Many trees are completely covered in a white web in summer. For some people, this phenomenon looks spectacular. Other nature lovers fear a plague. The reason for this fear is the poisonous oak processionary moth. However, the spider moths have little in common with this species.

Web moths build beautiful webs, but unfortunately cause a lot of damage

Table of Contents

Show all
  1. the essentials in brief
  2. Pests or useful?
  3. Spider moth poisonous?
  4. Fight
  5. Get rid of course
  6. Natural regulation
  7. species
  8. Characteristics
  9. development
  10. habitat
  11. Mass appearance
  12. Natural garden
  13. frequently asked Questions

    14. the essentials in brief

    • The damage caused by the spider moths is rather moderate and usually disappears again after the second leaf sprouting
    • Web moths are not poisonous; quite the opposite of the oak processionary moth, which, however, does not form webs
    • An infestation can be contained with pheromone traps, by collecting or by cutting back

    Pests or useful?

    Web moths are considered tree pests because they sometimes occur in large numbers and often eat entire stands of trees bare. In general, there is no danger from the spider moths for the infested trees, because they usually pupate before the second leaf shoots. Many trees and shrubs shed their leaves again after June 21st, so that there is no trace of the original feeding damage. One ecological benefit of moths and caterpillars is that they provide food for other animals.

    Caution with permanent infestation of fruit trees:

    • Mass reproduction in the absence of natural enemies
    • Fruit plants are discarded
    • already developed fruits reach smaller size
    • reduced resistance to environmental influences

    Web moths do not damage the tree, even though they often bare whole stands. In the late summer the spook is over again.

    Are spider moths poisonous?

    The spider moth is not poisonous

    Neither moths nor caterpillars are poisonous or dangerous for pets and humans. They have specialized exclusively in plants and, unlike the oak processionary moth, have no poisonous stinging hairs. This butterfly goes through similar development cycles and exhibits comparable lifestyles to the spider moths. However, the stinging hairs can cause itching and severe allergies.

    The oak processionary moth does not develop webs. The caterpillars live socially in unprotected assemblages to go for food. In addition, there are other differences between the spider moth and the oak processionary moth that are easily recognizable.

    Characteristics of the oak processionary moth:

    • Forewings glossy ash to brown-grey with two transverse bands
    • Hind wings darkly fringed, yellowish-white and dusted with greyish
    • Caterpillars with a dark topline, fields velvety hairy and red-brown, long-hairy warts

    What to do against spider moths?

    Means against spider moths have an extremely limited period of action. If the caterpillars have already developed webs, spraying will not do much. The fine structures are so dense that no droplets can get inside. Pesticides are only effective if the egg caterpillars leave their clutch and crawl freely on the wood.

    Bacillus thurigiensis

    This bacterium proves to be an effective control agent against spider moth larvae. They ingest it with their food so it enters the digestive tract. Here it unfolds its poisonous effect on the larvae. The caterpillars stop eating and die. Success can only be seen if you use funds with this bacterium between mid-April and mid-May. The caterpillars are only susceptible in the first larval stage.

    Only use sprays in an emergency

    A chemical-based control agent usually does not act selectively, but also damages beneficial insects such as ladybugs or earwigs. In the case of infested apple trees, sprouting spraying is recommended. The tree is completely treated with a product containing paraffin oil. However, the application period plays an important role. If you inject too early, the larvae will still be dormant and protected by their shield. A late spraying damages the tree when it is already in budding.

    Approved sprays for ornamental trees:

    • Organic Pest Free Neem
    • Pest-free Calyso
    • Caterpillar-free XenTari (for apple trees)

    Get rid of course

    You should prefer biological control so you don't do additional damage. Since the trees usually recover, targeted control is usually not necessary. Instead, ensure that the natural enemies in the garden are encouraged. A few measures will help you if the caterpillars reappear every year.

    collect

    Collecting the caterpillars is not particularly time-saving but effective

    The easiest way to combat it is to regularly check for an infestation. Collect the caterpillars as soon as you find them. The fine webs can be swept away with a broom. Place a cloth under the wood beforehand so that you can remove the caterpillars afterwards. To prevent the overlooked caterpillars from crawling back up the tree, you should apply glue rings to the trunk. The caterpillars stick to it and die.

    Other methods:

    • Cut out slightly affected branches
    • Remove thin webs with a hard jet of water
    • Do not dispose of leftovers in the compost but in household waste

    Hot water

    To save the caterpillars an agonizing death from lack of food, you can pour boiling hot water over them. This measure is environmentally friendly and ensures that the caterpillars die immediately. It also destroys the caterpillars in sheltered egg clutches, which you can scrape off the trees before winter.

    pheromone trap

    In stores you can buy attractant traps that contain special pheromones. The moths fly into the trap and stick when they settle on the glued surfaces. This prevents the animals from mating, so that the egg clutches are reduced. Because the pheromones are species specific, you need to choose the right pheromone trap.

    digression

    pairing

    The females look for suitable food plants so that their offspring can find ideal living conditions. They are based on the scents that emanate from the host plants. Once they have sniffed the right plant, they settle on the leaves. The males also use their sense of smell to track down a mating female. This secretes a pheromone to draw attention to itself.

    pruning

    If you have noticed an infestation in the summer, you should prune the tree just before winter. Check the branches for eggs and overwintering caterpillars. The clippings should not be disposed of in the compost, but should be taken to the nearest waste disposal site.

    tips

    Affected branches can also be cut off during the summer, provided the webs have not yet spread over the entire tree.

    Natural regulation

    Web moths have no advantage when they breed in large numbers. If optimal weather conditions lead to uncontrolled spread, natural opponents quickly appear. They contain the stocks and thus ensure a natural balance. If a species has enemies, a plague is automatically prevented. Chemical pest control is therefore necessary in a few cases.

    Nature itself often curbs the infestation of spider moths

    Scarce food resources

    As more and more caterpillars develop, the food supply becomes increasingly scarce. This leads to hunger stress, from which numerous caterpillars die before the last pupation. The caterpillars, which have passed the last stage of development, live as so-called hungry females. They are smaller than normal females and have limited fertility. The further reproduction of the butterflies is then increasingly restricted.

    Diseases

    Particularly large populations are also contained by parasites and pathogens. These natural predators only appear once the caterpillar populations have already expanded en masse. If high humidity develops in the overcrowded webs, viruses and diseases spread. Nematodes and fungi are also involved in the natural regulation of the spider moth. If such pathogens are ingested in the last phase of development, the caterpillars die within a few days.

    This is how a virus manifests itself:

    • The body of the caterpillar swells
    • the larvae burst when touched
    • virus-containing liquid is distributed in the web and causes further infections
    • dry brown masses recognizable

    species

    The German name indicates the preferred host plants of the respective species. This is how the bird cherry spider moth occurs on the bird cherry. Occasionally, synonyms are also common, since the moths have several trees in their sights. The plum spider moth is also sometimes referred to as the sloe spider moth. Four species are particularly common in gardens.

    host plants fore wing habitat Scientific name
    Spindle Tree Moth Spindle Tree, Japanese Spindle Tree white, fringed Biotopes with calcareous soils Yponomeuta cagnagella
    Apple Spider Moth crab apple, cultivated apple White orchards Yponomeuta malinellus
    plum spider moth Sloe, hawthorn, hawthorn, plum, cherry grayish white almost all biotopes with host plants Yponomeuta padella
    Bird cherry spider moth Ordinary bird cherry, rarely cherry or buckthorn silvery white Alluvial forests, stream banks with bushes and trees, gardens, parks Yponomeuta evonymella
    hawthorn moth Hawthorn, hawthorn, cotoneaster, sloe, apple white with brown stripes edges of bushes, gardens Scythropia crataegella

    general characteristics

    Web moths are a family of butterflies that includes around 900 species worldwide. About 116 species occur in Europe, with the typically white moths falling into the lower classification of the Yponomeuta. This genus has no official German name.

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    How to recognize spider moths

    Adult moths often have white forewings dotted with black or dark. The hind wings appear grey. Web moths have a wingspan of up to 25 millimeters. The shape of the butterflies is typical when they have closed their wings. These are reminiscent of a steep roof.

    Unique Weave:

    • consists of innumerable wafer-thin threads
    • can be pulled off in long strips
    • has an extremely high tear resistance
    • Damage will be repaired within a very short time

    food

    Caterpillars feed on plant tissue. They mainly eat leaves and needles from the inside. Some larvae also feed on buds and flowers. The caterpillars can be observed on plants from 50 different families. They mainly inhabit sweet grasses and deciduous trees. More than 80 percent of food intake takes place in the last larval stage, which is lived through in June. During this phase, the caterpillars can eat a tree completely bare.

    Natural enemies

    Web moths are on the menu of various animals. The most important predators include insectivorous songbirds. A pair of tits feeds about 10,000 different species of caterpillars to their offspring. Birds not only hunt larvae, but also capture adult moths.

    The enemies of the spider moths are mainly interested in the proteins, because the caterpillars are extremely rich in protein. Until the protective webs are finished, the larvae are eaten by assassin bugs, wasps and flies. But there are also numerous insects that live parasitically and thus curb the spread of the spider moth.

    egg eater Larval, pupal parasites specialized in spider moths
    Chalwasp x x Yes
    Green lacewing x no
    catchy tune x no
    ants x no
    parasitic wasps x Yes
    caterpillar flies x Yes

    development

    Females lay their eggs in an imbricated arrangement on young shoots and twigs. They cover the clutch with a secretion that hardens quickly and protects the eggs. It takes a few weeks for the first larvae to hatch. A caterpillar goes through four to five instars before turning into an adult moth. Their size increases with each larval stage and the coloring also changes.

    Important appointments:

    • The moths fly between June and August
    • Mating and oviposition from July to August
    • intensive feeding phase from June of the following year

    stages

    The newly hatched larva is light gray to cream in color. She hibernates in the first larval stage under her protective shield, only to leave the dwelling next spring. Then the caterpillars start to eat. To protect themselves from rain and predators, they build a fine web. In it, the animals live sociable, so that sometimes hundreds of larvae can be observed in a web. The webs are increasingly expanded and in the final stage are reminiscent of a white veil. Because of these veil-like structures, the moths got their German trivial name.

    Transformation into a butterfly:

    • feeding is stopped four to five days before the last pupation
    • 20 mm long caterpillars pupate
    • Cocoons hang vertically in the dense collective web
    • after ten to 20 days the moth hatches

    Where spider moths occur

    A prerequisite for the spread of the various species is the existence of their host plants. Each spider moth species has specialized on a host, so that only certain trees or grasses are infested. These occur naturally along the banks of streams and rivers, in hedges or copses and at the edges of forests. Numerous trees and fruit trees grow in gardens or parks, which is why the butterflies can also be found in settlements and cities.

    Preferred plant families

    Plum, apple and bird cherry spider moths are responsible for infesting fruit trees such as cherry or apple trees. While these species are mainly found on rose plants, the willow spider moth only inhabits willows. In addition to the euonymus spider moth, the buckthorn spider moth can also be found on spindle shrub plants. The sedum spider moth lives on succulent plants. Normally, spider moths do not occur in the apartment.

    • rose family: apple, plum, cherry, pear, grape, hawthorn, sloe, bird cherry
    • Spindle shrub plants: Euonymus (Euonymus europaeus)
    • willow plants: white willow, osier, willow, gray willow
    • succulents: Big butterwort

    Mass appearance

    It is becoming more and more common for the webs to cover entire rows of trees and gardens. The caterpillars spin benches and tables or fence posts themselves. 2022 was such a year. In the Berlin Hasenheide and on the Olchinger See, numerous trees and bushes were covered by the fine veils, which frightened people.

    The work of the spider moth definitely has an aesthetic character

    weather

    Particularly mild winter months with little snow favor the survival of caterpillars in the first larvae stage, which hibernate under their hardened protective shield. When the summer months are particularly hot and dry after hibernation, adult moths become more sexually active.

    This prevents mass proliferation:

    • rainy periods
    • night-time temperatures below twelve degrees Celsius
    • windy conditions

    Natural garden

    Web moths often appear where the habitat is very one-sided. Avenues with one tree species and low lawns or orchards with little diversity provide plenty of food for the caterpillars. Make your garden as varied as possible. The more different habitats you create, the more natural enemies will be attracted.

    deadwood

    Dead wood and gnarled roots or tree stumps are an ideal habitat for highly specialized insects. Larvae of various beetles or hymenoptera withdraw into the moist environment that prevails under the rotten bark. Here they are protected from predators and can develop undisturbed.

    cairn

    Cold-blooded lizards feel particularly comfortable when they find sunny spots in the garden. They need crevices and crevices to retreat to when threatened. Lizards feed on various insects, so spider moths also end up in their stomachs.

    wild woods

    Blackthorn, hawthorn and service pear offer optimal feeding conditions for some spider moths. Birds also feel at home in wildly growing hedges, finding a real treat in the caterpillars and moths. Make sure that the hedges consist of different types of trees.

    tips

    Bats also hunt for spider moths. Support the flying mammals with bat boxes and insect flowers.

    frequently asked Questions

    How old do spider moths get?

    Adult females have a lifespan of around 60 days. The males die after mating. The egg caterpillars hatch in the same year and hibernate before turning into adult moths the following year.

    Why do spider moths eat mainly in June?

    At this time, the caterpillars are in the fifth instar larvae. The leaves are still tender enough and contain a particularly large number of nitrogen compounds. These are easily digestible and provide the caterpillars with important nutrients.

    Do spider moths damage the tree?

    Although the caterpillars can eat trees completely bare, healthy trees quickly recover from the leaf damage. The caterpillars produce large amounts of droppings, which fall to the ground and are quickly decomposed there. This makes the lost nitrogen compounds available to the tree, creating a kind of nutrient cycle. An infestation only becomes dangerous if the caterpillars feed on the same tree every year. This weakens fruit trees in particular.

    Do spider moths have to be fought?

    In many cases it is not necessary to control the moths. Nature itself has developed mechanisms to counteract a massive spread. Rainy summer months and high humidity damage the insects. If the caterpillars nevertheless appear in large numbers, no chemical agent will help. The spook ends automatically after the summer months. Freezing temperatures in winter ensure that many egg larvae freeze to death.

    Do I have to report spider moths?

    If you find a tree infestation caused by the spider moth, there is no need to worry. The insects do not have to be reported because their populations are regulated by natural enemies. However, the oak processionary moth should be reported because its caterpillars have poisonous hair.

Category:

Animals in the garden