Enhanced pest ant control with hydrophobic bait

Authors: Vander Meer, Robert - Bob; Milne, David

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2016
Publication Date: 2/20/2017
Citation: Vander Meer, R.K., Milne, D.E. 2017. Enhanced pest ant control with hydrophobic bait. Journal of Economic Entomology. 110(2):567-574.

Interpretive Summary: The red imported fire ant, Solenopsis invicta (Buren) is the most studied and documented of five ant species listed among the 100 worst alien species in the world. This fire ant left most of its natural enemies behind in South America when it arrived in Mobile, AL in the 1930s and spread rapidly throughout the southeastern USA reaching population levels up to 10 times those found in its native South America. The large population densities, potent sting, and propensity for disturbed habitats led to direct conflict with human activities. Annual expenditures for imported fire ant control and repair of damage are >US$ 6 billion per year. Bait control methods were first developed by USDA in response to fire ants in the early 1960s. This technology has changed little in the subsequent decades, in spite of the drawback that the bait carrier rapidly breaks down when wet. A scientist of the Imported Fire Ant and Household Insect Unit at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL demonstrated that a new hydrophobic fire ant bait has significant advantages over the equivalent standard fire ant bait formulation that becomes ineffectual when wet. The standard and hydrophobic baits were applied in the early morning when heavy dew is normally found on the grass of the treatment areas. The hydrophobic bait has the potential to reduce the application restrictions placed on bait products currently available in the USA, due to potential moist/wet conditions. It also is likely useful for other invasive pest ants that infest tropical/subtropical of the USA and other parts of the world.

Technical Abstract: Ants occupy every ecological niche in the world where they contribute to the ecosystem, e.g., as scavengers and aerators of the soil. However, when they are transported, usually through human activities, to new locations they have powerful negative impacts on their adopted homeland. Five of the 17 land invertebrates listed among the worst invasive alien species are ants. The red imported fire ant, Solenopsis invicta (Buren) is the most studied and documented of these ant species. It left most of its natural enemies behind in South America when it arrived in Mobile, AL in the 1930s and spread rapidly throughout the southeastern USA reaching population levels up to 10 times those found in South America. The large population densities, potent sting, and propensity for disturbed habitats led to direct conflict with human activities. Annual expenditures for imported fire ant control and repair of damage are >US$ 6 billion per year. Bait control methods were first developed in response to fire ants in the early 1960s. This technology has changed little in the subsequent decades, in spite of the drawback that the bait carrier rapidly breaks down when wet. The southeast USA is wet, averaging about 125 cm of precipitation per year, thus bait labels have various guidance restricting applications based on potential wet conditions. Here we present experiments comparing a hydrophobic fire ant bait to the equivalent standard bait formulation for innate attraction and importantly in a field experiment under natural wet conditions in Florida (heavy dew on ground). Our results demonstrate a significant advantage for the hydrophobic bait under common wet conditions that could lift current bait application restrictions and increase the time a bait is available to the target pest ant. An effective hydrophobic ant bait would also fill an important gap in our ability to control invasive pest ant species that thrive in tropical/subtropical habitats, e.g., Wasmannia auropunctata, the little fire ant, and Anoplolepis gracilipes, the yellow crazy ant.