Little research has focused on slugs, although five to ten of about thirty species in Hungary are potential or actual pests. Since 2018, the systematic exploration of the Hungarian fauna has been going on at the Plant Protection Institute of the Agricultural Research Center, and during this time seven species with new or uncertain data have been discovered in the Hungarian fauna.
Some are considered invasive species based on international literature, and many are documented pests. In Hungary, the Spanish slug caused the most serious damage. In our article we present the main trends and findings of domestic slug research, as well as the most common pest control methods.
Hungarian slugs recorded 26 species prior to 2018 based on literature data. Then, as part of the PhD research, extensive exploration of the range began, with the help of national surveys, ‘citizen science’ methods (Facebook calls, internet surveys, etc.) With Páll-Gergely Barna. that’s it: Ambigolimax parvipenisAnd Ambigolimax ValentianosAnd Deroceras invadesAnd Krynickillus melanocephalusAnd Limacus maculatusAnd Milax nigricans And Tandonia Koseri. Interestingly, the researchers described the first listed nudibranch as a species new to science in 2022, after discovering in their synthesis work an error resulting from the incorrect identification of several genera and species of nudibranch, which had accumulated in the literature for decades.
Based on their results, the nudibranch, previously classified as a different species, was described as a new species due to its reproductive differences, and the species name was given Ambigolimax parvipenis.
Their results were also confirmed by molecular data.
We currently have no data on the damage caused by the listed mollusks in Hungary, which could be explained by their recent discovery. However, there are several species for which international literature indicates damage (eg a. Valentianus In England it causes great damage and breeds in great numbers), and we also know of one of its well-documented pest relatives. slug in Budapest (Tandonia budapestensis) is, for example, a species native to soil-destroying native animals.
The introduction of alien species can be mainly facilitated by two factors: climate change and the promotion of international trade.
While it is difficult to prove the consequences of climate change due to the combined influence of many factors, there are indications of the role of international trade that can be easily observed.
The fact that four out of seven non-native slug species identified over the past five years were only discovered in Budapest gardens and in the Füvészkert could be evidence that networks of stores and greenhouses dealing with imported plants are hotspots for the transfer of non-native species across national borders.
Above ground and below ground
According to our current knowledge, the slugs that cause the most damage in Hungary are the Spanish slugs (Arion vulgaris), retinal slug (Deroceras reticulatum), yellow-scale alloy (Arion Vasiatos), and Budapest slugs (T. budapestensis) and the cellar slug (Limacus flavus).
The most common damage can be above ground: slugs can chew on fresh leafy greens or pumpkin fruits, strawberries, and ornamental plants (eg Spanish slug, reticulated slug).
In addition, underground damage may occur, when the animal burrows itself into the soil and destroys the tubers of root vegetables or potatoes while moving there (such as the Budapest slug). The so-called storage pests (such as the slug that lives in the cellar) chew products (apples, carrots, potatoes) stored in cool and damp storage rooms.
It is difficult to estimate the extent of the damage for several reasons. Most mollusks lead a hidden, nocturnal lifestyle, so it is difficult to accurately determine the “culprit” of the damage. In order to find out which species have caused damage to the plants of our kitchen gardens in the morning, after sunset, we must look for the culprit with a headlight, but this only happens in rare cases. So, there is a lot of unverifiable anecdotal data out there, the best example being a large slug often found in water wells and other cool places (Limax maximus), which are often blamed, although in most cases these species are not responsible for the damage.
not choose
One of our best documented pests is the Spanish slug (A. vulgaris). During an online survey (in 2018), we were interested in researching whether those who filled out the questionnaire knew about the Spanish slug, and if so, where they encountered it, whether it causes them harm (if so, what kind of harm), as well as the methods they use to protect themselves against it and how effective it is.
A total of 853 questionnaires were received, from which it was found that this species is widespread throughout the country, except in the dry areas of the Great Plain, but is found in greater numbers in the cooler and wetter regions of Transdanubia.
86% of the respondents indicated that the Spanish slug causes some amount of damage to the vegetables of their gardens. This type of dangerous pest, breeding in large numbers during periods of rain, adapts well to human disturbances, and is not picky about its food. Most people mentioned lettuce, legumes (peas and beans), strawberries and various ornamental plants (daylily, velvet flower, petunia, etc.) as the crops most affected by the destruction. The estimated national damage could reach 1 billion forints annually. The survey revealed that the majority of respondents are trying to use some method to protect themselves from Spanish slug destruction. Most people simply pick them up and destroy them physically (using some sort of tool, eg a shovel), but it’s also common to use metal-containing snail killer granules (nowadays a plant protection qualification is required to purchase this). Many people sprinkle the area they want to protect with a hygroscopic substance (salt, lime, ash, etc.), and the beer trap is also widespread: by pouring beer into a container and digging it up, volatile substances attract slugs, which fall into 5% alcohol and die.
The best example of a biological control method is the keeping of Indian nudibranchs, which can be used to prevent long-term damage to Spanish nudibranchs.
In general it can be concluded that there are kitchen garden pests among the slugs, and we can meet more and more cases of non-native and sometimes invasive species. Among them, there are suspected and well-documented species that cause serious damage, which is why it is necessary to monitor international trends and local populations in the future.
Agnes Torosi
Research Assistant
ELKH ATK Institute for Plant Protection
