August 15, 2023

Kaidi Tingas

We test new techniques for alien species control in 44 areas

This summer, tests to control four large-growing alien species — knotweeds, false spiraea, goldenrods and snowberry — started by using innovative methods, including geotextile coating and hot steam treatment! Two of these species, goldenrods and knotweeds, are invasive alien species, the cultivation and distribution of which is prohibited in Estonia! But the two others, the false spiraea and the snowberry, form life-threatening thickets when they spread from gardens into the wild, and then it is almost impossible for other plants to in survive in the areas which have been overtaken.

We carry out control tests across Estonia in 44 areas, both on private and state land; all the owners of these areas have agreed to the works over the next five years! The test areas also receive the corresponding markings, and experience so far has shown that passers-by have a high interest in these activities and their knowledge of alien species is also quite good. In addition, 16 control areas have been selected.

All those alien species are treated with hot steam, combined with mowing, crushing and trimming. Since the knotweed was already four metres tall by the beginning of June, when the works started, it had to be cut first before the steam machine could even be used at all! Last week, the plants were steamed for the third time, and as can be seen in the photos, the result is impressive! However, it is not possible to get rid of knotweed or other alien species in one summer, so the works will continue in the following years. During this time we also collaborate with soil scientists from the University of Tartu.

Steam from hot water is one hundred per cent natural, the plant withers almost immediately after it is steamed. The tank holds 500 l of water which allows for an hour and a half of work. ‘The same effect can be achieved by throwing boiling potato water where needed, but it takes considerably more time,’ said Merike Linnamägi, adviser to the Department of Nature Conservation of the Ministry of Climate, while keeping busy with a steam hose. Testing the steam machine is Merike's idea, and getting it to Estonia is her long-standing dream.

There are probably no other similar steaming machines in Estonia at the moment, and the Environmental Board acquired with the help of the environmental support of the European Economic Area. In Western Europe, a similar machine is also used for cleaning park benches, sculptures and among other purposes.

In the continuation of successful control tests, we want to introduce different control methods to municipalities as well as to enthusiastic individuals and gardeners! Species-specific educational films will also be ready for autumn, and the TV programme ‘Ozone’ will also feature a story about the control tests on alien species.