Scientists are to ask the Environmental Risk Management Authority (ERMA) to approve the release of a tiny Irish parasitoid wasp to control an invasive pest threatening this country’s economic wellbeing.

Sitona lepidus, or clover root weevil an overseas invader, was first discovered here in 1996. It’s believed the introduction was accidental, probably in a shipping container.

As the name suggests clover root weevil feeds on white clover.

It is already a significant problem in the North Island where clover content typically has declined from an average 20% to 10% because of the weevil.

This weevil is putting productivity, profitability and New Zealand’s clean green image at risk. Scientists warn it is only a matter of time before it spreads to the South Island..

Scientist Dr Pip Gerard says “even city dwellers are aware the rise and fall of the economy depends largely on the fortunes of the farming community.

 “Well clover is key part of our competitive edge – animals love it so they eat more of it – and their butter, milk, meat and wool production is the better for it.”

 It also fixes nitrogen to maintain soil fertility.

“If we allow the clover root weevil to compromise the benefits of clover and we become dependent of artificial fertilisers to maintain productivity – we not only risk our ‘green’ image we significantly impact on farm economics”.

Conservative estimates put the cost to the country, in lost productivity and profitability, (if the weevil takes hold nationwide) at around $300 million a year. For individual farmers a 10% reduction in clover cover equates to over $100 less return for each affected hectare annually.

On top of that is the environmental damage from increased run-off into waterways of higher levels of fertiliser farmers in infested areas now have to apply, to counter the loss of ‘natural’ nitrogen the clover would normally put into the soil.

Scientists at AgResearch have spent the past seven years researching a possible solution to the problem.

The Research Institute is now seeking permission to release a biocontrol it believes is the breakthrough farmers have been waiting for.

It’s a parasitic wasp, Microctonus aethiopoides, that attacks the adult weevil. Microctonus loosely translates to ‘little killer’.

Pip Gerard says experiments have shown it can indeed kill the clover root weevil and is no more harmful to native weevils and other biological control insects than any other agents already released in this country.

 (A strain of the same parasitoid is already proving effective against the lucerne pest Sitona discoideus.)

An application is expected to go before the Environmental Risk Management Authority (ERMA) by the middle of next month.

If approved AgResearch hopes to begin experimental releases.

AgResearch’s work on the biocontrol agent has been funded by Dairy Insight, the Foundation for Science and Technology (FRST), Meat and Wool New Zealand, Deer Industry New Zealand, AGMARDT, and the C.Alma Baker Trust.