fire ants (Hymenoptera: Formicidae) by water-resistant and standard fire ant baits

Authors: Oi, David; Atchison, Rachel; CHUZEL, GERALD - Coachella Valley Mosquito And Vector Control District; Chen, Jian; HENKE, JENNIFER - Coachella Valley Mosquito And Vector Control District; WEEKS, RONALD - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2021
Publication Date: 2/9/2022
Publication URL: https://handle.nal.usda.gov/10113/7674423
Citation: Oi, D.H., Atchison, R.A., Chuzel, G., Chen, J., Henke, J.A., Weeks, R.D. 2022. Effect of irrigation on the control of red imported fire ants (Hymenoptera: Formicidae) by water-resistant and standard fire ant baits. Journal of Economic Entomology. 115(1):266-272. https://doi.org/10.1093/jee/toab242.
DOI: https://doi.org/10.1093/jee/toab242

Interpretive Summary: The red imported fire ant is an invasive pest of agricultural, urban, and natural areas. It is also considered a public health pest due to its painful stings. It can be efficently contolled by commercially availible fire ant baits which typically contain corn grit, a key ingredient that allows the bait to be easily applied and readily collected by ants. However, it is traditionally thought that the corn grit degrades when exposed to rain or irrigation and fire ant control does not occur because thebait is not harvested by the ants. As a result, water-resistant fire ant baits have been developed that either replace or modify the corn grit. Research conducted by ARS, APHIS, and the Coachella Valley Mosquito and Vector Control District determined that both standard commercial fire ant bait and water-resistant baits that have been soaked in water in the labratory, as well as exposed to sprinkler irrigation in landscpaes, can still effectively control fire ants. Because water-resistant fire ant baits are not readily availible in the U.S., knowledge that standard fire ant baits can withstand sprinkler irrigation should offer land managers and groundkeepers more flexibility in implementing fire ant control programs.

Technical Abstract: The red imported fire ant, Solenopsis invicta (Buren), is an invasive pest of agricultural, urban, and natural areas. It is also considered a public health pest due to its painful stings. It can be efficently controlled by commercially availible fire ant baits which are typically formulated with a corn grit carrier. The carrier is throught to degrade when exposed to rain or irrigation, and thus compromises bait effectiveness. To assess the effect of irrigation on the efficacy of wwater-resistant and standard fire ant bait formulations, the number of workers, brood volume, annd queen survivorship were compared after access to water-soaked baits and to bait treated sod that was irrigated. In itial testing, fire ant reductions were less in colonies presented water-soaked baits dirrectly and in colonies given access to baits broadcasted (i.e., scattered) atop sod followed by irrigation, for both the water-resistant and standard baits when compared to dry baits. Comparisons of the efficacy of piled versus broadcast applications of water-resistant and standard baits reavealed reductions of >88% in adult and brood and no surviving queens for all bait treatments. This resul;t was unexpected because piled baits were hypothesized to be better protected from irrigation than broadcast bait applications. In a field study, irrigated water-resistant and standard baits caused similar and significantly higher reductions in fire ant activity relative to an untreated control. These results indicated that both the water-resistant and standars fire ant bait provided significant fire ant reductions even after irrigation.