They aim to collect up to one million parasitised weevils over the next few months to release on to 1000 Southland farms before winter to kill off the weevils there.
The vacuumed up weevils were infected with the Irish wasp parasite.
“While most of these collected weevils are already parasitised, we boost the parasitism levels by adding a few Irish wasps to the packs of 100 we make up for farm release,” AgResearch scientist Dr Scott Hardwick said.
Hardwick advised farmers not to worry if their farm is not one of the selected release sites.
“In Canterbury and North Otago we have seen the Irish wasp spreading up to 30km per year from release sites, so even if your farm is not one of selected release sites, the Irish wasp released on your neighbour’s farm will quickly arrive on your farm.”
Beef + Lamb New Zealand are holding weevil field days next week:
March 17 – Waikoikoi at 10am, and Glenham at 3pm.
March 18 – Winton at 10am, and Mossburn at 3pm.
AgResearch pest specialist and scientist, Colin Ferguson, said last year’s mild winter had seen the weevil population, which has been present in Southland since 2010, explode.
“The mild conditions allowed a greater number of weevil eggs to hatch and more of the larvae survived right through the winter,” he said.
There was little farmers could do to minimise the impact of weevils.
There were no effective pesticides.
“If the farm budget allows, farmers can use nitrogen fertiliser to boost pasture production and cover for the lack of clover.”
The lack of clover was having a huge impact on farm returns right now, he said.
“Affected farmers were either seeing clover that disappears very quickly once grazed, or a complete absence of clover plants in their pasture.
“Without clover farmers can’t fatten lambs, and those that are looking to winter dairy grazers can’t do that.”
He said Southland farmers could expect clover content to return to normal levels two-to-four years after the wasps’ arrival on their farms.”
The weevil population has reduced by more than 90% in monitored North Island farms where the wasp has been released.
