Delayed Toxicity as a Critical Factor in the Efficacy of Aqueous Baits for Controlling Argentine Ants (Hymenoptera: Formicidae)

Abstract

Boric acid, imidacloprid, and thiamethoxam in sucrose aqueous baits had different delayed toxicities to worker Argentine ants, Linepithema humile (Mayr). The concentrations required to produce an LT50 (time required to produce 50% mortality) within 1-4 d were 3.63-0.55% boric acid, 9.2 x 10(-3) to 7.1 x 10(-4)% imidacloprid, and 3 x 10(-4) to 2 x 10(-5)% thiamethoxam. The three toxicants were not repellent. Other laboratory trials showed that 1% boric acid, 5 x 10(-4) to 5 x 10(-3)% imidacloprid, and 1 x 10(-5) to 1 x 10(-3)% thiamethoxam had delayed toxic effects, whereas 0.5% boric acid and < 5 x 10(-3)% imidacloprid did not. Baits that provided an LT50 between days 1 and 4 were considered to have delayed toxic effects. The utility of aqueous sucrose baits and toxicants soluble in such systems and the negative impact of fast-acting toxicants on trail following, recruitment, trophallaxis, and control of Argentine ants are discussed.

Trail Pheromones in Pest Control

“…Solid baits, typically targeting protein-feeding ants, have been somewhat successful (Tollerup et al, 2005). However, many pest species, including the Argentine ant, primarily forage for sugars (Klotz et al, 2002), which necessitates the development of liquid baits (Rust et al, 2004). For these reasons, more effective and environmentally sound ant control practices are needed for vineyards, especially for managers developing sustainable farming practices.…”

“…Research on the potential for using odorants in this way has targeted the control of leaf cutting ants and the red imported fire ant (Vander Meer, 1996), but the current paradigm remains largely confined to improving the performance of toxic baits (Rust et al, 2004). New application technologies that deliver pheromones against invasive pest ants could help reduce our reliance on the use of insecticides for ant pest control in sensitive ecosystems or where insecticides are undesirable.…”

Determining the Foraging Range and Origin of Resurgence After Treatment of Argentine Ant (Hymenoptera: Formicidae) in Urban Areas

“…Nelson and Daane (2007) hypothesized that ant foraging on 25% sugar water peaks in spring. Rust et al (2000) showed that L. humile foraged 26-60% and 16-40% of available protein in summer and winter respectively, suggesting considerable seasonal differences in activity and bait preferences. Thus, further research should focus on repeating the study in spring and autumn to deduce whether increased labeled bait acceptance will translate to increased bait movement in the vineyard.…”

“…Specifically, this was done by counting the number of ants sitting at each bait matrice at every hour. For L. humile, Rust et al (2000) reported increased foraging activity in the afternoon compared to mornings, but this may be dependent on microhabitat temperatures, which may differ from in different habitats and has not been tested for L. humile, C. peringueyi, and A. custodienns in a South African context.…”

“…There is no documented control method for vine-nesting species in South Africa, but lowtoxicity baits could be a viable option, as the recruitment to food sources and subsequent food-sharing behavior of ants can be used to distribute toxicant through the colony no matter where the colony is located (HooperBui and Rust 2000; Rust et al 2004). Effective control of South African ants using baits of low toxicity is limited by inadequate knowledge on ant foraging activity and optimum bait station density.…”