Despite its rather pretty name, there is nothing desirable about the weed velvetleaf, Abutilon theophrasti, commonly known as Velvetleaf.

This member of the mallow family is notoriously hard to destroy, and if left to spread will have devastating consequences on New Zealand’s arable farming industry, according to AgResearch senior scientist Trevor James.

He’s heading the Velvetleaf Action Group, which was formed in July 2018 using a $579,000 grant from The Sustainable Farming Fund, to complete three years of research.

Velvetleaf is fast-growing, and can quickly overshadow crops – some of which can’t tolerate a late herbicide application, says Trevor.

“Each plant can produce 20,000 seeds, which survive passing through animals, and can lay dormant in soil for more than 50 years,” says Trevor.

Trevor’s team has adopted a two-pronged approach for understanding the plant. “Firstly, we are growing plants in secure, contained areas at five locations across the country,” says Trevor.

This will determine, among other things, how far South it can grow and its tolerance to drought.

“Secondly, we are looking at alternative crops, such as cereals, where late herbicides can be used, and it’s easier to find plants that have been missed,” says Trevor.

Council on board

Velvetleaf has been declared a pest plant in Waikato Regional Council’s Pest Management Plan, giving the council power to direct and manage it.

WRC team leader for pest plants, Darion Embling, works with farmers to implement a Farm Management Plan on infected farms. Currently, there are 53 infected farms in the Waikato and one in the Bay of Plenty.

“If nothing is done and the plant establishes in New Zealand, we are looking at a 30 per cent loss to the arable industry, and we will be unable to grow maize on these farms,” says Darion.

“Once the land is infected, it can no longer grow maize, and other uses must be found for it, along with continued monitoring for velvetleaf,” says Darion.

Farmers are advised to check crops early, pre-Christmas, and adopt pre-emergent and post-emergent herbicide spraying.

Darion says maize is the biggest risk to velvetleaf establishing – because if not caught early enough, when the crop is young and low, it can grow to maturity hidden in 3m high maize, flower and go to seed.

It can then be passed from farm-to-farm on machinery used to cut maize, or travel in maize silage sold to other farms.

“We have had a very good response from most farmers, and some very positive results,” says Darion.

“Each farmer is responsible for reporting velvetleaf on their farm, and procedures for cleaning machinery that enters and leaves their farm are paramount.”

Darion hopes the Waikato infestation has been contained. And he says a robust forward tracing system is in place, with a farm confirmed as having velvetleaf sees farms that received maize silage from it, or were visited by the contractor’s machinery next, are monitored.

Bringing in experience

Consultant agronomist, with previous roles at the Foundation of Arable Research, Mike Parker, has more than 40 years’ hands-on industry experience.

He’s been contracted to WRC to work with farmers and carry out farm inspections at identified at risk properties. “I pay particular attention to around the cowsheds, silage stacks, gateways, sidelands and headlands of the maize paddocks,” says Mike.

Plants are pulled by hand, unless they have already formed seed heads. These are carefully covered in plastic bags and contained before pulling. Plants are incinerated to destroy seeds.

Mike says many preventative steps can be taken on-farm that will not only deter velvetleaf from establishing, but also other invasive weeds.

Particular attention can be paid to the headlands where machinery has turned the most. “I recommend that all sidelands and headlands are sprayed with a pre-emergent herbicide including the active ingredient saflufenacil (Sharpen).

“Later, the headlands should be sprayed with post-emergent herbicide including the active ingredient topromezone (Arietta),” says Mike.

Weed management practices

He also suggests when farmers spray out grass paddocks, they leave a half-metre buffer at the fenceline and let the grass take over, eliminating bare land that will not be planted, and be open for weeds to establish.

“It’s the little details in weed management practices that can make a huge difference. We need to take biosecurity much more seriously,” says Mike.

Trevor says they need people to be really astute, for contractors to be trained “and for farmers to be our eyes”.

Rural Contractors New Zealand vice president Helen Slattery, who is Waikato-based, is RCNZ’s lead on combatting velvetleaf.

“Our members travel from farm-to-farm so we’re working closely with the Ministry for Primary Industries, Federated Farmers and councils to maintain our ‘Keep it Clean’ machinery hygiene guidelines. We all need to work together to combat this pest.”

Images of unidentified plants can be sent to Waikato Regional Council, Foundation of Arable Research or AgResearch for formal identification.