Web moths - species, way of life and enemies

the essentials in brief

• The damage caused by the web moths is rather moderate and usually disappears again after the second leaf shoots
• 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 pruning

Pests or useful?

Web moths are tree pests, as they sometimes occur in large numbers and it is not uncommon for them to bare entire trees. In general, there is no danger to the infected trees from the web moths, because they usually pupate before the second leaf shoots. Many trees and bushes will start forming leaves again after June 21st, so that no trace of the original damage can be seen. An ecological benefit of butterflies and caterpillars is that they provide food for other animals.

also read

• What is the web moth doing on the bird cherry?
• Common wasp - way of life and sensitive handling
• Everything about house crickets: way of life, breeding and control

Beware of permanent infestation of fruit trees:

• Mass reproduction when natural enemies are absent
• Fruit plants are thrown off
• already developed fruits reach smaller sizes
• reduced resistance to environmental influences

Web moths do not damage the tree, even if they often devour entire stands. In late summer, the ghost is over again.

Are web moths poisonous?

Neither butterflies nor caterpillars are poisonous or dangerous for pets and humans. They specialize exclusively in plants and, unlike the oak processionary moth, have no poisonous stinging hair. This butterfly goes through similar developmental cycles and exhibits comparable ways of life as the web moths. However, the stinging hairs can cause itching and severe allergies.

The oak processionary moth does not develop webs. The caterpillars live gregariously in unprotected gatherings to go for food. There are also other differences between the web moth and the oak processionary moth that are easily recognizable.

Oak processionary moth profile:

• Fore wings glossy ash to brownish gray with two transverse bands
• Hind wings darkly fringed, yellowish-white and greyish pollinated
• Caterpillars with a dark back line, velvety hairy fields and red-brown, long-haired warts

What can be done against web moths?

Remedies against web moths have an extremely limited period of action. If the caterpillars have already developed webs, spraying won't do much. The fine structures are so dense that no droplets can get inside. Pesticides are only effective when the egg caterpillars leave their nest 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 gets into the digestive tract. Here it unfolds its poisonous effect for the larvae. The caterpillars stop eating and perish. You will only be successful if you use agents containing this bacterium between mid-April and mid-May. The caterpillars are only susceptible in the first larval stage.

Use sprays only in an emergency

A chemical-based control agent usually does not work selectively, but also damages beneficial insects such as ladybugs or ear peasants. In the case of infested apple trees, sprinkling is recommended. The tree is completely treated with an agent that contains paraffin oil. However, the period of application plays an important role. If you inject too early, the caterpillars are still in the resting phase and are protected by their shield. A late spraying damages the tree if it is already in the bud.

Approved sprays for ornamental trees:

• Organic pest free neem
• Calyso pest-free
• Caterpillar-free XenTari (for apple trees)

Get rid of it naturally

You should prefer biological control so that you don't cause additional damage. As the trees usually recover, targeted control is usually not necessary. Instead, see to it that the natural enemies in the garden are encouraged. If the caterpillars reappear every year, some measures will help you.

Collecting

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. Before doing this, put a cloth under the wood so that you can then remove the caterpillars. To prevent the overlooked caterpillars from crawling back up the tree, you should provide the trunk with glue rings. The caterpillars stick to it and perish.

Other methods:

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

Hot water

To save the caterpillars an agonizing death from a 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 protected egg layers that you can scrape off the trees before winter.

Pheromone trap

You can buy attractant traps in stores that contain special pheromones. The butterflies fly into the trap and stick when they settle on the glued surfaces. This prevents the mating of the animals, so that the number of eggs is reduced. Since 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 fragrances that emanate from the host plants. Once they have sniffed the right plant, they sit down on the leaves. The males also use their sense of smell to track down a female capable of mating. This secretes a pheromone to draw attention to itself.

Pruning

If you've noticed an infestation in summer, you should prune the tree back just before winter. Check the branches for egg clutches and overwintering caterpillars. The clippings should not be disposed of on the compost, but rather brought to the nearest waste disposal facility.

Tips

Infested branches can also be cut off during the summer, provided the webs have not yet covered the entire tree.

Natural regulation

Web moths have no advantage if they reproduce en masse. If the weather conditions lead to uncontrolled spreading, natural opponents quickly emerge. They contain the stocks and thus ensure a natural balance. If some kind has enemies, a plague is automatically prevented. Chemical pest control is therefore necessary in a few cases.

Scarce food resources

As more and more caterpillars develop, the food supply becomes increasingly scarce. It comes 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 hunger females. They are smaller than normal females and have limited fertility. The further reproduction of the moths is then increasingly restricted.

Diseases

Particularly large populations are also contained by parasites and pathogens. These natural enemies only appear when the caterpillar populations have already expanded en masse. If high humidity develops in the overpopulated webs, viruses and diseases spread. Roundworms and fungi are also involved in the natural regulation of the web moth. If such pathogens are picked up in the last phase of development, the caterpillars die within a few days.

This is how a virosis 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 web moth occurs on the bird cherry. Occasionally synonyms are also used, as the moths have several trees in their sights. The plum web moth is sometimes referred to as the sloe web moth. Four species are particularly common in gardens.

	Host plants	Forewing	habitat	Scientific name
Pfaffenhütchen web moth	Pfaffenhütchen, Japanese spindle bush	white, fringed	Biotopes with calcareous soils	Yponomeuta cagnagella
Apple web moth	Crab apple, cultivated apple	White	Orchards	Yponomeuta malinellus
Plum web moth	Sloe, hawthorn, hawthorn, plum, cherry	greyish-white	almost all biotopes with host plants	Yponomeuta padella
Bird cherry web moth	Common bird cherry, rarely cherry or buckthorn	silvery white	Alluvial forests, brook banks with bushes and trees, gardens, parks	Yponomeuta evonymella
Hawthorn moth	Hawthorn, hawthorn, cotoneaster, sloe, apple	white with brown stripes	Shrub borders, gardens	Scythropia crataegella

general characteristics

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

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How to recognize web moths

Adult moths often have white fore wings that are black or darkly spotted. The hind wings appear gray. Web moths have a wingspan of up to 25 millimeters. The shape of the butterflies when they have closed their wings is typical. These are reminiscent of a steep roof.

Unique web:

• consists of innumerable wafer-thin threads
• can be peeled off in long strips
• has an extremely high tear resistance
• Damages are 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 seen on plants from 50 different families. They mainly colonize sweet grasses and deciduous trees. More than 80 percent of food consumption 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. Insectivorous songbirds are among the most important predators. A pair of titmice feed around 10,000 different species of caterpillars to the offspring. Birds not only hunt larvae, they also prey on adult moths.

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

	Eischmarotzer	Larvae, pupae parasites	specialized in web moths
Ore wasp	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 a tile-like 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 stages before turning into a full-grown butterfly. Their size grows with each larval stage and the color changes too.

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 has a light gray to cream-colored tint. It hibernates under its protective shield in the first larval stage and then leaves its home in the next spring. Then the caterpillars start to eat. To protect themselves from rain and predators, they build a fine web. The animals live here socially, so that sometimes hundreds of larvae can be observed in a web. The webs are increasingly widened and in the final stage are reminiscent of a white veil. Because of these veil-like structures, the moths got their common German name.

Transformation into a butterfly:

• Eating is stopped four to five days before the last pupation
• 20 millimeter long caterpillars pupate
• Cocoons hang vertically in the dense web of gathering
• after ten to 20 days the butterfly hatches

Where web moths occur

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

Preferred plant families

Plum, apple and bird cherry web moths are responsible for infesting fruit trees such as cherry or apple trees. While these species can be found mainly on rose plants, the willow web moth only inhabits willows. In addition to the eccentric spider moth, the buckthorn spider moth can also be found on spindle bushes. The Sedum web moth lives on thick-leaf plants. Usually there are no web moths in the apartment.

• Rose plants : apple, plums or plums, cherries, rock pears, grapes, hawthorn, sloe, bird cherry
• Spindle family : Euonymus europaeus
• Willow plants : white willow, osier, sallow willow, gray willow
• Thick-leaf family : large butterwort

Mass appearance

It is 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. 2017 was such a year. In the Berlin Hasenheide and on the Olchinger See numerous trees and bushes were covered by the fine veils, which aroused fear in the people.

weather

Particularly mild winter months with little snow promote the survival of caterpillars in the first larval stage, which overwinter under their hardened protective shield. When the summer months are particularly hot and dry after wintering, there is increased sexual activity in the adult moths.

This prevents mass reproduction:

• periods of heavy rainfall
• night temperatures below twelve degrees Celsius
• windy conditions

Garden close to nature

Web moths often appear where the habitat is very one-sided. Alleys 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.

Pile of stones

Cold-blooded lizards feel particularly comfortable when they find sunny spots in the garden. They need cracks and crevices into which they can withdraw in case of danger. Lizards feed on various insects, so that web moths also end up in their stomachs.

Wild trees

It is true that sloe, hawthorn and rock pear offer optimal feeding conditions for some web moths. Birds also feel at home in wild-growing hedges, as they find a real treat in the caterpillars and butterflies. Make sure that the hedges consist of different types of wood.

Tips

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

frequently asked Questions

How old do web moths get?

Adult females have a lifespan of around 60 days. The males die after mating. The caterpillars hatch in the same year and hibernate before turning into a full-grown butterfly in the following year.

Why do web moths eat mainly in June?

At this time, the caterpillars are in the fifth instar. The leaves are still tender enough and contain a particularly large amount of nitrogen compounds. These are easy to use and provide the caterpillars with important nutrients.

Do web moths harm the tree?

Although the caterpillars can eat trees completely bare, healthy woody plants quickly recover from the leaf damage. The caterpillars produce large amounts of feces that fall to the ground and are quickly broken down 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 web moths have to be fought?

In many cases it is not necessary to control the moths. Nature itself has developed mechanisms to counteract mass spread. Rainy summer months and high humidity are harmful to the insects. If the caterpillars appear en masse, no chemical agent will help. The spook ends automatically after the summer months. Frosty temperatures in winter mean that many egg caterpillars freeze to death.

Do I have to report web moths?

If you discover a tree infestation that is the result of the web moth, there is no need to worry. The insects do not have to be reported, as their populations are regulated by natural opponents. However, the oak processionary moth should be reported, as its caterpillars have poisonous hair.