If a brown-beige butterfly flutters around in the garden at the first frost, hobby gardeners are not happy. So late in the year it can only be the winter moth, which causes trees to be bare next spring. Here you can find out what a winter moth is, how it lives and what damage it causes. How to fight the pest with natural means.

The spider-like webs indicate a strong presence of winter moths

Table of Contents

Show all
  1. the essentials in brief
  2. Frostbite briefly explained
  3. Frostbite Wanted Poster
  4. Combat frostbite
  5. frequently asked Questions

    6. the essentials in brief

    • Winter moths are butterflies whose caterpillars can eat entire trees bare in spring.
    • Males capable of flight are beige-brown to ocher-yellow with a wingspan of 20-46 mm. Flightless females are 5-14mm long, brownish-grey in color with short stub wings.
    • Voracious caterpillars are 25-40 mm long, green or russet with stripes that move in a puckering, cat-hump fashion.

    What is a frostbite? - In a nutshell

    Winter moth is a butterfly and a feared pest on fruit trees as well as wild and ornamental trees. The caterpillars feed on leaves, flower buds, young shoots and fruits in spring. Severe infestations result in defoliation. Often only leaf veins, remains of excrement and inedible fruit remain on the affected tree.

    Frostbite Wanted Poster

    In Germany, the winter moth is represented by two species. Small winter moth and large winter moth differ in size and coloration. This applies equally to the butterfly and the caterpillar. Characteristic of both species is a pronounced difference between sexually mature males and females (sexual dimophism). The following profile has the details:

    Characteristics Little frostbite Large Frost Moth
    color mottled beige-brown to gray-yellow ocher yellow, black patterned
    body length 5-7mm 10-14mm
    male wings 20-25mm wingspan 40-46mm wingspan
    female wings Stub (flightless) Stub (flightless)
    caterpillar color greenish with stripes yellowish reddish brown with stripes
    bead length 20-25mm 35-40mm
    Special feature pushing, humped locomotion pushing, humped locomotion
    Egg size/shape 0.3-0.4 mm small, oval 0.4-0.5 mm small, oval
    eggs color pale green, later orange-red pale yellow, later orange-red
    status Fruit Tree Pest forest pest
    botanical name Operophtera brumata Erannis defoliaria

    Small Freeze Moth causes significantly more damage than Great Freeze Moth. Both types are dangerous for a tree. Therefore, please read the following sections for more detailed explanations on appearance, lifestyle and damage in order to recognize an infestation in good time and take effective countermeasures.

    Appearance of Butterfly and Caterpillar (Lesser Frost Moth)

    The small winter moth only grows up to 0.7 cm

    The forewings of the male moth are rounded, grey-brown to beige-brown with dark, wavy transverse lines. Striking are yellowish fringes along the edges of the wings. In contrast, the hind wings are pale yellow in color. The flightless female only has short, brown wing stubs with gray-yellow speckles. The mouthparts are atrophied because a Frostmoth butterfly does not ingest food during its short lifespan.

    The voracious caterpillar is light green with three light vertical stripes and a dark central stripe on its back. A cat's hump when moving is typical of the spanner larva.

    Appearance of Butterfly and Caterpillar (Great Frost Moth)

    With pale ocher forewings patterned with black and edged with rusty brown, a male Great Frosted Moth flaps about at dusk. The wingless, yellowish-brown, black spotted female looks more like a beetle.

    Caterpillars can be admired in different color variants. Red-brown backs with yellowish side stripes are just as common as black-brown coloring with light spots and other varieties.

    digression

    Frost moth caterpillar surprises with skilful gliding

    The frost moth caterpillar is an amazing climber

    Missing wings and humped locomotion do not prevent a winter moth caterpillar from soaring. In fact, every year high-rise balcony gardeners rub their eyes in amazement at the frost moth infestation on their potted plants at dizzy heights. The butterfly caterpillars copied the stroke of genius from young spiders in Indian summer. If an apple tree is crowded, the newly hatched larva spins a long thread and drifts with the wind to new pastures with juicy leaves.

    Destructive way of life

    The name winter moth refers to a rather unusual mating season in late autumn after the first frost. A development is set in motion that can destroy all hopes of a rich harvest on pome fruit trees next spring. Apple trees, sweet cherries and plums in house gardens and allotments are primarily affected by the small winter moth. Large winter moth sets its sights on maple, oak, beech and hornbeam hedges, which it leaves behind as bare skeletons. The following overview brings you closer to the fatal way of life in fast forward:

    • Mid to late October, the butterflies hatch from the pupae in the ground and the males begin to fly
    • Mating females climb up the tree trunk or await the male visit in the crown
    • Oviposition in bark depressions or winter buds
    • Hibernation of the frost-hardy eggs in the dormant state
    • Caterpillars hatch parallel to budding and the beginning of flowering
    • Maturation feeding of the larvae on leaves, shoots and buds

    Frost moth caterpillars weave a small nest of fine threads between the leaves to protect them from predators. From June, at the end of development, the adult larvae rope down to pupate in the ground. The picture below illustrates the chronological sequence of development:

    damage picture

    Caterpillars of both winter moth species feed on buds and young leaves. As early as May, the first damage and bucking green or red-brown larvae in the treetops are unmistakable. In the further course, nest-like webs form between the leaves. Eaten tufts of leaves, stuck together by spider threads, are bad to look at. The damage threshold on the way to defecating is 4 caterpillars per 100 clusters of flowers or leaves. It starts with pitting and ends with sad leaf skeletons.

    If caterpillars are still present in the fruit tree at the time of fruiting, they will attack apples, cherries and plums. Typical damage is the so-called spoon damage, half of a fruit that falls off prematurely or is unappetizingly corked.

    Combat winter moths naturally - overview

    Glue rings protect trees from frost moth infestation

    The renunciation of chemical insecticides in the natural garden does not mean that you are defenseless against a winter moth infestation. In fact, you can effectively fight the pests with natural means. The following table provides an overview:

    combat medium application When?
    Mechanically glue ring wrap around the tree trunk September to May
    home remedies caterpillar glue spread on stem bark September to April
    Natural enemies parasitic wasps settle outside in spring from 15° Celsius
    predators birds, chickens attract, let loose in the spring
    crop protection products Neem as a spray spray tree 10 days before flowering begins

    The correct procedure for the application is explained in more detail in the following sections:

    Glue ring protects apple tree - how it works

    The glue ring is a band of paper or plastic coated with a tough glue that doesn't dry. Properly attached, a glue ring prevents female winter moths from crawling up the trunk and laying their eggs. How to apply the control agent:

    1. The best time is at the end of September
    2. Choose as smooth a spot as possible at a height of 50 cm on the trunk
    3. Cut glue ring (trunk diameter plus 3-5 cm overlap)
    4. Lay the strip with the side not glued around the tree trunk
    5. Remove protective film, stick and press on
    6. Additionally fix with coated wire at the top and bottom
    7. Important: Remove the glue ring in May at the latest, when the trunk begins to grow thicker

    If there is a support pole at the side of the tree, also attach a glue ring to it. Regularly remove clinging leaves that cunning winter moth females use as a bridge. Please take this opportunity to check the tight fit in order to replace the glue ring if necessary.

    You can find out how a glue ring works as a natural protection against winter moths on apple trees in the following video:

    youtube

    Make caterpillar glue yourself and apply it

    Caterpillar glue has proven itself as a home remedy against winter moths in the home garden. If the adhesive is applied directly to the bark, it is guaranteed that no loopholes can form under whose protection females lay their eggs. Furthermore, caterpillar glue can remain on the tree all year round because no fastening material can constrict the trunk. The following recipe is suitable for the production of caterpillar glue for 10 trees:

    1. Heat 700 g wood tar and 500 g tree resin (rosin) in a water bath while stirring constantly
    2. Stir in 300 g fish oil or vegetable oil
    3. Stir the mixture until it cools down
    4. Apply at the end of September/beginning of October
    5. Apply caterpillar glue at a height of 50-80 cm as a 20 cm wide and 2 mm thick ring

    During preparation, dose the fish or vegetable oil so that a tough, sticky mass is formed that does not drip.

    settle parasitic wasps

    Ichneumon wasps (€22.99) should be given living space so that they can remain in the long term and keep winter moths away

    Natural enemies of the winter moth are parasitic wasps, spiders and ground beetles, which like to be found in natural gardens. If the number of pests gets out of hand, the population of beneficial insects is not sufficient to stop the voracious caterpillars. Clever hobby gardeners settle additional parasitic wasps in the garden because the filigree insects achieve considerable control success. Ichneumon wasps parasitize frost moth caterpillars, which die off within a short time. The hard-working little helpers are bred in special farms, which the squadrons deliver to your home.

    1. Order parasitic wasps in spring when outside temperatures exceed 15° Celsius
    2. On the day of delivery, hang tubes with live parasitic wasp larvae in the plant
    3. Leave tubes hanging for at least 10 days so that all beneficial insects hatch and fly out

    Offer the helpful insects living space in the garden so that they don't wander off again after the work is done. A thick branch with small holes serves as a parasitic wasp hotel. Wild flowers and mixed flowering hedges invite parasitic wasps to feast on the nectar and linger.

    tips

    Ichneumon wasps are masters of multi-tasking. First, all winter moth caterpillars and codling moth larvae are parasitized. The beneficial insects then turn to other pests in the garden. The genus Aphidius colemani prefers to target aphids. A single female parasitic wasp kills up to 200 lice in her short life.

    Predators versus Frost Moths

    For birds, the late flight and mating season of winter moths is a welcome opportunity to fill their stomachs before the harsh winter. Flying males and crawling females spice up the meager diet of numerous garden birds. If there are pecking chickens in the garden, the hatched butterflies have a bad hand when they crawl out of the ground.

    Use the organic pesticide neem correctly

    Neem does not kill the caterpillars, but prevents them from reproducing

    The Indian neem tree (Azadirachta indica) is a global role model in the production of plant defenses. Its main ingredient, azadirachtin, performs excellently as a biological pesticide against winter moths, aphids, box tree moths, lily beetles or the dreaded Colorado potato beetle larvae. On the other hand, there is no effect against codling moths.

    The neem active ingredient is spread over the entire plant as a spray. A frost moth caterpillar absorbs the agent through the body and food. Within a few days, azadirachtin interrupts the development of the larva and stops feeding. No pupation takes place and the vicious cycle of reproduction is stopped. Please note the following when using:

    • No immediate effect: Apply funds in good time, ideally 10 to 14 days before the start of the flowering period
    • Complete wetting: Spray all over the tree, especially the upper and lower sides of the leaves
    • note the temperature: Use neem remedy at temperatures below 25°C
    • Cloudy weather: Only apply organic products in direct sunlight

    Organic pesticides with neem achieve maximum control success when the early stage of a winter moth caterpillar is hit. Against an adult butterfly, the power is only small. The product is available from specialist retailers under various trade names, such as Bio-Pest-Free Neem from Bayer, Naturen Bio-Pest-Free Neem or Insect-Free Neem from Compo.

    frequently asked Questions

    A glue ring cannot be attached to our apple tree because the bark is particularly cracked. What to do?

    We recommend coating the trunk with caterpillar glue to protect against female winter moths. You can make the glue yourself or buy it ready-made. A tried and tested product is Raupenleim Grün from Schacht. Apply the glue as a ring 20 centimeters wide and 2 millimeters thick at a trunk height of about 50 centimeters.

    Are winter moths always harmful to a tree?

    No. Serious damage to trees only occurs when there is a large number of infestations. In fruit growing, the damage threshold is when 3 to 4 caterpillars cavort on the tree for every 100 clusters of leaves or flowers. On plum and apple trees, the damage threshold increases to 10 to 15 caterpillars. A lower number of caterpillars also causes leaf loss, which a healthy tree can cope with without any problems.

    What kind of damage do winter moths cause on apple trees?

    In the spring, the caterpillars eat the pistils and stamens of flowers, which then cannot develop. The leaves are partially glued together and spun into a nest. Initial pitting worsens over time to defoliation down to the leaf veins. Young apple fruits are also damaged because the caterpillars eat the pulp.

    tips

    Biological pest control takes time to be fully effective. What to do when it's too late for glue rings, natural enemies, or neem spray? Under these circumstances, hobby gardeners who are close to nature resort to a biocide based on the bacterium Bacillus thuringiensis. The spray is not chemical, is gentle on beneficial insects and destroys winter moth caterpillars within a few days.

Category:

Animals in the garden