Dairy farmers warned about clover root weevil

1.00pm

Waikato dairy farmers have been fighting the effects of clover root weevil for eight years and it is now spreading.

The weevil was first found in the Waikato in 1996, and has been spreading through the North Island since then -- New Zealand's temperate climate and a lack of predators provide ideal conditions for the weevil.

Last year, it was found in Taranaki, and last week, Agresearch plant breeder Chris Mercer found clover root weevil specimens on the roadside of State Highway One near Marton, and at a site in Palmerston North.

Severe weevil infestations can eradicate from pastures the white clover on which farmers depend for high quality pasture and the "free" fixation of atmospheric nitrogen to boost plant growth.

Waikato Clover Management Group chairwoman, Lorraine Bilby this week ran a seminar for Taranaki farmers coming to grips with the pest.

Mrs Bilby -- who first encountered clover root weevil on her farm in 1996 and lost a huge amount of production -- said farmers in regions where the pest had newly established faced a drop of up to 30 per cent in production.

If they did not yet have the pest, it was only a matter of time before it arrived, and she said the Government and other major industry players were not doing a great deal to combat the problem.

Other participants in the seminar included: Agresearch entomologist Bruce Willoughby, who has worked for the group without funding; former dairy company director Keith Holmes, who said he was angry at the lack of urgency with which the clover root weevil problem was being treated; and Craig McKie, a 50:50 sharemilker who applies nitrogen to his farm twice a week to combat the weevil's effects.

Mrs Bilby said Taranaki farmers needed to consider the formation of a similar group as the impact of clover root weevil in their region grew.

"You have to be proactive and not let this pest eat away at your profits. There is no silver bullet available from current research and it is up to those affected to form groups to help get funding and stay viable."

Dr Willoughby said clover root weevil was now well established in the northern North Island and would eventually spread through the whole of New Zealand and had the potential to do enormous damage to white clover, a plant that had an estimated financial benefit to farmers of $4 billion annually.

He said pesticides were of no use for control and research was focused on developing either a biocontrol for the weevil or clovers that were tolerant to the weevil, but there would be no quick solution. A parasitic wasp had shown some encouraging signs but general release could be some way off, with concerns being held that it could also destroy helpful native weevils.

Field trials were continuing on clovers but so far no resistant strain had been discovered.

"Farmers have to accept that it could be 10 years or more before research produces an answer to this problem, especially if the level of funding is not increased."

Mr Holmes, who farms 900 cows at Tauhei, said his anger about the issue arose from frustration, a frustration born from being ignored.

"Frankly, I'm pissed off at having to be here today because it shouldn't be our job to advise farmers what is happening, but no one else is doing it."

His message was a simple one: "If you have clover root weevil and you don't do something about it you are going to have 30 per cent less production."

Mr Holmes said many farmers were fooled because the clover was still there, but it was not fixing nitrogen.

"If you find you have weevil, you have to use bagged nitrogen to make up for that loss. Use a little and use it often - all year round."

His annual cost of applying nitrogen was $31,300: "Over 10 years that will be $313,000, but if I did nothing the cost in lost production would be $874,000."

Mr McKie said that put on nitrogen fertiliser twice a week because the alternative was pasture that turned yellow and became useless as feed: "The clover is still there but it will not do the job for you."

Clover root weevil is detectable by U-shaped notches on the leaves of the plant, made by the weevil adult feeding on them. But the larvae are the most damaging, living in the soil and feeding on the stolons, roots and nodules of clover. Once the nodules are damaged the plant loses its ability to fix nitrogen.

- NZPA