Chilean Needle Grass in Marlborough
Managing the invasive weed on sheep and beef farms with the Marlborough District Council
Chilean needle grass can reduce stock carrying capacity, income and potentially, property values. Seeds attach themselves to people, vehicles and animals and can also be spread in feed and soil. Their sharp tip and twisting awn may drill through animals’ pelts and lambs’ eyes, causing suffering and potential downgrading of carcasses. This perennial pest plant’s seed heads are a reddish purple in the early summer flowering season but the rest of the year, it looks like any other grass.
In Marlborough, Chilean needle grass grows on 158 properties across 2803ha, concentrated in Blind River south of Seddon. The area continues to grow, with infestations found on eight new properties in 2014-15. In Hawke’s Bay, Chilean needle grass is found on about 130 properties distributed across approximately 550 hectares. It is identified on about four new properties a year.
Chilean needle grass was first found in North Canterbury in 2008. For two years, infestations in the Cheviot area of Canterbury had been static, at 320ha on 14 properties but a new site was found at West Melton near Christchurch in the 2015-16 summer.
The pest plant has the potential to spread into up to 15 million hectares of dry hill country throughout New Zealand. To prevent this happening, affected land managers must contain spread and those without it, practise good farm biosecurity.
The registration of sodium flupropanate, branded as Taskforce, in 2011 revolutionised control of Chilean needle grass and closely related nassella tussock. The herbicide leaves a residue in the soil which kills germinating seeds but also makes it difficult to establish pastures after control. There is a 120-day stand-down between aerial spraying with Taskforce and grazing stock and 14 days after spot or boom spraying. Also, stock must be held on clean ground for 14 days before slaughter.
Tim Struthers is among Marlborough farmers getting good results from a three to four-year cycle with Chilean needle grass that was “pretty much everywhere” to permanent pasture. For 20 years, Tim’s been managing a farm and vineyard at Blind River, the core area for this invasive weed in Marlborough. The success of the control programme has given him the confidence to buy land in the area including much of the property he’s been managing and a share in a vineyard.
Learning as he goes, it’s taken almost five years to transform land abandoned to Chilean needle grass into productive permanent pasture, says Tim. With what he knows today, he believes the job could be done in three years.
The breakthrough came with registration of sodium flupropanate – branded as Taskforce, in 2011. In June 2012, that was extended to aerial application. Pre-Taskforce, Tim merely sprayed a 10-metre strip around the 100ha property with glyphosate herbicide to meet Marlborough District Council requirements to prevent Chilean needle grass spread. All efforts were focused on growing quality wine-grapes in 15ha of vineyard.
The day Taskforce was registered for aerial use, a helicopter was brought in to spray 50 hectares of solid needle grass on hill country surrounding the vineyard. For two years the Marlborough District Council has been covering the cost of chemicasl in the core Blind River area with landowners paying for the helicopter. “That’s given us the opportunity to do a heap more,” says Tim. Each year he aims to aerially spray 20-30ha. So far 80ha of land has been treated plus 40ha, since sold. For three months after spraying, no stock can be run and the chemical knocks the ground around for much longer, says Tim.
For farmers who relied on livestock for an income, shutting down grazing made life extremely difficult, he said. He’d been fortunate in that the vineyard kept income flowing and propped up the cost of Chilean needle grass control.
Traditional ryegrass pastures are extremely susceptible to this residual herbicide and finding species to replace sprayed-out paddocks has been a challenge. “Working out what to plant has been trial and error,” says Tim. “Brassicas worked, barley worked, as did green-feed oats, rye corn and this year I’ve had some success with plantain after cropping paddocks through the winter period.”
Tim’s worked out that a successful control programme starts with spraying paddocks in late summer rather than the recommended winter, then fallowing for three months. In autumn a winter grazing crop is sown such as brassicas or barley. After a second summer fallow, permanent pasture species are drilled into the soil.
A cocksfoot-lucerne mix was likely to suit, being extremely tolerant to drought and able to outcompete Chilean needle grass, said Tim. Other possibilities included chicory, prairie grass and bromes.
“Dairy grazing through winter has been the key,” he says. “Paddocks are very lightly stocked by the spring-summer fallow.” Now that pastures are established, dairy heifers are grazed from February to end of July the following year and Tim is considering adding bull beef to the mix.
Sheep were grazed through winter, well outside the Chilean needle grass flowering season, and sold straight to the works to eliminate any risk of spread.
Taskforce is not registered for use in vineyards and trials suggest that applied around the base of vines it checks vine growth and vigour, plus residues have been picked up in wines. “All you can do is minimise spread,” says Tim. However, Taskforce is used on headlands where there is a lot of machinery movement and vineyard contractors park.
Chemical topping using light rates of glyphosate (Roundup) in the inter-row area was tried but stopped, to minimise spraying in the vineyard and to conserve valuable time. Instead, the grass is mowed down whenever it looks likely to start seeding, from late spring into summer.
During development of a new vineyard, ground between the vines was sprayed with Roundup then winter-active grasses drilled in winter. Sheep graze here outside the seeding period and the odd plant that comes up is hand-sprayed.
Signs warn people coming onto the farm and vineyard that this is a Chilean needle grass area. Vehicles are cleaned at a washdown before leaving the property, including grape harvesters before and after harvesting crops. Washdown wastewater is spread onto gravel where any Chilean needle grass plants which do come up can be quickly controlled. Another precaution has been employing the same contractor and crew for seven years. “Restrictions on vehicles entering and leaving affected vineyards is certainly a problem for growers”, says Tim.
Chilean needle grass has opened opportunities for Tim to buy small blocks of infested land and amalgamate them, converting them to early finishing country. “It’s the devil I know,” he says. “But if I knew nothing about it, I’d keep driving.”
He is a member of a Chilean Needle Grass Action Group, set up two years ago to educate people about the pest plant after public pressure. Disappointingly, mostly hard-core farmers with Chilean needle grass turned up at meetings, Tim said. These people already knew that shifting stock to other properties was a no-no, yet especially with the amount of vineyard grazing done in Marlborough, those without this serious weed posed the greatest risk.
Seed lasts in the ground for about 10 years so the lag stage between seed movement and establishment means new infestations can be easily missed.
Marlborough District Council biosecurity coordinator, Jono Underwood, says Chilean needle grass has been a problem in the district for decades. Infestations have reached an exponential stage where the pest plants are being picked up in more places more frequently. The major threat was to pastoral hill country, he said. If the plant spread across country which could not be accessed by ground-based machinery, management became 10 times more difficult.
Awareness was growing, amongst those with no experience of the weed, he said. This was due to a concerted effort by the Marlborough District Council, Hawke’s Bay Regional Council and Environment Canterbury, with support from Government’s Sustainable Farming Fund. People were being taught how to identify Chilean needle grass during flowering and how to keep it away from their front gate. The plant’s long-living seed meant new infestations might not become obvious for five to 10 years.
When a new patch is discovered, the Marlborough District Council staff gets in early with Taskforce then scours the area intensively for several years. On the 70 or so properties where infestations are long-standing, the Council provides Taskforce chemical to kill plants and backup advice.
For people who do have Chilean needle grass, the emphasis is on management using Taskforce to kill the weed on farmland then known pasture establishment techniques to return land to production.
In summer-dry areas, Jono recommends applying Taskforce when pastures are dried out and dormant. Forage crops such as brassica, rape or winter barley could be direct-drilled in autumn, after at least 100mm of rain to ensure soil residue was safe for re-sowing. Following a summer fallow or crop, permanent pastures could be sown the subsequent autumn including cocksfoot – expensive and hard to establish but Taskforce-tolerant. In tractor-accessible areas lucerne was a good option, Jono said. While lucerne and also clover growth could be checked in year two as Taskforce reached their main root zone, plants later recovered.
Follow-up spraying with grass-specific herbicides which was common practice, helped supress grass weeds including Chilean needle grass.
Farmers who opted not to sow following treatment were letting soft grazing bromes and danthonia come through, although broadleaf weeds and thistles were also prevalent, Mr Underwood said.
Once pastures were returned to production, lurking Chilean needle grass should be controlled by spot spraying.
This advice is backed by early results of an AgResearch study confirming that ryegrass species especially were susceptible to Taskforce but certain forage and pasture species were not affected.
In vineyards, the risk of spread was high due to the large number of people, vehicles and machinery entering and leaving. Yet with Taskforce not registered for use in vineyards, options were limited, said Jono. All that could be done was to encourage practices which avoided movement of seed to new areas. The main tools were glyphosate herbicide between rows and inter-row crops, he said.
A sturdy Chilean Needle Grass Ute Guide is available from firstname.lastname@example.org 03 314 8014
Do you suspect you might have found Chilean needle grass or bought in contaminated stock, feed or seed? If so, urgently contact:
Environment Canterbury 0800 324 636 ecan.govt.nz
Marlborough District Council 03 520 7400 marlborough.govt.nz
Hawke’s Bay Regional Council 0800 108 838 hbrc.govt.nz
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