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Velvetleaf, which is spread by machinery or contaminated maize, is currently found on 105 properties in nine regions of the North Island: 61 in the Waikato, 20 in Auckland, 15 in Manawatū-Whanganui, three in Hawke's Bay, two in Wellington, and one each in Northland, Taranaki, Gisborne and Bay of Plenty.
North Island Velvetleaf Coordinator Sally Linton, who is employed on behalf of the North Island regional councils, Auckland Council and the Foundation for Arable Research, says the issue is that farmers buy maize from all over the country and even internationally, often sight unseen, and contractors who harvest crops often work multiple properties across large areas.
“It’s so invasive that if your neighbour has it and you are sharing equipment then you’re likely to get it if that machine is not cleaned.
“To be honest, no farmer that crops is free from risk – and that is the message we need to get out. Biosecurity starts at the gate. It’ll save you a lot of headaches.”
Velvetleaf was first found in New Zealand in the early 2000s, with infestations of the cropping weed mostly concentrated around Auckland and Waikato.
Overseas, velvetleaf has been reported as causing an up to 70 per cent reduction in crop yields by outcompeting crops for nutrients, space and water.
Linton says velvetleaf is a problem for farmers as it matures as it gets a woody stem that becomes resistant to many herbicides and normal weed management practices. Also, its seeds (up to 33,000 seeds per plant) can lie dormant in the soil for up to 50 years – springing into life in response to cultivation and movement of soil.
“The discovery of velvetleaf on a property can significantly impact farming businesses as cropping is difficult and more costly,” says she says.
“So, while there are rules to prevent its spread from properties, we also do everything we can to support landowners who are affected.”
Landowners are responsible for destroying velvetleaf, which is an unwanted organism under the Biosecurity Act, and all machinery leaving an infested property must be cleaned.
“We work closely with the owners and managers to develop a biosecurity farm management plan for them, and we also talk to the cropping industry, in particular, to remind them of the ongoing risk of velvetleaf to our regions and the importance of good hygiene practices.
“Landowners should do themselves a favour when purchasing maize to check the crop in case it is contaminated, and, likewise, contractors should understand the biosecurity risks of the crops they’ve been asked to harvest and have a plan in place for managing weeds such as velvetleaf.”
Linton says a significant amount of work has gone into controlling velvetleaf by regional councils since it was first discovered.
“A big focus is the tracing of machinery and crop movement, so we can establish and mitigate the source of spread.”
Suspected sightings of velvetleaf should be reported to your regional council or Sally Linton sally.linton.nz@gmail. com.
About Velvetleaf
Velvetleaf is an annual broad-leaved herb that grows between one and 2.5 metres tall.
Seedlings are vigorous and the plant grows rapidly in the first few months after germination.
It has buttery-yellow flowers, about three centimetres across, from spring through to autumn. Leaves are large, heart-shaped and are velvety to the touch.
