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September’s Weed of the Month!

By on September 2, 2016 in Weed-of-the-Month

Its September, and that means its time for a new Weed of the Month! We are working with our partners at the Columbia Gorge Cooperative Weed Management Area to promote invasive knotweeds  (Fallopia sp.) as our weed-of-the-month for September. Knotweed is a horribly invasive plant unleashed on the countryside by well-intentioned gardeners attracted to its […]

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BMP: HIMALAYAN BLACKBERRY (Rubus bifrons)

Common name:

Himalayan Blackberry, Armenian Blackberry

Scientific Name:

Rubus bifrons (syns. Rubus armeniacus, Rubus discolor, Rubus procerus)

Noxious Weed Listing:

Description:

General:

Himalayan Blackberry is a tall semi-woody shrub, characterized by thorny stems and edible fruits.  It grows upright on open ground, and will climb over and trail over other vegetation.  Mature plants can reach 15 feet in height. The canes of Himalayan blackberry can reach lengths of 40 feet and are typically green to deep red in color.  Himalayan blackberry forms dense, nearly impenetrable thickets.  In some instance canes can reach densities of more than 500 canes per square yard.  The canes of Himalayan blackberry typically last only three years before dying off, so dense thickets are often dominated by old canes.

Leaves:

The leaves of Himalayan blackberry are palmate and compound consisting of three to five leaflets.  The leaflets are dark green and fleshy and serrated along their margin.  The underside of the leaves are white in appearance and are covered by minute hairs. A row of small thorns also grows along the underside of the central vein of the leaf.

Flowers

The flowers are five petaled and are white to pink in coloration.  The stamens and ovaries are abundant.  Plants flower from April to August in our area.

Fruits

Fruits develop as green drupe-like berries that ripen into dark purple to black berries in summer.  The fruits are edible up to an inch in length, and widely consumed by wildlife and foragers.

Roots

The Himalayan blackberry plants form enlarged root crowns with numerous buds that develop into new canes.  The also have lateral roots that can reach 30 feet in length and extend 2-3 feet deep.

Reproduction:

Himalayan blackberry reproduces both by seed and vegetatively.  The berries produced are favored by many bird and mammal species, and the seeds can be deposited great distances from parent plants.  Many of the seeds may remain dormant in the soil for several years after dispersal.  Once a plant becomes established, it spreads locally through expanding roots and rhizomes.  The canes of adult blackberry plants will also root at the nodes to form daughter plants along its margin.

Habitat:

The areas most infested by Himalayan blackberry are disturbed sites and along stream corridors.  Blackberry flourishes on open ground, and on unmanaged sites.  Plants grown in wet soils tend to be dense and more robust.  Due to the movement by birds, Himalayan blackberry also is commonly found under perching sites, such as along fence rows and under power lines.

Impacts:

  • Himalayan blackberry is a highly invasive plant that replaces native vegetation.
  • The canes of blackberry can build up substantial litter layer which may serve as fuels for wildfire.
  • The thorns of the blackberry plants can limit the access of a site by both animals and people.
  • While dense thickets can be useful to some wildlife species, the diversity of habitats is greatly diminished, thereby diminishing the usability of a site to only a few species.

Introduction:

The first herbarium record for Himalayan Blackberry in Oregon was collected in Marion County in 1922 (Oregon Flora, 2013).  The original introduction of Himalayan blackberry to Oregon is believed to have occurred between 1875 and 1899, but was first noted in our area in 1903.  By 1920 it was considered widespread throughout the Willamette Valley (Christy et al., 2009).

Distribution:

Clackamas County:

Himalayan Blackberry can be found throughout Clackamas County.  It is very widespread and directly impacts properties throughout the county.  As an ubiquitous weed this is not a species that is actively surveyed and the mapped distributions do not represent the full extent of the Himalayan blackberry population in Clackamas County.

State of Oregon:

United States:

Management:

Strategy:

The management of invasive weeds is best served through a process know as Integrated Pest Management (IPM).  IPM is a weed management methodology that utilizes:
  • Management thresholds to determine when and if to initiate control,
  • The ecology and life history characteristics of the targeted invasive weed,
  • Site specific conditions and land use considerations to inform management practices,
  • The effectiveness and efficiency of various control methods.
An IPM based strategy ensures the maximum effectiveness of treatment measures.  IPM strategies typically use more than one management method to target one or more susceptible life stages.  It is adaptive to site conditions in the field and to the response of a plant to management.  The utilization of multiple management tools also inherently reduces the use of herbicides in a management plan.   The IPM process ultimately provides a framework for the establishment of Best Management Practices (BMP) which outlines the best approach for controlling a weed particular infestation.

Considerations:

Before implementing weed control activities on your property it is important to consider the potential impact of your planned treatment.  Take the time to consider how your planned treatment activities will impact:
  • Animals-Recognize that treatment activities can negatively impact animals.  Plan your weed treatments to provide corridors and refuge to animals whenever possible.  Make a plan for reconnecting wildlife to your area after treatment.
  • Birds - Survey your treatment area for bird species and avoid treatments during nesting periods (Feb-Aug) or when fruiting to minimize the impact to bird species.
  • Beneficial insects and pollinators - Avoid treatments when plants are blooming to minimize the impact to native pollinators.  Also plan treatments during cooler weather when insects are less active.
  • Native plants- Target weeds during the times of the year when native plants are dormant to minimize the impact to native trees and shrubs.  Use targeted weed control practices to only target invasive weeds
  • Soil erosion- Recognize the potential for your site to erode.  Be especially aware if working on sloped sites, as these tend to be more highly erodible.  Weed control practices will routinely result in bare ground, so have a replant strategy ready following treatment to maintain your soils.

Manual:

The control of Himalayan blackberry can be a difficult task.  The sharp thorns and dense thickets formed by Himalayan blackberry inhibit movement and complicate control efforts. Himalayan blackberry thorns easily penetrate woven fabrics, and thus, thick leather gloves, long shirts, and thick pants are recommended when working with blackberry. Manual removal of Himalayan blackberry can be an effective control option, but it is labor intensive and often a difficult and painful process.  Small seedlings can be easily pulled with thick gloves, but mature plants are not easily removed.  The dense thickets formed by blackberry greatly limit access.  A site can be made more accessible for manual removal by using a long board or sheets of plywood to mash blackberry canes down to the ground. Plants can then be cut at ground level using loppers, machetes, or saws.  Once cut, root crowns and large lateral roots can be grubbed out using a Pulaski, a mattock, shovel, or Shrub Buster.  It is important to remove as much of the root mass as possible to prevent resprouting.  While effective, this process heavily disturbs soils and increases the erosion potential of a site.  Therefore, this is not recommended on steep or unstable soils. While manual removal can be an effective treatment, it requires diligence to be effective.  A site will need regular follow-up to remove resprouts and seedlings.  A large number of seeds can persist in the soil under dense stands, so expect repeated efforts, as you exhaust the seed left in the soil. Cutting alone can be a useful management tool to prevent seeding and to allow access to a site.  Unless repeated regularly and over several years,  cutting alone will not eliminate blackberry.  Blackberry plants will readily resprout following cutting from below ground root crowns.  Cutting is best used in combination with removal of root crowns and large lateral roots, or a targeted herbicide application to prevent resprouting.

Mechanical:

Large infestations of Himalayan blackberry can be removed through brush-mowing.  Like cutting, brush mowing alone won't kill Himalayan blackberry.  Mowing must be repeated at regular intervals to exhaust carbohydrates stored in underground roots.  Due to the thick growth of blackberry, mechanical removal can be very effective at increasing the access of a site to allow for crown and root removal, herbicide application, and replanting. Tillage can also be an effective for removing blackberry root crowns.  Crowns and canes should be raked up and removed following tillage to prevent resprouting.  Tillage causes extensive soil disturbance, so it is generally not recommended, unless a site is undergoing renovation.  Blackberry can resprout from small root fragments, so follow-up should be carried out to target regrowth.

Cultural:

Burning can be an effective tool to clear large dense stands, but it will not eliminate Himalayan blackberry.  Other management such as crown removal or herbicide application is required to achieve control.  The available fuels in dense blackberry thickets can also be substantial, so care needs to be taken to keep fire contained.  As such fire is generally not a recommended control measure.  You should check with your local Fire District or the Oregon Department of Forestry for rules and recommendations. Grazing can be an effective method for controlling blackberry.  Unfortunately, grazing animals generally also target other plants as well, so their use is only recommended when blackberries are the dominant vegetation.  Browsing grazers such as goats and sheep are best for controlling blackberry.  These grazers feed best on new growth, and target the leaves, while the blackberry canes remain relatively undisturbed.  Due to the grazing habits of browsing grazers, dense blackberry stands are best controlled by "flash grazing" as site with a large numbers of animals in a small area for a short period of time.

Chemical:

Due to the difficulties associated with controlling Himalayan blackberry, herbicides are often a component in management of this species.  Himalayan blackberry is susceptible to several systemic herbicides.  Young canes are most susceptible, but should only be targeted after reaching at least 3 feet in height to allow the herbicide to be drawn down into its root system.  Plants should not be cut or removed for at least two weeks following an herbicide application.

Before you Start:

  • Before purchasing any herbicide product it is important to read the label.  The label is the Law.  Carefully review all parts of the label even if you have used the product before.  Select a product that is most appropriate for your site.  If you have questions, ask your vendor before purchasing a product.
  • When selecting herbicides always use a product appropriately labeled for your site. Follow label recommendations and restrictions at all times.  If any information provided here contradicts the label, the label takes precedence.  Always follow the label!
  • Protect yourself.  Always wear the recommended protective clothing identified on your label and shower after use.
  • When applying herbicides use spot spray techniques whenever possible to avoid harming non-target plants.
  • Do not apply during windy or breezy conditions that may result in drift to non-target plants
  • Avoid spraying near water.  Hand-pull in these areas, to protect aquatic and riparian plants and wildlife.
  • Avoid exposure to pets, pollinators, and wildlife.  Remove animals from treatment areas to avoid exposure to herbicides. Follow the reentry instructions on your herbicide label and keep pets out of the area until the herbicides have dried.  Avoid spraying when insects and animals are active.  Avoid spraying blooming plants to minimize an effects to bees and pollinators.
  • Be sure to store any chemicals, out of the reach of children and pets to keep your family safe.
  • Product labels and formulations change regularly.  Check the Pacific Northwest Weed Management Handbook and the label for current control recommendations.

Herbicides:

The mention of any brand name product is not, and should not be construed as an endorsement for that product.  They are included here only for educational purposes.  Suggested rates are generalized by active ingredient.  Specific rates will vary between products.  Be sure to review the label before application and use the recommended label rate at all times.

Active Ingredients

Product Names: Accord, Aquamaster, Rodeo, Roundup, and various others Rate: Broadcast: 2 - 3 qt per acre (2.25 to 3.4 lb ae/acre) Spot treat: use 0.5% to 1.5% v/v solutions. Time: Apply post emergence in late summer to early fall, (August - October) after canes and leaf canopy has reached maturity. Applications should be made  before a killing frost. Comments: Re-treatment may be required to achieve effective control.  Glyphosate is not selective and will harm grasses as well as broadleaf plants.  Use care when working around desirable plants to avoid damage.  Leaves should be sprayed until wet but not dripping to achieve good control.
Product Names: Garlon 4 (triclopyr ester),  Garlon 3A, Element 3A (triclopyr amine) Rate: Broadcast: Triclopyr ester- 1-4 lb ae/acre, Triclopyr amine- 1.5-4.5 lb ae/acre Spot treat: Triclopyr ester use 0.75% to 1% v/v solution, Triclopyr amine use 1% v/v solution Basal Bark: Triclopyr ester- use 20% v/v soultion with basal oil or seed oil. Time: Apply post emergence in late summer to early fall, (August - October) after canes and leaf canopy has reached maturity. Applications should be made before a killing frost. Comments: Re-treatment may be required to achieve effective control.  Triclopyr is selective and will harm desirable broad leaf plants, trees, and shrubs.  Use care when working around desirable plants to avoid damage.  Leaves should be sprayed until wet but not dripping to achieve good control.  Triclopyr ester formulations may volatilize under warm temperatures.
Product Names: Crossbow (Triclopyr + 2, 4D), Capstone (Triclopyr + aminopyralid) Rate: Broadcast: Triclopyr + 2, 4D- 1.5 gallons/acre, Triclopyr + aminopyralid- 6-9 pints/acre. Spot treat:  Triclopyr + 2, 4D- 1.0% to 1.5% v/v solution, Triclopyr + aminopyralid- equivalent to 6-9 pints/acre. Time: Apply post emergence in late summer to early fall, (August - October) after canes and leaf canopy has reached maturity. Applications should be made before a killing frost. Comments: Re-treatment may be required to achieve effective control.  Triclopyr + 2, 4D and Ticlopyr + aminopyralid are selective and will not harm grasses, but may damage desirable broad leaf plants, trees, and shrubs.  Use care when working around desirable plants to avoid damage.  Leaves should be sprayed until wet but not dripping to achieve good control.  Forage and manure derived from areas treated with Ticlopyr + aminopyralid, should not be composted or used around desirable vegetation. Check label for specific warnings and recommendations.
Product Names: Escort Rate:0.5 to 1 oz product/acre (0.3 to 0.6 oz ai/acre) Time: Apply post emergence in late summer when fully leafed out, but before leaf discoloration. Comments: Metsulfuron is primarily active against broad leaf plants and generally will not harm grasses.

Biological:

Blackberry leaf rust fungus (Phragmidium violaceum) is an accidentally introduced European species that can result in defoliation of Himalayan blackberry.  It is not an approved biological control agent.  Infected plants should not be transported due to the potential impact of this species on agriculturally important species.

Disposal:

Small amounts of plant material can be disposed with yard debris, or composted on site.  Avoid composting plants that are seeding.  Seeds may persist in home composting systems and may unwittingly be spread through contaminated compost. For larger patches plants can be chipped and spread on site allowed to decompose.  Alternatively, cut canes can be piled up to dry.  Fresh cuttings need to be kept off of wet ground to prevent resprouting. Once dried the piles can be brunt, be sure to check with your local Fire District or the Oregon Department of Forestry for suitable burn days.

Follow-Up:

Diligence is the most important aspect for controlling Himalayan blackberry.  Blackberry plants will readily resprout following various treatments methods, so repeated follow-up is required.  The seed may persist in the soil for years following treatment, or arrive on site from adjacent and nearby infestations.

Best Management Practices:

Small Infestations:

  • Consider the land use practices on site.  Identify, and site specific considerations that should be taken into account before initiating control.
  • Be sure you can properly identify Himalayan blackberry.  If you are unsure about your weed bring a sample to the Conservation District, and we can help to identify your particular weed.
  • Identify any native or desirable plants nearby, and take precautions to minimize and negative impact to them.
  • Manual removal is very effective at controlling small infestations of Himalayan blackberry.  Plants can be cut with loppers, a saw, or machete at ground level.
  • Use a long board or plywood to mash plants and increase allow access.
  • Dig or pry out the root ball using a Pulaski, shovel, or Shrub Buster.  Remove of as much of the root mass as possible to prevent resprouting.
  • Monitor the site for regrowth, and remove new sprouts as soon as they appear.
  • Small infestations can also be treated using a selective herbicide.  Spot spray techniques work well for small infestations.

Large Infestations:

  • Consider the land use practices on site.  Identify, and site specific considerations that should be taken into account before initiating control.
  • Be sure you can properly identify Himalayan blackberry.  If you are unsure about your weed bring a sample to the Conservation District, and we can help to identify your particular weed.
  • Identify any native or desirable plants nearby, and take precautions to minimize and negative impact to them.
  • Mow down the blackberry using chainsaws, weed eaters, or a brush mower.
  • Allow blackberry plants to regrow and treat with an approved herbicide.
  • Replant large areas to help stabilize soils.  Start with grasses and allow for treatment using a selective herbicide, then slowing incorporate forbs, shrubs, and trees as blackberry populations are brought under control.
  • Continue to monitor the site for regrowth and treat any new infestations.

Fun Facts:

  • The fruits of Himalayan blackberry are edible and makes great pies and jams.
  • September 29th is Poisoned Blackberry Day!  It is the day of the year that people believed blackberries turned bad for the year and were inedible.
  • "Batology" is the botanical study of blackberry brambles.

Additional Information:

References:

  1. Bossard, C. C., J. M. Randall, & M.C. Hoshovsky.  2000.  Invasive Plants of California's Wildlands.  Berkeley, CA: University of California Press.  pp 277-281.
  2. Christy, J. A., A. Kimpo, V. Marttala, P. K. Gaddis, & N. L. Christy.  2009.  Urbanizing Flora of Portland Oregon 1806-2008.  Native Plant Society of Oregon Occasional Paper 3 pg. 218.
  3. DiTomaso, J.M. & E.A. Healy.  2007.  Weeds of California and Other Western State vol 2.  University of California ANR.  pp 1426-1434.
  4. DiTomaso, J.M., G.B. Kyser, S.R. Oneto, R. G. Wilson, S. B. Orloff, L. W. Anderson, S. D. Wright, J.A. Roncoroni, T.L. Miller, T.S. Prather.  2013.  Weed Control in Natural Areas in the Western United States.  Davis, CA: UC Weed Research and Information Center.  pp 341-343.
  5. Holloran, P., A. Mackenzie, S Farrell, D. Johnson.  2004.  The Weed Workers Handbook: A Guide to Techniques for Removing Bay Area Invasive Plants.  Berkeley, CA: California Invasive Plant Council.  pp 60-61
  6. Kaufman, S. R. & W. Kaufman.  2007.  Invasive Plants: Guide to identification and the Impacts and Control of Common North American Species.  Mechanicspurg, PA: Stackpole Books. pp 145-151
  7. King County Noxious Weed Control Program.  2011.  King County Best Management Practices for Controlling Himalayan and Evergreen Blackberry (Rubus aremeniacus and Rubus laciniatus).  http://your.kingcounty.gov/dnrp/library/water-and-land/weeds/BMPs/blackberry-control.pdf  (Retrieved May 23, 2013).
  8. Oregon Flora Project. 2013.  Oregon Plant Atlas: Rubus bifrons.  http://www.oregonflora.org/atlas.php.  (Retrieved May 22, 2013)
  9. Peachy, E., D. Ball, A. Hulting, T. Miller, D. Morishita, P. Hutchinson. eds.  2013.  Pacific Northwest Weed Management Handbook: Control of Problem Weeds.  (Retrieved May 24, 2013).
  10. Soll, J. 2004.  Controlling Himalayan blackberry (Rubus armeniacus, [Rubus discolor, Rubus procerus]) in the Pacific Northwest. The Nature Conservancy.  http://www.invasive.org/gist/moredocs/rubarm01.pdf   (Retrieved May 23, 2013)
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