Barberry, Nassella Tussock, and Lucerne Weed Control [Field Day]

Driven by the recent discovery of barberry and nassella tussock in several locations within the Hakataramea Valley, the HSC teamed up with Environment Canterbury (ECan) to host an interactive weed field day in June 2023.

The event gathered over 30 attendees, visiting a series of locations to discuss identification and management of these notable weeds. Expand each of the focus topic headings below to read the discussion notes.

Barberry

Barberry is identified as an “Organism of Interest” in the Environment Canterbury Regional Pest Management Plan (RPMP), though it is currently not subject to any rules or a region-wide control program.

The invasive weed is prevalent on Kurow Hill, it is presumed that birds have contributed to the seed spread of barberry into the lower reaches of the Hakataramea Valley. While populations have been identified in locations within the valley, they are still confined to relatively small areas, and control measures will need to be undertaken by landholders to prevent further spread.

Identification

• Barberry can be identified by its spiky, leathery leaves, which become a deeper red in winter making identification easier.

• Established Barberry plants will often be found growing amongst other natives such as Matagouri making quick identification, and access difficult.

Control

• Plants are rubbery inside, making removal by grubbing difficult.

• Metsulfuron has been shown to be good for the control of small barberry plants.

• Burning is not effective as the plants and seeds hibernate, and come away again.

• Experience shows if plants are not killed with the first herbicide spray, it makes it more difficult to kill them on subsequent attempts.

• Some positive results have been found with Tordon™ Brushkiller XT, however, this is only an option for spot spraying.

• Larger plants may be controlled by cutting the main stem and painting with a mixture of Metsulfuron.

• When using any herbicide, read the label thoroughly to ensure all instructions and safety requirements are followed.

  
  

For more information on Barberry, click here

Nassella Tussock

Nassella tussock has been prevalent on the south side of the Waitaki River for some time but test sites and surrounding areas show it is spreading. It has been found on several properties at the lower end of the Hakataramea Valley.

Nassella's initial introduction into the Waitaki district is thought to be in hay transported from areas such as Marlborough. Vigilance is recommended at sites where imported feed has been stored and fed historically.

This invasive tussock spreads quickly and chokes out other plants rendering the ground unusable. It quickly becomes a problem because it is unpalatable to stock, displaces desirable pasture and a single plant can produce thousands of wind-spread seeds which quickly colonise hill country if left uncontrolled.

Identification

• Key characteristics aiding in identification include:

  • generally smaller than other common tussock varieties

  • a distinctive tufted growth habit, with leaves which are darker green and erect when small, but lighter in colour and droopy in grown plants

  • purple flower heads (late October through to January) that are carried on slender stalks, and drop down as they mature

  • leaves feel rough when rubbed from the tip to the base

  • cream-covered stems which are swollen just above ground level – similar to a shallot

  • roots which are deep, fibrous and matted making plants difficult to pull out

• Identification can be assisted using some Plant ID apps such as:

  • iNaturalist

  • Find-a-Pest

• Nassella is difficult to recognise if you aren’t experienced at identifying it. ECan have a handy ute guide available, which can be downloaded and printed by clicking here.

  
  

Control

• Individual plants can be grubbed with success.

• Annual re-checks of the controlled areas are essential to pick up missed and/or regenerating plants.

• Where larger control jobs are required it is suggested to contract a control team such as Vector. These expert control teams are commonly used and make short work of large infestations in extensive country.

Additional comments from the ECan Biosecurity team

• We are currently working with farmers in Duntroon to identify and control Nassella tussock infestations. This work will also look at the effect of cultivating paddocks and using winter crops where there are known Nassella infestations. It is thought that disturbing the ground might slow/stop growth in those cultivated patches. However, there are no definitive results yet.

• We are looking for guidance from farmers to help them plan their next areas for investigation. They are happy to assist by teaching farmers what to look for and how to identify.

• If you are unsure if you have Nassella tussock, contact ECan to report/receive assistance with identification, call 0800 324 636 or email biosecurity@ecan.govt.nz.

• Nassella can be difficult to control, and currently, there are no quick fixes.

Lucerne Weed Management

The next stop for the field day was a lucerne stand on McHenrys Road, where the group heard from Paul Verdonk (PGG Wrightons) about the paddock history before Mike Cox (NuFarm) spoke on recent advancements in herbicides for winter weed control in lucerne stands.

Example paddock - history

• Six-year-old, K-line irrigated lucerne stand on sandy-based soil.

• Drilled twice. High plant population.

• Dandelion, horehound and other ground cover perennial weeds are prevalent.

• Historically sprayed with standard mixes, including Paraquat, Gramoxone and Atrazine. No spray on 3rd year.

• OK to stitch with cocksfoot, fescue or similar towards end of stand’s lifespan (around 7 years).

• Lucerne is still the best option for reliable dryland farm feed.

• Autotoxicity is still an issue when resowing lucerne, therefore recommend spelling paddocks for a few seasons before redrilling with lucerne.

Chemical options

• Metsulfuron is still a good option for winter spray of established lucerne crops, but results in loss of or reduced first cut.

• Hexazinone is a good option for winter spray in established stands without losing first cut, but not guaranteed to kill all weeds. The benefit is the residual capability, so it is important that the chemical can reach the ground in most places. I.e not being impeded by ground covering weeds.

• Gramoxone mixed with a soil residual chemical (e.g. from the Triazine family Atrazine, Nu-Trazine, Sharpen etc..) is good for both soil and foliar residual effects.

• Some farms have reported issues with the Triazine family of chemicals losing effectiveness over time, weeds are beginning to show resistance. Some South Canterbury grass farms are starting to report 100% herbicide resistance, and needing to look elsewhere for weed controls.

• For new stands and its first winter spray Kyte or similar is a good option. However, it does have limitations and a withholding period if stitching lucerne with other pasture, check before use with your Field Rep.

• Chateau herbicide

  • Chateau is a Nufarm product that has just been registered for use in lucerne, its scientific name is Flumioxazine

  • It is a soil residual enzyme inhibitor and can be used for stands of 1yr or older or that have been through a winter, but is still relatively untested on newly planted lucerne.

  • Was previously used in horticulture, and can’t be applied aerially.

  • Best applied after final graze in Autumn/winter.

  • Showing good results for emerging horehound and dandelion, but will not kill older more established weeds. Will be best used on clean lucerne stands with good access to the soil. Can control other weeds such as poa annua, speedwell, mallow etc

  • The herbicide does have some residual effect, and has a withholding period for stock so check before use.

  • Chateau can be tank mixed with Paraquat for better control of broadleaf weeds and grasses.

  • It needs moisture for the seed residual ingredients to be effective, preferably within a month of application.

  • Application rates range between 140-280g in a minimum of 200L/water per hectare.

• Glyphosate on lucerne is generally not recommended as results can be erratic and result in poor productivity. Same as Metsulfuron.

• Chemical prices and availability seem to be stabilising with good supply currently for the upcoming season.

• Approx costs (at time of field day)

  • Atrazine: $50 p/ha,

  • Chateau/Paraquat: $70 p/ha.

  • Check with your local retailer for up-to-date costs.

• There have been studies investigating the banning of Glyphosate, particularly in European countries. Seem to be inconclusive in the findings, nothing to suggest its removal currently.

• There are ongoing investigations into Gramoxone and Chlorpyrifos.

Application timing and management

• Graze prior to spraying for better uptake.

• High rainfall following application will have effect on spray uptakes.

• It is beneficial to do winter lucerne spray. If timed and done correctly as it can increase yields by 20 – 30 %.

• It is best to spray as early as possible once dormancy has started (a few frosts in). Once leaves are starting to colour, the winter spray will lose its effectiveness. If left too late to spray and lucerne has started to bud, you’ll lose productivity and yield.

Other comments

• Dandelion is still an issue with no real solution. Most of the known lucerne sprays will knock but not kill it. Pre/post emergence sprays are still crucial, as new-generation herbicides will still be most effective on clean, low weed paddocks.

OSPRI – Targeting TB

The final part of the day concluded with an overview of OSPRI’s role in TB operations.

• NAIT & TB Free amalgamated to form OSPRI. Their primary roles are education, eradication and monitoring of TB zones throughout NZ.

• Farmers should notify OSPRI of any suspicious findings relating to pests.

• TB risks spread to cattle and deer herds through wild pigs, ferrets and possums.

• Possums are the main form of spread, and the target is to get possum populations below two per hectare.

• TB is a disease that people can catch and is detrimental to our health.

• Without control, pest populations can re-establish quickly. The Cargill area near Dunedin was TB-free in 2015, however, two wild pigs were released in the area resulting in eight infected herds identified within the two-year period that followed.

TB Control

• Monitor possum activity.

• If trapping or shooting, look for lesions under the arm on possums, and under the jaw for pigs.

• Infected pigs aren’t big TB spreaders themselves, however, the risk comes from hunters who may gut animals and dump offal at a different location to where the animal was killed. If offal disposal is not covered, it may be consumed by other animals who will then spread the TB.

• If infected pests are found on the property, doesn’t necessarily mean cattle or deer herds will become infected.

• Once an area is deemed TB-free, OSPRI-funded pest management stops due to funding constraints. It is then up to the community to work together and communicate any findings and/or coordinate pest control activities.

• No pest monitoring is currently planned for the Hakataramea Valley by OSPRI for the next two years.

Thank you...

To conclude the day, some of our local weed and pest control operators were invited to come along and introduce themselves to attendees. As a community, we would like to support our local contractors who undertake the majority of pest control groundwork.

The HSC would like to thank the following people for helping make this field day a successful event Wade & Sally Newlands, Bruce & Christine Nowell, Kennedy Lange, Noel Crump & Matt Smith (ECan), Paul Verdonk (PGG Wrighton), Mike Cox (NuFarm), Ross Chilton (R & R Pest Control), James Horton (OSPRI), Ross & Trish (Kurow Hotel).