Bait insecticides and hot water drenches against the Little Fire Ant, Wasmannia auropunctata (Hymenoptera: Formicidae), infesting containerized nursery plants

Broadcasts of hydramethylnon, S-methoprene, and metaflumizone baits, metaflumizone spray, and hot water drenching were evaluated for their efficacy against the little fire ant, Wasmannia auropunctata (Roger), in potted nursery plants. Two applications one month apart of either a bait containing 0.365% hydramethylnon and 0.25% S-methoprene (Extinguish Plus) or a spray containing 24% metaflumizone (BAS 320 I 240 SC) reduced foraging worker numbers by >97% as compared with untreated controls. The persistence of weather-exposed metaflumizone (0.063%) bait was also evaluated: bait applied fresh or after 7 days of weather exposure resulted in >98% ant mortality; bait exposed to weather for 14 d before application still achieved >90% mortality. In vitro submersion of W. auropunctata in 45°C water for 10 min resulted in >99% mortality as compared with 28.9% mortality from submersion in ambient temperature water (26°C) for 12 min. When W. auropunctata -infested potted plants were drenched with hot water (45.6°C) for 11 min, the number of live ants were reduced by 99.3 and 89.3% in rhapis and fishtail palm, respectively, as compared with control plants drenched with ambient temperature water. The presence of a single W. auropunctata worker in a potted plant would fail to meet export requirements; therefore, the chemical baits and sprays and hot water treatment (45.6°C for 11 min) as evaluated in this study would not individually be a sufficient quarantine protocol against little fire ants in containerized nursery plants.