Invasive plants – what are they and how are they dangerous to humans and the environment?

"An alien invasive species is an alien species whose introduction and spread threaten ecosystems or species and cause economic or environmental damage." In other words, these are alien organisms, plant species, whose spread and numbers pose a threat to the life or health of citizens. Invasive alien species are considered one of the main threats not only to biodiversity; their expansion leads to serious ecological, social, and economic consequences. One of the striking examples of invasive alien species in Europe is giant hogweeds, among which Sosnowsky's hogweed is the most dangerous invasive plant species in Belarus.

According to the V.F. Kuprevich Institute of Experimental Botany of the National Academy of Sciences of Belarus, there are over 300 species of invasive (alien) plants growing in Belarus. In 2011, the list of the most dangerous among them was updated. Among these plant species that have become widespread in our republic, a group of particularly aggressive ones can be identified. This group of species is small, but the negative impact of their spread is significant. The most prominent representatives include: Heracleum sosnowskyi Manden. – Sosnowsky's Hogweed, Solidago canadensis L. – Canada Goldenrod, Echinocystis lobata (Michx.) Torr. et Gray. – Wild Cucumber, Acer negundo L. – Box Elder, Robinia pseudoacacia L. – Black Locust.

SOSNOWSKY'S HOGWEED – a very large (up to 3 meters) biennial or perennial plant of the Apiaceae family. The plant releases a transparent phototoxic sap, which causes burns when it comes into contact with human skin and is exposed to ultraviolet radiation. Sosnowsky's Hogweed poses a threat to human health and causes environmental problems, as due to its rapid population growth, it displaces other plants and maintains a dominant position in the areas it occupies.

In Belarus, it grows along deposits, field edges, and roadsides as a wild or introduced plant, forming large thickets in places. In its habitats, it almost completely displaces native vegetation, forming plant communities uncharacteristic of our territory in composition and appearance. Sosnowsky's hogweed can grow everywhere, in all soil and climatic zones of the republic. It is most often found along roads (from major highways to small forest paths), as well as adjacent areas (ditches, slopes, etc.)

Various methods can be used to combat Sosnowsky's hogweed, the main ones being manual and mechanical, which include digging up and destroying the root stalks, cutting or mowing the plants, and removing inflorescences.

Recommended timing for the destruction of Sosnowsky's hogweed: manual method (before flowering, early spring and mid-summer) and mechanical destruction (at least 2-3 times per season, preventing flowering and seed formation), mowing (at least 3 times per season, from spring until the plant begins to flower), plowing (before flowering followed by disking, at least 4 times per season), sowing with grass mixtures or forest crops.

Improving the phytosanitary situation by manual and mechanical methods alone is labor-intensive and requires significant costs, so the use of herbicides is of great practical importance. Treatment with pesticides "Tersan", "Grader", "Buran", "Super" is effective in early spring if the plant height does not exceed 30 centimeters and in summer after mowing.

CANADA GOLDENROD (hereinafter referred to as goldenrod) is an alien invasive plant species for the Republic of Belarus. It is included in the list of particularly dangerous invasive plant species. Some people grow it on their household plots and around their homes. However, its use in landscaping is prohibited. The uncontrolled spread of this species leads to the suppression and even complete displacement of other plants from natural ecosystems. In meadow and floodplain ecosystems where goldenrod settles, the composition and structure of hayfields change, the quality of harvested hay significantly deteriorates (cattle do not eat it), large, stiff sods are formed, the development of which hinders the growth of many economically useful plants, and the structure and aeration of soils change. In floodplain meadow communities, goldenrod poses a threat to populations of many rare and endangered plant species, disrupts sowing structure, and reduces crop yields.

However, it should be noted that, first and foremost, Canada goldenrod is an allergenic aggressive plant; each individual produces over 20,000 seeds (with a germination rate of 50-90%), which pose a threat to human health by increasing the incidence of diseases, as goldenrod pollen provokes allergic reactions in people. (Blooms in July-September, achenes ripen in August-October).

In recent years, the danger from this plant has increased; the species has significantly increased its numbers (by an average of 15-20%) and its distribution range, leading to transformations of natural complexes. Canada goldenrod is a quarantine plant, prohibited from being moved across borders and imported into many countries.

Control measures for goldenrod include mowing twice a year (in May and August) and, most importantly, timely removal and disposal of mowed plants, as seeds can ripen on the ground and germinate the following year. Good results are achieved by digging the soil in the summer during dry weather, and the use of herbicides is also effective when plants are no more than 10-15 cm tall, as goldenrod's sensitivity to them significantly decreases later.

CUCURBITA LOPASTNAYA (hereinafter - echinocystis) - one of the most aggressive and actively spreading invasive species, increasing its distribution area by 40-50% almost annually. Echinocystis is an annual monoecious herbaceous plant. It blooms in July-September, fruits from August, and only male specimens bloom beautifully. Females have more modest inflorescences and immediately develop spines. It is cultivated as an ornamental plant. It is found in populated areas, among shrubs, along the banks of reservoirs. It grows in wastelands and shrubs near residential areas, in gardens, summer cottages, and along coastal shrubs along rivers. Since the cessation of cultivation for ornamental purposes will lead to a significant reduction in invasive populations, the strategy for combating this species should focus on public awareness and the prohibition of its cultivation and use in landscaping. Echinocystis can be weeded out and, in limited areas, can be quickly eradicated.

ACER NEGUNDO - is very active and mobile, has a high growth rate and is resistant to air pollution. It turned out that its fallen leaves are so caustic that they displace oak groves. It colonizes the vicinity of cities and towns, initially in disturbed areas, but soon penetrates natural communities. The dispersal process is relatively fast, as it enters the fruiting stage at the age of 6-7 years, and its generational turnover is faster than that of other tree species.

In urban conditions, it is a malicious woody weed. The pollen of male specimens of Acer negundo is a strong allergen; during the spring flowering period, the wind carries it over long distances, and its presence in the air causes pollinosis in humans (a disease called "hay fever"). Scientists know that with good wind, maple seeds, resembling small helicopters in flight, can fly more than a kilometer away from their parent tree. According to research, it is a carcinogen. The leaves emit an unpleasant odor when rubbed.

Due to the fact that box elder (Acer negundo) is a woody plant, the strategy for controlling it has its peculiarities. Since 2016, simplified procedures for the removal of this invasive woody plant have been established by law. Removal is carried out based on an act confirming the presence of the plant's growing site. A copy of the act confirming the presence of the growing site of plants belonging to species whose distribution and numbers are subject to regulation is sent by the land user to the local executive and administrative body on the day of its issuance.

ROBINIA PSEUDOACACIA (hereinafter referred to as robinia) is also an alien invasive plant species for the Republic of Belarus. The bark and fruits contain toxalbumin (a toxic protein) – robin. Glycosides (robinin, acacia, apigenin, etc.) and essential oil are found in the flowers. The bark and wood contain tannins (2 to 4%), phytosterin, and an essential oil with the pleasant strong scent of acacia flowers, containing methyl anthranilate, indole, heliotropin, benzyl alcohol, linalool, and α-terpineol. The toxalbumin robin has a neurotoxic effect. Poisoning causes nausea, vomiting, and abdominal pain. In severe cases, hematuria, acute cardiovascular failure, severe psychomotor agitation, convulsions, and loss of consciousness develop.

Control measures are similar to those used for box elder:

- prohibition of the use of this plant in landscaping;

- removal of trees.

In conclusion, it should be noted: do not use these plant species (Heracleum sosnowskyi, Solidago canadensis, Echinocystis lobata, Acer negundo, Robinia pseudoacacia) for landscaping and beautification on personal plots and territories adjacent to residential buildings and organizations. It is not too late to control the spread of alien plant species.

We kindly ask land users to prevent the spread of harmful alien plants by any of the above-mentioned means; taking appropriate measures for their eradication is the key to success.

The removal of the invasive tree species box elder (despite its widespread distribution and "familiarity" in the urban landscape) is fully permissible under current legislation and is fully justified.

Please note that landowners on whose land wild plants are growing are liable in accordance with the legislation of the Republic of Belarus for failure to take timely measures to eradicate invasive plants.