Managing blackberries around waterways

By Kate McKenna, Siwan Lovett, Antia Brademann and Leon Miners

Blackberries are widespread weeds in Australia – noxious in all states and territories and listed as a Weed of National Significance. The plant was introduced to Australia in the 1840s for berry production and to control streambank erosion. In 1851, Baron von Mueller, the then Victorian government botanist, envisioned the introduction of the blackberry bush as a way of improving equality of access to fruit year round. Unfortunately, however, we now know the significant consequences of the introduction of blackberry for our natural environment.

There are 16 blackberry species present in Australia, almost all of them originating from Europe, a smaller amount from North America and 1 species native to Australia (this one is not considered a weed and is our native raspberry). Some hybrid species have started to adapt to Australian conditions, making them even trickier to get rid of.

Excerpt sourced from a 1926 newspaper.

Not to be confused with native raspberries!

Introduced blackberries have leaves that are dark green on top with a lighter green underside. Photo Credit: Birgitte Verbeek (NSW DPI).
Native raspberries are easily distinguished by their pinnate leaves and distinctive pink to red flowers. Photo Credit: Birgitte Verbeek (NSW DPI)

Where do blackberries grow?

Blackberries can grow in a large variety of conditions, with the key factor being at least an annual rainfall of 700 millimeters. This range includes almost every altitude on the Australian continent (but they are not known to grow higher than 1995 metres above sea level). Blackberries can grow on the banks of waterways, wetlands, roadsides, pastures, forests, plantations and grasslands.

Blackberries infest large areas very quickly, growing vigorously and smothering native vegetation under its dense canopy. They are predominantly found in the temperate regions of Australia, around Tasmania, Victoria, NSW and South Australia, as well as some parts of Western Australia. Climate modelling indicates that some regions will see a significant increase in presence such as Tasmania and the Alpine regions in South Eastern Australia (more information on climate change modelling can be found on page 13 of the Blackberry Control Manual)

These 2008 maps indicate the current and potential distribution of the R. Fruticosa blackberry in Australia. Although the maps are 13 years old, they still represent the distribution in 2021 as this blackberry species has reached its full climatic potential in Australia.  It is unknown how other blackberry species will spread if they are introduced (as shown in Figure 1.3).

Problems caused by blackberry infestation

Blackberries are an invasive species and negatively impact Australian native ecosystems. They can have a large impact on primary industries making grazing and cropping difficult with large infestations, and can also become a hazard during natural disasters.

Aerial view of a blackberry infestation impacting on farmland. Photo Credit: Richard Snashall.

Some problems caused by blackberry infestations include:

  • They can smother native vegetation under its dense canopy, and large areas can be quickly infested. This can degrade natural environments and reduce native biodiversity.
  • Blackberry infestations can reduce the productivity of primary industries such as grazing, cropping and forestry. This is because the infestations can shade out pastures and crops, compete for soil moisture and nutrients which suppresses productive vegetation and reduces the stock capacity to graze in infested pastures. As well as impacting on production levels/values due to lambs, heavily woolled sheep becoming entangled and perishing.
  • Blackberry bushes can prevent regeneration of natural hardwood forests and can reduce the capacity of both softwood and hardwood seedlings to establish and grow.
  • Infestations can reduce the visual and recreational value of public land, parks and reserves, as well as restrict recreational and agricultural access to land and water. This can be particularly significant for farmers if their stock cannot graze on pastures or access dams as a result of prickly canes. Walking tracks, paddling launch sites and fishing access to streams can also be blocked, restricting recreational use.
  • Blackberries also harbour invasive animals such as rabbits and foxes, who are prone to further dispersing the plant’s seeds when they are carried on their fur or their droppings.
  • Dead leaves and sticks from blackberry bushes can create a fire hazard as they burn easily and can suck moisture out of the soil. Infestations can also obstruct fire trails and access to water sources.
Blackberry growing on the edge of the Murrumbidgee River, NSW. Photo Credit: Antia Brademann
This blackberry infestation blocks a walking track. Photo credit John Hosking (NSW WeedWise)
Blackberry can colonise and smother native vegetation. Photo Credit: Antia Brademann.

Currently, blackberry plants have invaded over 8.8 million hectares of land in Australia, whilst still being primarily restricted to the South-Eastern coast’s climate.

Biology of the blackberry bush

Blackberries have a very distinct life-cycle and biology, which is important to understand in order to control an infestation effectively. Blackberry is a perennial (long plant life expectancy), semi-deciduous (loses significant amounts of yellowing leaves during the cooler months), prickly plant. It can appear as a semi-scrambling or semi-erect shrub, reaching several metres high (especially when growing over other vegetation). The stems (canes) can vary significantly, ranging in colour from green to purple or red. The stems can be smooth or hairy, and round or angled. The plant’s young canes start growing in spring and flower from late November to late February. The fruiting period is from late December to April.

Blackberry forms tall, tangled thickets. Photo credit: Auld & Medd (NSW WeedWise)
Labelled diagram of the Rubus fruiticosus aggregate plant parts. Image Credit: Birgitte Verbeek (NSW WeedWise)

Blackberries have a two-year life-cycle

Year One:

  • In the first year, the plant grows very rapidly and produces a few single leaves along the cane (stem). At this stage the plant does not grow any flowers or fruit.
  • These first-year canes grow in spring and in autumn when their tips touch the ground, the plant sprouts roots and produces a new bud (called daughter plants) that will grow into a new first year cane the next spring. Blackberries can also propagate from seed.

Year Two:

  • In the second year, the plant’s cane grows, allowing more leaves to grow, along with flowers and fruit.
  • After fruiting during the summer/autumn, the second-year cane stops actively growing and leaf yellowing can be seen.
  • Blackberry seed can fall to the ground, or be spread by foraging animals such as foxes, cows and birds and propagate new plants from there.

Blackberries have many characteristics and forms of defence that make them hard to control:

  • Prickly canes that make them difficult to access.
  • A waxy leaf surface that prevents chemical translocation*, which is an essential component of herbicide control methods.
  • The ability to propagate by itself through a number of means and grow in a large range of climatic zones.
  • They have a secondary root system so that when the crown (above ground component of the plant) is under threat (from natural and human threats), the root system creates small buds as a last line of defence. The buds then detach from the primary root system and establish roots in the soil several metres underground. These buds can lay dormant and emerge up to two years after herbicide spraying.
  • Blackberry seeds are easily spread by foraging birds and animals as their fruits are sweet and enticing to wild animals.
A blackberry root system. Photo Credit: Richard Snashall.

*Translocation: transport (a dissolved substance) within an organism, especially in the phloem of a plant, or actively across a cell membrane.

How to control blackberries

Blackberries can be managed through a variety of different methods, including chemical, biological and physical control options. The most appropriate control method will depend on the size and location of blackberry infestations in the landscape. Each species of blackberry responds differently to the control methods, so it is important to know which species you are dealing with. We recommend doing more research on individual species responses in the Blackberry Control Manual (Part 2, page 19).

It is important to note that successful control of blackberry (especially if infestations are large), involves a multi-year process. Factors to be considered when undertaking a control program include:

  • Control early, monitor vegetation regularly.
  • Location (difficult to access sites may require special equipment such as long spray hoses, waterways need appropriate controls that protect aquatic health).
  • Off target vegetation- desirable vegetation should be retained wherever possible.
  • Capacity to control infestations including follow up, sometimes over a number of years.
  • Do you have the right knowledge/training to undertake planned program? If not seek advice and get trained.
  • Land tenure (know your property boundaries and work with your neighbours).
  • Remember that ultimately controlling blackberry is only a means to an end. Part of your control program planning should incorporate replacing or encouraging native or desirable competitive vegetation in place of the blackberry to ultimately improve your farm productivity or health of bushland and waterways.

The video below discusses how to control blackberries, particularly after fire when they can bounce back and really take hold.

The video introduces the different methods you can use to control blackberry, we have provided more details here for those interested in learning more.

Herbicide control

Herbicide spraying can be the most effective form of control for blackberry, however, it is only recommended and legal if you have undergone the correct training, as it can be dangerous to humans and the environment. It can sometimes be an advantage to employ a weed control contractor with the correct qualifications, equipment and experience to control blackberry.

  • The blackberry plant and its leaves need to be actively growing in order to be effectively killed. When leaves start to turn yellow in autumn the plant is no longer growing. Plants should not be sprayed when under stress, such as during very hot days and over dry periods, or if they have yellow limp leaves or extensive rust. It is best if the plant is flowering or has healthy fruit.
  • It is important not to spray on days where the temperature is over 30 degrees C, as this can result in vaporisation and contamination of nearby native plants. Avoid spraying when rain is imminent as most chemicals have a specified period which require them to ‘set’. Rain during this period can reduce efficacy and also cause run-off of chemical on to non-target plants or waterways.
  • The whole plant needs to be treated, especially the leaves, as this is the best place for the chemicals to enter the plant. The herbicide enters through the microscopic openings on the leaf called the stomata, where the plant transpires. Bigger leaves are more effective at absorbing herbicide as they have more openings. When spraying ensure that the leaves are drenched with the chemical, but not so wet that drip occurs.
  • The spray pressure of the hose is important. High pressure hose settings reduce the effectiveness of the chemicals and can actually cause significant harm to surrounding plants and animals. Droplets are more likely to bounce off leaves and damage nearby native plants. This means the hose should be on a light-wide pressure setting. When spraying pressure levels achieving a ‘rainfall’ effect is optimal.
  • Another important consideration is the proximity of the infestation to waterways. Most herbicides are harmful to streams and their flora and fauna so cannot be used near waterways. Ensure you only use chemicals to control blackberry which are registered for use near waterways or otherwise permitted eg via a ‘minor-use’ permit.
  • Use best practice methods to avoid chemical entering the waterway. For example, if the plants are on the streambanks, you will need to stand at the edge of the water to spray away from the stream onto the bank, thereby avoiding over-spray from occurring. Run-off or chemical drip from the plant must be avoided at all costs, so lightly spraying is recommended. This may mean follow up is required, but it will reduce risk of contamination.
  • It is also an important precautionary measure to start downstream and work upstream along the bank avoiding any cumulative effect of accidental drift.

Note: a minor-use permit is issued by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for the use of herbicides (or pesticides) in ways other than is prescribed on the label.

Antia (Upper Murrumbidgee Demonstration Reach Coordinator/Rivers of Carbon) dressed appropriately for spraying as observed by Leon (right, Local Land Services, NSW Gov) and Richard (left, Rivers of Carbon). Photo Credit: Richard Snashall.

Landholders also have a responsibility to erect signage if spraying has occurred near/at fruiting stages especially if blackberry is easily accessible by the public. If you are controlling blackberry along a watercourse, landholders have the responsibility to notify any downstream neighbours who use the water source for domestic or stock use at least 500m from the control area. A weeks notice prior to undertaking any works will allow time for them to pump water.

Spraying blackberries while moving upstream. Photo Credit: Best Management Practice Blackberry Control near Waterways, 2019.
Recommended spraying technique around waterways. Photo Credit: Best Management Practice Blackberry Control near Waterways, 2019.

Follow up post 2 years from knockdown is essential given blackberries root system/growth habits. This allows the plant to produce adult leaf which is essential for adequate uptake of chemicals. This may mean the infestation gets nearly as large as when you first controlled it, but there is no point in spraying juvenile leaf, as this does not allow enough chemical to be taken up by the plant to kill the extensive root system that may be present under the infestation.

Regrowth under controlled canes. Photo Credit: Antia Brademann

There are various herbicides which are registered for the control of blackberry and the rate, timing, mode of application and safety is specified on their label. (See NSW Weed Control handbook- link below).

Herbicides must always be used strictly in accordance with the label specifications. Registration of a herbicide for the use on blackberry does not mean it is necessarily the best choice for your situation and when you plan to undertake control. For example, the time of year in which different herbicides can be applied will vary, with some needing to be applied at flowering stages, others are not be used when ripe/near ripe berries are present, while others can be applied over a longer period. The specific blackberry registered herbicide must, therefore, be matched to the needs of your control program. If you are unsure, get advice on herbicide selection specific to your situation, with which your local council biosecurity officers can assist.

Most herbicides are not registered for use in and near waterways. The only herbicide registered for use on blackberry near waterways are aquatic approved Glyphosate formulations. This herbicide may need multiple applications over time to effectively eliminate infestations.

It is extremely important to get the herbicide mixture right, as not measuring the right quantities can be detrimental to the environment, especially to waterways. Please note that in all cases the rates given on the product label are exact and mixing higher rates than specified can actually reduce the effectiveness of the chemical as well as unnecessarily pollute the environment.

It is essential that you only mix enough herbicide mixture for one days work, as leaving the mixture could result in reduction of efficacy. Also make sure spray equipment is thoroughly cleaned (with recommended cleaning agent- see NSW weed control handbook) between using different chemicals.

The Snowy Monaro Regional Council has obtained a minor use permit for the use of Metsulfuron Methyl and Roundup Biactive (or other aquatic approved Glyphosate formulation) in aquatic situations. This permit allows off label use of these herbicides and has provided a more effective option to control blackberry in the Snowy Monaro Regional Council area. This APMVA Permit (PER83324) can be used by employees and contractors employed by the Snowy Monaro Regional Council, South East Local Land Services, Landcare groups and local weeds groups, who are trained and experienced in the preparation and use of agricultural chemicals and under the direction of the permit holder.

This permit is being applied through a blackberry program run in partnership with Snowy Monaro Regional Council, Local Land Services, the Upper Murrumbidgee Demonstration Reach, Rivers of Carbon and local landholders working together to control blackberry along the upper Murrumbidgee River. The program has been a great success, with elimination of blackberry and regeneration of native riparian vegetation now occurring at intervention sites. The success is due to a combination of using the right chemical, experienced contractors and a control program where follow up two years post knockdown and ongoing monitoring is integrated. By working with multiple landholders along the river, this program demonstrates the value of strategic weed control where all stakeholders are working together for landscape scale outcomes.

Wetting agents and penetrants reduce the surface tension of the spray droplet. This means the herbicide sticks to a greater area of the plant leaf instead of running straight off the leaf. Penetrants force the leaf stomata open, allowing the herbicide to enter even when the plant is not transpiring. Wetting agents that have a vegetable oil base are better for the local ecology as they are biodegradable and have lower environmental toxicity, even though organosilicane penetrants are more effective. It is recommended to only use organosilicane penetrant at a large distance from waterways as it can have a significant negative impact on aquatic fauna. Wetters are generally not registered for use in waterways.

Photo: Herbicide spraying of blackberry near the Murrumbidgee River, Bumbalong Valley, NSW. Photo Credit: Richard Snashall.

Herbicide dyes
The advantage of using herbicide dyes is that they allow you to see what you have sprayed and therefore reducing over-spraying and accidental spraying into water or on plants you do not want affected. Please be aware that some dyes may be toxic to aquatic organisms and hence care needs to be taken to ensure they are not allowed to enter waterways.

Fire treatment (not recommended)
Fire treatment, like slashing or burning prior to herbicide spraying, is actually detrimental to the effectiveness of the treatment. It puts the plants under stress which decreases the leaf surface area and results in the plant absorbing less chemicals. The blackberry plant can resist complete elimination even after fire treatment, as the root system digs deeper into the ground. It is not legal to carry out a burn near waterways.

This photo was taken shortly after bushfires ravaged this property. Photo Credit: Richard Snashall.
The same property showing the regrowth of blackberry. Photo Credit: Richard Snashall.

Bushfires create a disturbance event which can decimate favourable and competitive native vegetation and allow existing blackberry to regenerate vigorously and new infestations to establish. On the other hand, there may be better access post fire event and it may be a good time to intervene to control blackberry.

Biological control
Blackberry leaf rust fungus is a form of biological control. It is only effective on European species of blackberry plants. The fungus primarily attacks the leaves of blackberry bushes and causes the leaves to fall off. This causes the plant to die back and prevents any further daughter buds from forming at the end of stems. The rust also extracts nutrients and water from the plant’s cells, reducing its ability to grow and reproduce. The rust grows best in humid conditions, and when the blackberry is actively growing. Ultimately, the rust doesn’t completely eradicate blackberry infestation, but it is useful in areas where access is limited and spraying is difficult due to the size of the infestation. The rust reduces the extent of the bush, allowing sunlight to reach the ground. This permits other vegetation to establish.

Blackberry leaf rust fungus. Heavily infected leaves turn brown, shrivel and fall from the canes. Photo credit: CSIRO Entomology.

Biological control and herbicide control cannot be used together effectively, as the rust reduces the uptake of herbicide treatment. Biological control should only be used with large widespread, inaccessible infestations or where other management options are not viable.

Grazing by goats and other livestock is another proven method for managing blackberry infestation. This approach requires appropriate fencing to contain the goats, especially if it is around riparian areas. Goats can also consume other non-target plants and can destroy native vegetation, which is a highly important consideration if this method is used. As the blackberry is not killed by this method, repeated treatment must be applied in a strategic way to repeatedly graze the plant until its energy stores are exhausted and cannot regenerate.

Slashing could be used to reduce the size of bushes, however will not effectively kill the plant.

Grubbing involves physically controlling plants by digging out the crown of the plant. It is a good method for controlling small plants using hand tools. Large scale disturbance in riparian zones needs to be avoided. Soil disturbance could encourage other weeds so post control monitoring should be applied.

Aerial photo of the Mururmbidgee River corridor at Bumbalong which was impacted by bushfire in early 2020. The Rivers of Carbon team is working together with landholders to control blackberry along the corridor as part of regional bushfire recovery efforts. Photo Credit: Richard Snashall.

Summary: why we need to control blackberries in riparian zones

In riparian zones, blackberries smother other vegetation which stops the growth of groundcover, under its thickets. This means that the diverse native mix of grasses, reeds, shrubs and trees is unable to establish, with negative ‘knock-on’ effects being a loss of habitat and food for riverbank and in-stream biota.

During big flood events, the soil becomes highly vulnerable to erosion, having an opposite effect to its original reason for being introduced in the 1800s which was to reduce streambank erosion. The increased erosion risk is caused by the blackberry bushes smothering out native groundcover vegetation, leaving the soil underneath bare. It is an important consideration when controlling dense infestations to ensure groundcover is replaced as soon as possible to prevent erosion.

Infestations can also harbour pest animal species, and reduce the habitat of native wildlife in riparian areas.

This is why controlling blackberry infestation around waterways is essential, and must be carefully managed to avoid degrading its surrounding vegetation or streams. Through our Rivers of Carbon Program we can help landholders who want to control blackberry, similar programs are also offered by your local Natural Resources Management Agency.

This guide was created by Kate McKenna, Siwan Lovett, Antia Brademann and Leon Miners with funding from the South-East Bushfire Recovery Program