The situation of Heracleum mantegazzianum and H. sosnowskyi in Estonia
In Estonia, Heracleum sosnowskyi and H. mantegazzianum are registered on the list of non-native species of the Estonian Nature Conservation Act that are likely to disrupt the natural balance. These two Heracleum species threaten native communities and species distribution, and represent a threat to human health. The first report of H. mantegazzianum in Estonia dates from 1900, and H. sosnowskyi was first recorded in this country in 1957. Invasions started in the 1950s, when these Heracleum species were used for silage and as honey plants. Although their impact on human health was quickly discovered, the use of these two plants was promoted until the 1980s.
In Estonia, the Ministry of environment has been involved in the mapping of Heracleum spp. populations since 2003, and in eradication actions since 2005. At present, more than 1 000 known Heracleum spp. populations cover 1 300 hectares in Estonia. Approximately 75% of the known populations are situated on private lands, and about 25% of all populations are small (<50 m2) and easily manageable. Two hundred and thirty five hectares (235 ha) were under eradication in 2005, this area progressively increased to 605 ha in 2006, 609 ha in 2007, 886 ha in 2008, and 861 ha in 2009. In 2010, the estimated area under eradication was 1 210 ha, and the annual budget dedicated to this effort was 6.8 million EEK (~435 000 EUR). The map of the 2010 eradication campaign for these two Heracleum species is available at the following address: http://xgis.maaamet.ee/xGIS/XGis?app_id=MA13&user_id=at (plant populations can be observed by zooming).
Management practices included glysphosate treatments and manual removal of the plant. All plant populations are managed, except when:
- they are situated in rocky riversides (as it is impossible to dig up the plant and prohibited to use glyphosate on this type of land),
- they occur near the Russian border, as nothing is done on the Russian side,
- when large populations are present on organic farms (as it is impossible to apply glyphosate, and large stands cannot be manually removed).
As a result of this eradication campaign, in 2010, about 160 populations (55 ha) have been eradicated but are still under observation. Estonia aims to eradicate Heracleum spp. and it is estimated that eradication could require at least 10 more years of management efforts. A new management plan will be implemented after 2010 to trying to find solutions for the currently untreated sites (river banks, Russian border, or organic farms), as well as to increase the motivation of the private landowners and contractors to manage the species
on their properties. The responsibility of these eradication plans would in the future be transferred to the landowners.
Personal communication with Merike Linnamagi, Estonian Ministry of the Environment, Merike.Linnamagi@envir.ee