A record amount of alien waste was accumulated

The City of Riihimäki thanks its residents for their hard work in combating the Spanish snail. The rainy and cool early summer was exceptionally favorable for the reproduction of Spanish snails. There were many sightings of snails from different parts of the city. Residents collected more Spanish snails than ever during the summer. Between April 29 and October 15, 2025, approximately 13,700 kilograms of snail waste were collected.

"Residents managed to collect a huge number of Spanish hornets this year compared to the previous peak year of 2020. Warm thanks to all residents who participated in the control of harmful alien species both on their own properties and in the city's parks and green areas," says Anne Kulhoranta, Invasive Species Coordinator.

The Spanish snail is a harmful alien species that easily displaces native snail species. It reproduces quickly and eats a lot. The omnivorous Spanish snail is suitable for both ornamental and useful plants, and it can cause great damage in the garden.

The city intensified prevention measures

During the summer season of 2025, a total of 31 snail bins were in use in the Riihimäki area. Three new snail bins were added during the summer: in Uhkola, Tienhaara and in front of the hospital. During the season, the snail bins were emptied at most twice a week, a total of 22 times.

Enhanced mowing continued as in previous years and the mowing areas were expanded. In practice, mowing was carried out almost daily at some snail site, either with line cutters or a tractor mower.

A total of approximately 1500 kilograms of Spanish snail pesticide was applied during the season, to approximately 340 different targets. The pesticide application was repeated 2–4 times on most targets.

In addition to mowing and pesticide application, the city organized 6 snail walks, where Spanish snails were collected together with residents.

A single Spanish hornet can lay several hundred eggs per year. The species has no natural enemies in Finland, so populations can grow uncontrollably. Prevention of spread and rapid response are the most important things in control.

Alien plant waste was also disposed of

Over 13,000 kilograms of alien plant waste were also delivered for disposal during the season. The amount of alien plant waste consisted mainly of the harmful species rowan and rosehip. The amount of plant waste was increased by the start of the control of rowan.

For more information about the city's invasive species control, visit the Invasive Species page.

Locations of snail dumps (kartta.riihimaki.fi)