Clover root weevil update 5 years on

It has been over ten years since clover root weevil munched a devastating swathe through the Waikato, Bay of Plenty and Auckland regions, earning its reputation as the "˜Evil weevil'. Since then, it has spread throughout the North Island and in 2006, established footholds in Nelson and Canterbury.But in 2006 AgResearch entomologists also released a biocontrol agent "“ a tiny Irish wasp - to help strike back at the weevil. It is now three years on. Who is winning the war "“ the weevil or the clover? The use of nitrogen fertiliser is the quickest way to ensure feed supply and maintain farm profitability in weevil-infested regions. With clover root weevil present in the system, nitrogen fertiliser enhances both clover and grass production. The use of nitrogen fertiliser is not an option for all farm systems. Consequently, a long term economically and environmentally sustainable solution for clover root weevil was required to ensure farmers could benefit from the animal production and nitrogen-fixing advantages of clovers. AgResearch entomologists released the Irish parasitoid wasp Microctonus aethiopoides at experimental sites in the Waikato, Hawke's Bay and Manawatu in early 2006. This tiny wasp attacks adult weevils, rendering females sterile almost immediately and breaking the life cycle. The host dies when the wasp larva emerges to pupate. The wasp has done extremely well at all these sites, even with the drought earlier this year. It has spread at least 15 km from the Hawke's Bay release site and 11 km from the Bulls release site. Following this great start, two strategies were implemented to spread the Irish wasp throughout the North Island as fast as possible. One approach was the establishment of regional nursery sites that act as point sources for natural and assisted dispersal.