But in the interim affected farmers are being urged to develop a farm management plan to curb its spread.
Funding from industry has enabled the first year of the project but an application has been made to the Ministry for Primary Industries Sustainable Farming Fund to pay for three more years of research into controlling the weed.
It has been estimated the total cost of the project could be $1 million.
Velvet leaf was discovered last year in contaminated fodder beet seed imported from Europe.
Five varieties imported this year had been subjected to a new, more rigorous quality control process, seed importer DLF Seeds general manager Tom Bruynel said.
“We have now had all lines tested in an MPI-accredited laboratory.
“Each line has tested 50,000 seeds and all of them have tested negative to any regulated weed.”
Foundation for Arable Research business relationship manager Ivan Lawrie said new control measures for residual weeds would not be available for some time but farmers could lessen its impact through management.
Lawrie urged farmers who had weed outbreaks last year and who hadn’t done so to contact MPI or FAR to establish farm management plans.
Those plans would recommend crop options for infested paddocks and the right type of tillage so velvet leaf seed was not buried too deep, where it could sit dormant for decades.
Other velvet leaf control steps included sowing crops in infected ground which could be treated with a broad leaf herbicide or were not too tall for machinery to access.
Using machinery and grazing cattle on infected land were potentially seed-spreading risks.
Lawrie said farmers appeared to still have confidence in fodder beat.
“In general, from the conversations I have had with seed companies, it is more or less static.”
New infestations were likely to appear this year because an infected seed line was identified too late last season for action to be taken.
AgResearch senior scientist Trevor James said sites in Waikato and Canterbury where the weed had been detected would be studied to determine as much information as they could about its behaviour and its residual effect on paddocks.
For the following three years the trial would look at proof of concept for larger and more complicated management plans for the weed such as crop options, crop rotations and herbicide use.
Most information on velvet leaf came from the United States and Europe and James said in the US it predominantly grew in maize crops where it was relatively easily controlled with herbicide.
But it was a greater problem with fewer control options when growers switched to soya bean or cotton.
In Europe velvet leaf was moving rapidly from south to north and in Croatia the infested area had grown from a few thousand hectares to about 30,000ha in five years.
Last year’s response had lessened the level of grief among NZ farmers.
“Whether ultimately we get on top of it, it is too early to tell but the steps and means we have taken already have saved farmers a lot of grief.”
It was crucial that velvet leaf was prevented from infecting high-value export crops or markets could be closed or access require more screening and inspection adding to cost.
Bruynel said most imported fodder beet seed this year came from Italy with some from France and the test results showed MPI’s and his company’s new clearance system was working.
“I am satisfied all the work done in the fields of Italy and France and at the processing plant in Denmark has done what is required and that is to produce high quality seed that is at a very high level of purity.”
