Actually, the caterpillars of the oak processionary moth seem quite harmless. But the impression is misleading: Not only can the poisonous stinging hairs of the animals cause a severe allergic reaction in humans and animals, but the caterpillars have been threatening oaks and other trees due to their mass occurrence in recent years.

The stinging hairs of the oak processionary moth are very poisonous

Table of Contents

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  1. the essentials in brief
  2. Health hazard from caterpillars
  3. prevention and defence
  4. combat
  5. features
  6. distribution
  7. biology and way of life
  8. Oak dieback by caterpillars
  9. frequently asked Questions
  10. Can the oak processionary moth also be dangerous to pets?
  11. There is a warning sign in our city park. Why should one avoid entering an area infested with caterpillars?

    12. the essentials in brief

    • Oak processionary moths can cause aggressive rashes, including conjunctivitis and respiratory diseases
    • An oak processionary moth infestation should be reported to the health or regulatory office
    • Oak processionary moths are collected or vacuumed off by professionals and/or combated biologically or chemically

    Why is the oak processionary moth so dangerous to humans?

    Oak processionary moths can cause severe rashes in humans. It is not only villagers whose houses are near forests that are particularly affected. Other groups of people and people who frequently stay in certain places are also at risk:

    Affected locations and areas Affected groups of people
    kindergartens, schools and playgrounds Children and adults in appropriate facilities
    Sports fields and other outdoor sports facilities, outdoor swimming pools, campsites Those seeking relaxation, visitors to sports and other leisure facilities
    Parks and other public green spaces, wooded cemeteries Those seeking relaxation, walkers, hikers, residents
    wooded recreational areas Employees and workers in gardening and landscaping, from green space and cemetery offices, road maintenance, forestry workers, construction workers, etc.
    Roads, highways and service areas, parking lots (through street trees and avenues) Drivers, cyclists and pedestrians

    The following video explains and shows very well what the stinging hairs of the oak processionary moth can do to humans:

    youtube

    Symptoms are similar to an allergy

    The symptoms, which are very similar to an allergic reaction, appear after contact with the caterpillar's poisonous stinging hairs. You don't even have to have touched the animal directly, because the easily breaking hairs also float in the air - especially on windy days. The hairs contain a contact poison, which can lead to the following symptoms in humans and animals:

    • severe itching
    • flushed skin
    • Formation of wheals, nodules and pus blisters
    • Conjunctivitis when the hairs come into contact with the eyes
    • Inflammation of the respiratory tract if the hairs have been inhaled

    In severe cases, acute shortness of breath can also occur, in which case you absolutely have to call the emergency doctor! If you come into contact with the oak processionary moth not just once, but more often, a real allergy can also develop.

    Typically, the symptoms only appear a few hours after contact with the poisonous hairs, so that many people initially make no connection between their discomfort, the rash and yesterday's walk in the woods.

    When do you have to go to the doctor?

    In any case, you should consult your family doctor or a dermatologist and have them prescribe antihistamines and anti-inflammatory creams to counteract the often very severe itching. In the case of conjunctivitis and shortness of breath, other medications are also needed as soon as possible to prevent worse consequences and inflammation.

    caterpillar touched? You must do this now

    If you were traveling in a contaminated area or even touched a caterpillar or a web, you can mitigate the bad consequences by taking the following measures:

    • remove worn clothing and wash at 60 degrees Celsius
    • take a shower immediately, lather and rinse your skin and hair several times
    • rinse out eyes, nose and mouth in particular with clear water
    • Get advice from the pharmacy and get an antihistamine ointment as a precaution

    Then you have to wait and see, because the first symptoms only appear after a few hours or even the next morning. Incidentally, if the reaction is severe, it can also be accompanied by fever, dizziness and fatigue.

    prevention and defence

    Anyone who discovers an infestation of oak processionary moths should keep their distance as far as possible

    Of course, it is best if there is no close contact with the oak processionary moth and thus health impairments. How to prevent:
    • Never touch caterpillars or webs
    • instead, keep your distance and don't sit on the ground when you're nearby
    • if infested areas are known: do not enter them
    • the fine hairs also fly about in the air
    • protect uncovered parts of the body (arms and legs, neck) with suitable clothing when walking in the forest
    • only enter infested areas if absolutely necessary and with full protective clothing (e.g. for professional reasons)

    Oak processionary moth in the garden

    If you have found the caterpillars and their web nest in your garden, do not under any circumstances remove it yourself! Instead, hire a pest controller or an experienced arborist. Do not spray the caterpillar nests with a jet of water or flame them: This will stir up the fine poisonous hairs and spread them around.

    Combat oak processionary moths

    Under no circumstances should you take on the fight against the oak processionary moth yourself, but leave it to the trained professionals. As a rule, these advance very quickly in populated areas, but in the forest control measures are only necessary in the event of a severe infestation.

    Caterpillars found? This is where you should report your find

    Due to the high degree of health risk for humans, animals and nature, there is an obligation to report if you have discovered oak processionary moths or a spider's nest. Municipalities try to kill the pest before the third stage of caterpillars has formed, using methods such as suction, burning, or the application of insecticides. In the event of a discovery, you can contact the responsible health or public order office.

    Natural enemies

    Luckily, the oak processionary moth has many natural predators that are immune to its venom and prefer the caterpillars to eat instead. Species of birds such as the cuckoo and the strikingly colored oriole are included, as are these parasites and predatory beetles:

    • bugs
    • caterpillar flies
    • parasitic wasps
    • Big and small doll robber

    However, the natural predators cannot fight the population alone in the event of a mass occurrence, especially since only a few bird species dare to attack the poisonous caterpillars. However, a settlement of these animals in the garden helps to prevent or keep a possible infestation in check.

    control methods

    When it comes to combating the oak processionary moth, professionals use a variety of methods, some of which are controversial, especially among environmental groups.

    Mechanically and thermally

    There are three different mechanical or thermal methods for combating the caterpillar, all of which are used from around the end of May:

    proceedings execution Per cons
    suction Extraction of caterpillars, webs and their contents using special devices residue-free, gentle on the surrounding nature cumbersome, not very suitable for mass infestations
    burn down Burning of the caterpillars and the web nests by gas burners complete destruction of the organic material Stirring up the poisonous hair, damage to the tree, risk of fire
    collect Glue the web nests together with the caterpillars using suitable preparations and then remove them residue-free, gentle on the surrounding nature cumbersome, not very suitable for mass infestations, danger for those carrying out the work

    The resulting biological waste is classified as corrosive industrial waste and is completely disposed of in a special incineration plant.

    Chemical and biological

    Many municipalities fight a mass occurrence of the oak processionary moth by applying chemical pesticides or a spray mixture enriched with the bacterium Bacillus thuringiensis, which are sprayed by helicopter over large areas or on individual trees on the leaves of trees that are infested or threatened by infestation. These methods are effective, but also pose serious environmental risks. This not only affects the caterpillars of the oak processionary moth, but also other butterfly caterpillars as well as breeding birds - the latter not only because of the toxins, but above all because of the subsequent lack of food. Environmental groups therefore advocate gentler methods such as suction.

    features

    The oak processionary moth (lat. Thaumetopoea processionea) is a nocturnal butterfly from the toothed moth family (lat. Notodontidae). The adult moth is quite inconspicuous, but can be easily recognized by the following features:

    body characteristics/gender male moth female moth
    wingspan 25 to 32mm 30 to 36mm
    coloring forewings glossy ash to brown-grey with two dark transverse bands edged with whitish darker colored than the male with little to no markings
    Hind wing coloring yellowish-white with brownish arcuate line and dark spot, fringed off-white, fringed
    abdomen grey-black haired grey-black hairs, blunt end
    particularities Wings can be very dark and unmarked Wings can be very dark and unmarked

    The adult animals fly between the end of July and the end of August. The caterpillars, on the other hand, look quite different depending on the stage. They go through a total of six different stages up to pupation, but have long and very easily broken poisonous hairs right from the start. The animals hatch between April and early May and migrate to the treetops every evening to feed at night. Whole processions up to ten meters long - hence the German name - can be trained with up to 30 animals next to each other.

    digression

    Risk of confusion with the harmless spider moth

    The white webs of the oak processionary moth, which are often found on tree trunks or in branch forks, resemble the white nests of the various web moths. However, in contrast to the oak processionary moth, these are completely harmless. You can recognize a spider moth nest by these characteristics:

    • spread: Web covers whole trees and bushes
    • Preferred shrubs: bird cherry, willow, poplar, hawthorn, euonymus, sometimes fruit trees
    • appearance of the caterpillars: yellowish with black dots, completely glabrous
    • Danger: Infested trees sprout again in the same summer due to the rapid pupation

    The nests of the oak processionary moth, on the other hand, are locally limited to the trunk of the infested tree, and other tree species are usually affected than those of the spider moths.

    distribution and habitat

    Climate change is to blame for the massive proliferation of the oak processionary moth. Originally native to southern Europe, the dangerous caterpillars have now spread to northern Germany.

    The oak processionary moth is originally native to the Iberian Peninsula, i.e. Spain and Portugal, from where it began its campaign of conquest across southern and central Europe to southern Russia and even northern Europe a few decades ago. Caterpillars and moths are now even native to northern Germany and southern Sweden.

    In Germany, all federal states are affected, but particularly densely wooded lowland regions in Berlin and Brandenburg, Baden-Württemberg, Bavaria, North Rhine-Westphalia and Saxony-Anhalt are characterized by mass occurrence. The animals prefer forests rich in oaks, especially pine forests with oaks and oak-hornbeam forests. However, they also occur on individual trees, for example in parks, on roadsides or on avenue trees. The oak processionary moth prefers dry and sunny locations.

    biology and way of life

    The inconspicuous, small moth swarms mainly between July and August, but can still appear in September. Then the females lay up to 300 eggs within a few days, preferably on branches in the crown area of the trees on the warm south side. This is where the so-called egg caterpillar overwinters, surviving frost down to minus 29 degrees Celsius without any problems. The eggs, which are about one millimeter in size, are well camouflaged by a brownish glandular secretion.

    hatching time of the larvae

    As soon as the oak leaves sprout in April and May of the following year and the spring is warm and dry, the caterpillars hatch. These are initially brown-yellow in colour, but change their color to grey-black as they develop. Altogether, the caterpillars of the oak processionary moth pass through six different larval stages within the nine to twelve weeks before they pupate.

    Young caterpillars in the first and second stage do not yet have any dangerous stinging hairs, because these only develop in the third larval phase. From here the caterpillars can be easily recognized by the long caterpillar hairs sticking out in bundles. However, these are non-toxic for humans and animals, because the actually poisonous stinging hairs are very short and only 0.1 to 0.2 millimeters thin. They are only repelled when threatened. A single fully developed oak processionary caterpillar has up to half a million of these poisonous stinging hairs.

    nest building

    Finally, in June, the caterpillars of the oak processionary moth build their typical web nests. These are mostly found on the trunks of oaks, but sometimes also in the forks of branches. The animals need the nests for moulting. The caterpillar nests fill up over time with old larvae skins and faeces and can eventually grow up to one and a half meters in size.

    However, the caterpillars do not remain there permanently, but migrate in several rows into the treetops in the evening and at night, where they feed all night and finally return to their nests at sunrise.

    pupation

    If the animals have eaten enough from the end of June / beginning of July, the pupation process begins. This also takes place in the web nests and lasts between 20 and 35 days. However, the poisonous stinging hairs of the caterpillars remain in the nests, which is why they can be dangerous for people and animals even years later, even without caterpillars.

    hatching time of the moths

    The adult moths of the oak processionary moth finally hatch from mid-August. The differently colored male and female animals immediately begin their mating flight, at the end of which the females finally lay their eggs. The butterfly itself has a very short life expectancy and dies in autumn.

    background

    Warm and dry climate favors mass occurrence

    The oak processionary moth needs a warm and dry climate for its development, which is why it appears in large numbers in years with appropriate springs and summers and after subsequent mild winters.

    Oaks are dying due to massive caterpillar feeding

    Up until about 30 years ago, the oak processionary moth was only found sporadically in Germany, which is why feeding damage was only minor and the affected trees were also able to regenerate well thanks to their strong St. John's sprout. However, this has changed since the 1990s, since the pest now appeared en masse in climatically favorable years.

    A one-off defoliation for the trees in question is basically not that dramatic, as they sprout again. However, it becomes problematic if the oak processionary moth appears strongly for several years in a row. In this case, the ability of the trees to regenerate suffers, they are weakened and susceptible to other pests and diseases such as the oak borer or powdery mildew. As a result, the affected trees no longer grow or show only stunted growth, no longer produce acorns and finally die.

    food plants

    As its name suggests, the oak processionary moth feeds mainly on oak leaves. The pest can basically be found on all types of oak, regardless of whether it is a native sessile or pedunculate oak or the red oak from the USA.In exceptional cases, however, other deciduous trees and occasionally conifers (such as pines) are also attacked.

    frequently asked Questions

    Can the oak processionary moth also be dangerous to pets?

    Dogs in particular are endangered by the caterpillars of the oak processionary moth, as the animals run through the bushes when running free and come into direct contact with the poisonous hair. Although the dog's body is largely protected by its fur, uncovered areas of skin such as the snout and the oral mucosa are at risk - the latter from licking off itchy parts of the body. The same goes for cats, by the way. In principle, the same symptoms can occur as in humans, and the treatment is also the same: wash your pet thoroughly (e.g. in the bathtub or with the garden hose, if necessary let it swim in a lake or stream) and look for one vet up.

    There is a warning sign in our city park. Why should one avoid entering an area infested with caterpillars?

    These warning signs indicate areas contaminated with the caterpillars of the oak processionary moth that should not be entered if possible. The reason lies in the poisonous hairs of the animals, which can sometimes fly for kilometers through the air in windy weather and can thus be inhaled.

    tips

    Nematodes of the species Steinernema feltiae are also effective against the oak processionary moth as long as they are applied in favorable weather and during the second larval stage.

Category:

Animals in the garden