The oak processionary moth is actually a fairly inconspicuous butterfly. However, its caterpillars, which appear in large numbers in some years, can become a serious problem: the animals are highly toxic to humans and animals. In this article you will find out whether there is an obligation to report and what you can do against the pest.
Is there an obligation to report oak processionary moths?
There is no legal reporting requirement for the oak processionary moth in Germany (as of September 2019). However, if you see poisonous caterpillars, it makes sense to inform the responsible authorities (green spaces department, he alth department or public order office) in order to minimize risks to people and the environment.
What is the oak processionary moth?
The oak processionary moth is a nocturnal butterfly that flies between late July and early September in warm and dry years. The inconspicuous gray-brown colored butterfly has a wingspan of between 25 and 35 centimeters, with the females being slightly larger than the males. A single female lays up to 150 white eggs, approximately one millimeter in size, from which the poisonous caterpillars hatch in early May. These go through about five to six stages of development until they pupate in late June to early July. The caterpillars are often found in large numbers on tree trunks and branches, where they stay in webs during the day. At dusk, the animals wander into the treetops to feast on leaves and tender shoots.
Occurrence and distribution
The oak processionary moth originally comes from southern Europe, where it causes great damage, especially on the Iberian Peninsula. In recent years, however, the butterfly has also spread to other European countries as far north as Finland and southern Sweden. In Germany, all federal states are now affected, but especially Berlin and Brandenburg, Saxony-Anh alt as well as North Rhine-Westphalia, Baden-Württemberg and Bavaria - i.e. everywhere where there are oak-rich forests and oak-lined street avenues in rather flat regions.
Why is the oak processionary moth so dangerous?
The following video shows very impressively why you should not take an oak processionary moth infestation lightly and also how difficult it actually is to sustainably combat the poisonous caterpillars:
Gefährliche Eichenprozessionsspinner (SPIEGEL TV)
Danger to humans
Each individual oak processionary moth caterpillar has up to half a million poisonous stinging hairs that break very easily and are often spread over long distances by the wind. For this reason, the animals are dangerous not only when in direct contact, but also when you go near them. The hairs contain the toxin thaumetopein, which is a nettle poison.
Who is particularly at risk?
The following list clearly shows which people and which areas of public life are particularly affected by the oak processionary moth.
| People at particular risk | Particularly vulnerable places |
|---|---|
| Athletes, walkers and hikers in the forest | Towns in and around oak forests |
| Residents near the forest | Playgrounds, kindergartens, schools, public buildings near forests or parks |
| Forest workers and other outdoor workers (e.g. road workers, construction workers, etc.) | Street avenues, rest stops, parking lots with trees |
| Kindergarten children, students, public sector employees | Campsites and sports facilities |
Possible symptoms after contact with caterpillars
The poisonous caterpillar hairs cause typical allergic reactions like these:
- severely itchy skin rashes
- painful inflammation of the skin
- Redness
- Hives, blisters and swelling
These symptoms are also collectively known as caterpillar dermatitis and are very unpleasant. In severe cases, a so-called allergic shock can occur, which is an acute risk to life and the emergency services must be called immediately. Inhaling the hairs can also cause irritation to the mucous membranes in the mouth and nose, which can ultimately even cause bronchitis or trigger asthma. Furthermore, affected people often feel tired and complain of circulatory problems. Sometimes fever occurs.
Excursus
What can you do against caterpillar dermatitis?
In the event of caterpillar dermatitis, please consult your family doctor or an allergist immediately or the emergency service outside of normal local office hours. They will prescribe appropriate cortisol supplements and antihistamines to relieve symptoms. These are usually tablets that have to be taken several days in a row. However, if the symptoms are severe, the doctor can also inject the active ingredients directly and thus achieve a faster effect.
How to protect yourself
However, there are things you can do to avoid suffering from the symptoms mentioned above in the first place. The following measures will help prevent the worst after contact with the oak processionary moth:
- Take a shower and wash your hair immediately.
- Rinse your eyes with clean water.
- However, do not rub your eyes with your fingers.
- Wash your worn clothing thoroughly in the washing machine at 60 °C.
- Do not take off your clothes and shoes in the living area, but outside.
If you are already suffering from itching, this can be relieved by rinsing the affected areas with clear, cold water.
Danger to the forest
Oak processionary moths also cause considerable damage to the forest
The hairy caterpillars of the oak processionary moth are not only dangerous for humans and animals, but also for the forest. If the animals appear in large numbers and on larger areas, as has happened more and more frequently since the 1990s, they eat the affected trees almost bare. These need a lot of strength for the subsequent regeneration, whereby if the trees are deforested over several years, the vitality of the trees decreases significantly and they become more susceptible to further pest infestation and diseases. As a result, the affected trees stop growing, no longer produce acorns and ultimately die.
When is the oak processionary moth particularly common?
The oak processionary moth caterpillars hatch from the beginning of May, although they are not yet poisonous at this point. The fine, poisonous stinging hairs only develop in the third larval instar. However, they remain dangerous for a particularly long time, because the larval skins and hair remain in the nests after each molt and after pupation - and can continue to cause problems for up to a year. For this reason, not only the caterpillars themselves, but also abandoned web nests are a source of danger.
You found a caterpillar nest? This is what you have to do now
Never touch a caterpillar nest or the caterpillars and keep your distance as much as possible! The fight should only be carried out by appropriately equipped specialists.
The oak processionary moth is particularly prevalent in some regions of Germany, so the authorities there are taking drastic measures to contain it. This includes, among other things, the large-scale application of insecticides to stop the spread of the butterfly in the forests. In the following sections we will explain what you can do after finding a web nest or caterpillars.
Is there a legal obligation to report?
First of all: If you have found oak processionary moth caterpillars, you do not necessarily have to report them to the authorities. There is currently no legal reporting requirement for this in Germany (as of September 2019). However, it still makes sense to report it to the responsible authorities in order to secure infested locations and counteract a massive infestation. This applies especially to public places and spaces such as city forests, parks, kindergartens and schools, playgrounds, etc. By reporting the nests, you ensure that authorities can take action and no one gets hurt.
Even if there is no obligation to report, it makes sense to report oak processionary moths
Where can you report found caterpillar nests?
If you have discovered oak processionary moth caterpillars, you can report them informally - for example by calling or sending an email - to one of the following offices responsible for you:
- Green Space Office, Office for Urban Greenery
- He alth Department
- Public Order Office, Town Hall
If in doubt, you can find out from the authorities mentioned who you should actually submit your report to. Describe exactly when and where you found the caterpillars. You might also send a photo as an email attachment to show the location and the level of infestation. The authorities in some cities and districts have also published the names and telephone numbers of the responsible employees on their websites.
What do you have to do if the caterpillar nest is on your own property?
If such a web nest is on your own property, do not touch it under any circumstances. Do not try to destroy it yourself, for example by setting it on fire - this will only stir up the fine stinging hairs. Instead, contact specialized pest controllers who will then arrive with protective suits and suitable equipment and eliminate the infestation. The caterpillars and their nests must then be disposed of separately, which is usually done by burning them in a hazardous waste landfill. Under no circumstances should the webs end up in the household waste or even on the compost!
Who pays for the removal of the caterpillar nest?
If the caterpillar nest is on your own property, you must cover the costs of removing it yourself. In some federal states - for example Berlin - the authorities can order and have such a removal carried out over your head. However, if the nest is on public property, you can report it, but you don't have to pay anything afterwards.
Oak processionary moths in public spaces should also be reported
Frequently asked questions
Is the oak processionary moth also dangerous for dogs?
Of course, not only people, but also dogs, cats, horses and other domestic and farm animals are at risk from the oak processionary moth. Make sure that your animals do not come into contact with the poisonous caterpillars under any circumstances.
Do oak processionary moths also attack other tree species?
As the name suggests, the oak processionary moth primarily attacks oak trees. All types of oak are affected. However, especially in years of severe infestation, the caterpillars can also be found on other tree species, with hornbeams being particularly affected. The animals are mainly found on isolated trees and on the edges of forests.
Are web moths and oak processionary moths the same thing?
The web moths are also butterflies whose offspring eat entire trees bare. In contrast to the caterpillars of the oak processionary moth, these are not poisonous, especially since they are different species.
Tip
In early summer, look out for signs that say “Caution, Caterpillars” or others. These mark areas contaminated with oak processionary moth caterpillars that should, if possible, not be entered.
