EVALUATION OF EXPERIMENTAL FIPRONIL BAITS FOR CONTROL OF PHARAOH’S ANTS IN CZECH REPUBLIC

Abstract:
The Pharaoh’s ant Monomorium pharaonis (L.) (Hymenoptera: Formicidae) is a widespread urban pest, being most common in large, heated buildings. Fipronil is a novel phenyl-pyrazole insecticide, effective against insects of urban importance including termites and cockroaches, being active by both oral and contact routes. Laboratory and field tests have been carried out in Czech Republic, to assess the effectiveness of fipronil as a bait formulation for Pharaoh’s ant control. Small colonies of Pharaoh’s ants, each consisting of queens, workers, and immature stages, were established in 150 mm diameter petri dishes, and supplied with laboratory diet. Replicate nests were offered either fipronil formulations made from various food bases (A or B), or commercial hydramethylnon bait. At intervals the mortality of the ants was assessed: Table1. Ant numbers following treatment of laboratory nests. weeks after introduction of bait Formulation ai conc. % pretreatment 1 2 3 4 6 10 15 fipronil A 0.001 900 107 7 0 0 - - - fipronil B 0.001 1000 1000 950 700 750 800 950 910 hydramethylnon 0.95 750 510 255 245 310 290 640 775 untreated 0 675 675 675 775 875 1000 - - To determine efficacy under field conditions, ants in infested housing blocks were monitored before and after treatment. Commercial hydramethylnon baits were applied at 5 per apartment following label recommendations, while fipronil baits were applied at ca.10 bait portions/apartment. Each treatment was applied to a block of ca.20 infested apartments. Table 2. % of ant monitoring tubes positive for ants following field treatments. weeks after treatment Bait ai conc. % pretreatment 2 4 7 11 15 33 fipronil A 0.001 65 3 0 0 0 0 0 fipronil B 0.001 36 28 22 7 8 6 15 hydramethylnon 0.95 55 53 19 29 19 17 25 untreated 0 67 56 65 75 77 67 - In conclusion, fipronil bait efficacy is influenced by the choice of food base. However, in a suitable bait base, even low fipronil rates appear very effective and fast acting against Pharaoh’s ants, showing greater activity than commercial reference products. Development continues, in order to finalise the fipronil formulation.