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Abstract
This paper reports on trials conducted to kill managed and feral honey bee (Apis mellifera) colonies to eradicate unwanted honey bee pests. The effectiveness of Pestigas‐P™ (natural pyrethrum) for the destruction of managed colonies was assessed. Pestigas‐P™ was effective when applied as a single 15‐s spray into an empty three‐quarter‐depth super and across the top of the frames. This allowed the gas to filter throughout the hive. Piperonyl butoxide (wax = 42.28 mg/kg, honey = 0.34 mg/kg, propolis = 9.2 mg/kg, floor scrapings = 270.34 mg/kg) and pyrethrum (wax = 21.3 mg/kg, honey = 0.06 mg/ kg, propolis = 6.8 mg/kg, floor scrapings = 172.4 mg/kg) residues were found in the hive but after 4 weeks these had no detectable effect on newly introduced honey bee colonies. Combined analyses of attractiveness, toxicity, and lethal time trials identified Ascend® 200SC (a.i. fipronil) as effective for depopulating feral honey bee colonies in New Zealand using poisoned baits. Ascend® 200SC is a slow acting stomach toxin. The effect of Ascend® on feral honey bee colonies was assessed in Canterbury, New Zealand in 2003. Nucleus colonies were placed between bait stations set out in a 4km2 grid. The stations were pre‐baited with sugar syrup which was replaced with sugar syrup containing fipronil (0.05 ml/litre) once 300 bees were foraging from a single bait station. In the autumn trial all 20 colonies died within 13 days of poisoning. After 6 weeks the effect of poisoned hives on the survival of newly introduced colonies was assessed. Five colonies were placed next to 10 poisoned hives in the original eradication area, five colonies were placed with 10 poisoned hives at least 4km from the original area, and an additional 10 colonies were placed at least 4km from the original area and 4 km apart. Introduced colonies are likely to die if they consume the stored fipronil in poisoned colonies. This persistent poisoning action increases the likelihood of a honey bee eradication attempt being successful, as the colonies that are not killed in the first round of poisoning may be poisoned by robbing honey containing fipronil from a previously poisoned hive. Fipronil remained toxic in honey for at least 26 months when stored at 0°C, 5°C, and 25°C.
