by Allison Winmill
Technical Manager Forestry & Tree Nurseries
co-authors
Plants, animals, insects, pathogens… Invasive species are a global issue and cause negative impacts to the environment, economy, and/or society.
In North America, there are many invasive species that are present that land managers are challenged with on the landscape. Of those, are two small shrub/tree species which are changing the landscape in both urban and rural settings: common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus).
In many cases, invasive species were introduced or released accidentally to an area outside their natural habitat range. Their addition to an ecosystem is often a disturbance to the natural cycle as these species generally lack natural predators, seriously affecting both flora and fauna, waterways, and often come at a severe economic cost of loss of resources and/or management (Invasive Species Centre 2021).
1 - Invasive buckthorn : what is it?
Common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus) are thought to be introduced as far back as the 1800’s and originally used for things like hedgerows and windbreaks (Anderson 2012).
By the 1900’s it had become widespread, with current distribution ranging across much of North America. In Canada it has been recorded from Nova Scotia to Saskatchewan (Anderson 2012).
Together, both species can occupy a variety of landscapes.
Glossy buckthorn is typically found in wetland areas while common buckthorn generally has a wider range including places like roadsides, riverbanks, mature forests and farm fields (Poole 2014).
Glossy buckthorn can be identified by its generally glossy/shiny leaves which have smooth margins, veins which run parallel to each other from the main vein to the outer leaf edge and are alternate in arrangement.
The leaves of common buckthorn have serrated margins, with veins which curve prominently towards the tip of the leaf and are opposite to sub opposite in arrangement.
Both species have lenticels on the bark, when mature the berries are black in colour, and are both shrub/small tree species (Anderson 2012).
2 - What makes buckthorn such a successful invader?
One of the phenological advantages of buckthorn, which make it such a successful invader, is its ability to be one of the first species to leaf out in the spring which shades out other species in the understory. Additionally, they tend to keep their foliage late in the season.
An early spring leaf out combined with maintaining foliage well into the autumn months gives buckthorn a photosynthetic advantage over other species (Kurtz and Hansen 2018). Further contributing to its photosynthetic capacity is a high nitrogen content in the leaves which allows for quick growth (Whitfeld et all 2013). Therefore, the buckthorn is altering the amount of light reaching the forest floor, altering what can grow on the site.
It also produces high quantity of seed which are readily dispersed mostly by birds, with the added factor of the fruit commonly acting as a laxative, ensuring dispersal which can be quite far from the original population. This combined with seeds generally remaining viable in soil for many years, and a high germination rate, all equate to successful invasion on the landscape (Anderson 2012).
3 - Impact of common and glossy buckthorn?
Impact on woodlands
Both common and glossy buckthorn can form very dense monospecific thickets over large areas which subsequently reduces biodiversity and therefore can alter wildlife habitat 👉.
Over time, it can alter natural woodlot species composition through its ability to outcompete native regeneration and quickly colonize stand openings.
Buckthorn thickets can not only impact natural regeneration but also affect other uses of the forest such as the ability to get equipment on site in a commercial setting, impede recreational activities and wildlife pathways (Whitfeld et all 2013).
It can also significantly affect the soil, for example, the leaves of common buckthorn are highly nutritious and are therefore decomposed quickly once on the forest floor leaving exposed soil as opposed to the more typical leaf litter and organic layer. The exposed soil is suitable for more buckthorn growth, or often other invasive species (Whitfeld et all 2013).
Impact on agriculture
From an agricultural perspective, common buckthorn is also a host for oat crown rust and soybean aphid, both of which can cause a decline in crop yields (Anderson 2012).
Due to its impact on agriculture, common buckthorn is listed as a noxious weed under the Province of Ontario’s Weed Control Act (OMNRF 2021).
4 - Management strategies for invasive buckthorn
Management methods for invasive buckthorn can include a variety of strategies including:
✅ mechanical control (cutting, mowing, girdling)
✅ alone or in combination with chemical products
✅ at a young stage, buckthorn seedlings can also be pulled from the ground (Lindgren 2006)
Once buckthorn is established on a landscape,
it can be incredibly difficult to manage or eradicate.
If considering mechanical treatment alone, it is important to note that it produces prolific stump sprouts post-harvest, potentially requiring several years of repeated cutting.
LALCIDE CHONDRO, a biological herbicide for control of common and glossy buckthorn
From 2016 to 2019, Lallemand Plant Care implemented and completed a series of research trials to explore the use of a biological herbicide, LALCIDE CHONDRO, as an additional tool to aid in invasive buckthorn management.
The work took place in Canada in the provinces of Ontario and Quebec to test LALCIDE CHONDRO against invasive buckthorn in both cut stump and girdling operations. The efficacious results of these research trials led to the existing Canadian label being amended in the fall of 2020 to include use against both common and glossy buckthorn in addition to the already labelled species: alders (red, thin leaf, and Sitka), trembling aspen, red oak, ironwood, white birch, sugar maple, and choke cherry.
What is LALCIDE CHONDRO?
The product has the active ingredient of Chondrostereum purpureum, a globally naturally occurring wood decay fungi which can readily be found in Canadian forest ecosystems.
The formulation is a paste and is registered to prevent resprouting and regrowth from cut or girdled stems.
It works via two modes of action:
✅ First by colonizing the stump itself and
✅ Secondly by releasing an enzyme which causes silver leaf disease in post-harvest sprouts which contributes to overall stem mortality.
Application of LALCIDE CHONDRO
LALCIDE CHONDRO requires a one-time application per stem and is applied directly to a freshly cut stump top or to a girdling wound.
Timing is an important factor when it comes to product application, in order to target the buckthorn when it is fully leafed out and reserves in the roots are exhausted.
This window is late spring to early summer, typically mid-June to early July depending on climatic conditions.
Risk to non-target species
Chondrostereum purpureum is a naturally occurring fungus that is readily found in forest ecosystems. The risk to non target tree species is very minimal since LALCIDE CHONDRO requires a concentrated and targeted application to a fresh wound.
It is also a paste, therefore not airborne in the application, and is applied directly to the target stem requiring control.
Benefits of using LALCIDE CHONDRO
LALCIDE CHONDRO is a biological solution which can be another tool in the toolbox for invasive buckthorn control for managers who may be limited with chemical herbicide use both from a public and/or regulatory perspective. It also provides a more environmentally sensitive option as it is a naturally occurring microorganism.
Research trials
Research trials conducted by Lallemand Plant Care compared plots where the microbial biofungicide was applied on cut stump and girdle stem to control plots (buckthorn cut/girdled, but no product applied).
The results were incredibly visual as seen in the pictures below of one trial location showing results 24 months post-harvest and application. Due to the biological nature of the product, it takes time for efficacy to be fully expressed, as the fungus needs time to colonize the stump.
To learn more about these research trials and associated results, as well as how LALCIDE CHONDRO could play a role in your buckthorn management strategy please feel free to visit our website at bioforest.ca or contact one of the technical specialists for more information through support@bioforest.ca.
5 - References
- Anderson, Hayley. 2012. Invasive Common (European) Buckthorn (Rhamnus cathartica): Best Management Practices in Ontario. Ontario Invasive Plant Council, Peterborough, ON.
- Invasive Species Center. 2021. Learn about invasive species. https://invasivespeciescentre.ca/learn/
- Kurtz, Cassandra M.; Hansen, Mark H. 2018. An assessment of common buckthorn in northern U.S. forests. Res. Note NRS-250. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern
- Rese Lindgren, C. 2006. Common buckthorn and glossy buckthorn. Invasive plants found in Manitoba Rhamnus cathartica L. and R. frangula L. (syn. Frangula alnus Mill.). Alien Invasive Aquatic and Wetland Plants Fact Sheet Series. 6pp.
- Ontario Ministry of Natural Resources and Forestry (OMNRF). 2021. Common buckthorn. https://www.ontario.ca/page/common-buckthorn.
Poole, J. 2014. Common & Glossy Buckthorn Factsheet. Nottawasaga Valley Conservation Authority. 2pp. - Whitfeld, T., Reich, P., Lodge, S., Roth, A., Buschena, C. 2013. Preventing and managing common buckthorn invasion: recent research and recommendations. Department of Forest Resources, University of Minnesota. 6pp.
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