It was one of the worst weeds a farmer could find on their property, AgResearch scientist Trevor James told a small group of farmers at a FAR-held velvetleaf information day at Karaka.
“It’s a highly competitive weed and if we can keep it out, it’s going to save the country a heap of money,” James said.
The day was held in a paddock known to have velvetleaf that is the site of a trial testing the viability of growing sorghum on paddocks known to contain the pest plant.
James says it was aimed to provide options for farmers that they knew would work.
Rural Contractors NZ vice-president Helen Slattery says there are now small blocks in Auckland with absentee owners where the paddock was previously in maize that are riddled with velvetleaf.
She says it is imperative people took the risk the plant posed seriously.
No one knows how the plant was able to spread. Velvetleaf seeds are tiny, extremely durable and can lay in the soil for years.
“If the plant is not identified and it’s allowed to go to seed then the seedheads turn black. The astonishing amount of seeds – 30,000 per plant – can stay in the soil for years,” Slattery said.
If one such seed had been in the soil for several years and that soil was then cultivated, it could create conditions for germination.
“This is the danger with this weed. It has a longevity in the soil so it can sit dormant and wait and it can also reduce the crop (yield) by up to 70%,” she said.
Thousands of plants can appear on infested properties particularly after land is cultivated. Seeds can be produced from plants at 15cm tall but plants can grow to 2m.
Stock eating velvetleaf seeds in maize provide a source of spread as seeds are not killed by being digested. Seeds also survive the ensiling process.
Slattery says the best way to stop the plant was identifying and removing the plant before it developed the seedheads.
“The tricky thing with velvetleaf is that it can get to maturity at almost any stage so it can drop seeds at any stage, so if there’s perfect growing (conditions) it will grow as tall as a maize plant,” he said.
Velvetleaf has been declared a pest plant in Waikato Regional Council’s Pest Management Plan, giving the council power to direct and manage it.
Slattery says Auckland Council had not specifically identified velvetleaf as a pest plant, but it was now starting to get to grips with the weed, with several heavy infestations in the region.
The South Island has a different strain of velvetleaf, which produces less seeds and, while still a concern, it appears it is less invasive than the one found in the North Island.
She says contractors should report any velvetleaf and clean machinery between farms, particularly at this time of the year when it presents the most risk of being spread.
“As contractors we have particular concerns because we work on a variety of properties and the last thing we want to do is help spread this pest,” she said.
Waikato Regional Council pest plants team leader Darion Embling says velvetleaf eradication was still a key programme it was involved with since 2016 when there was a major incursion.
That included creating farm plans for farms with velvetleaf and working with groups such as AgResearch on research on how to manage it.
Since then, this containment strategy appeared to be working with no new findings this season so far and two small scale finds last season in Matamata and Otorohanga. The last serious find of velvetleaf was in 2018, he says.
“I think elsewhere in New Zealand, such as Auckland, it’s definitely increasing and it’s a massive risk for Waikato if Auckland can’t come to grips with that,” Embling said.
