TRIALS to ERADICATE INFESTATIONS of the ARGENTINE ANT, LINEPITHEMA HUMILE

Abstract The Argentine ant (Linepithema humile) is a highly invasive species, a major urban pest, and capable of impacting native systems. It was first found in New Zealand in 1990, and in March 2000, a population was discovered on a 200-ha island reserve of conservation significance. This led to a call for the development of a strategy to eradicate infestations of Argentine ants. In summer 2001 (January-March) five isolated infestations, three in urban industrial sites and two in coastal scrub vegetation were treated with single applications of protein bait incorporating the insecticide fipronil (0.01%). Application rates were higher in the coastal habitat (~6 kg/ha) than the urban areas (2.5 to 3 kg/ha). The abundance of ants was monitored at all treatment sites, a non-treatment site with Argentine ants, and three non-treatment sites without Argentine ants. At all treatment sites Argentine ant numbers were reduced to very low levels (< 1% of pre-treatment levels on non-toxic baits) and 9 months after treatment ant numbers remained low. Re-treatment is necessary to achieve eradication and is underway at some of the sites. Additional trials using the same bait but with a lower concentration of fipronil are also underway to determine if this modification will result in eradication following initial treatment. Key Words Baiting Fipronil Eradicatio