Time to root out those evil weevils

16:00, Mar 14 2014

One million clover root weevils are making their way to a farm near you.

AgResearch has accelerated its attack on clover root weevil and will hand out packs of parasitised weevils to farmers at field days in the region next week.

AgResearch scientist Colin Ferguson said further planned releases of the insect would be made across the region with the aim of achieving maximum impact.

"If we can make releases of clover root weevil infected with the Irish wasp parasite on up to 1000 Southland farms before winter, then we will have done as much as we possibly hope to this year.

"To do this we aim to collect up to 1 million parasitised clover root weevils over the next few months," Mr Ferguson said.

The weevils have been collected from Canterbury pastures and have already been infected by the Irish parasitic wasp, which is known to be highly effective in the bio-control of clover root weevil.


AgResearch scientist Dr Scott Hardwick, who leads the Lincoln-based clover root weevil collection team, said most of the weevils were already parasitised, but parasitism levels had been boosted by adding a few Irish wasps to the packs of 100 that were being made up for farm release.

Clover root weevil has caused widespread devastation to pastures in Southland, and parts of Otago, and its presence is characterised by shotgun-like notching in white clover, which is its preferred food source.

‘Unfortunately there is little that farmers can do by changing their management practices to minimise the impact of clover root weevil and there are no current effective pesticides," he said.

Mr Ferguson said farmers could use nitrogen fertiliser to boost pasture production and cover for the lack of clover, but there were no quick fixes and they should not adopt any unproven "miracle" cures.

Southland farmers could expect clover content to return to normal levels two to four years after the wasps' arrival on their farms.

Those who suspect they may have clover root weevil were urged to attend one of the four field days:

Monday, March 17: Waikoikoi Hall, 10am; Glenham Hall, 3pm.

Tuesday, March 18: Winton Salvation Army Hall, 10am; Mossburn Community Centre, 3pm.

The Southland Times