Profile, characteristics and control methods

the essentials in brief

• Frost wrench are butterflies whose caterpillars can eat whole trees bare in spring.
• Flying males are beige-brown to ocher-yellow with a wingspan of 20-46 mm. Flightless females are 5-14 mm long, brownish-gray in color with short wing stumps.
• Gluttonous caterpillars are 25-40 mm long, green or rusty brown with stripes that push themselves like a cat's hump.

What is a frost wrench? - In a nutshell.

Frostspanner is a butterfly and a dreaded pest on fruit trees as well as wild and ornamental trees. The caterpillars feed on leaves, flower buds, young shoots and fruits in spring. In the case of severe infestation, it comes to baldness. Often only leaf veins, remains of excrement and inedible fruits remain on the affected tree.

Frostspanner profile.

In Germany there are two types of the frost spanner. Small Frost Spanner and Large Frost Spanner differ in terms of size and color. This applies equally to the butterfly and the caterpillar. A distinctive difference between sexually mature males and females (sexual dimophism) is characteristic of both species. The following profile has the details:

Small frost wrench causes significantly greater damage than large frost wrench. Both species are dangerous to a tree. Therefore, please read more detailed explanations of appearance, lifestyle and damage in the following sections in order to recognize an infestation in good time and to take effective countermeasures.

Appearance of butterfly and caterpillar

The front wings of the male moth are rounded, gray-brown to beige-brown with dark, wavy transverse lines. Yellowish fringes along the wing edges are noticeable. In contrast, the hind wings are pale yellow in color. In the flightless female, only short, brown wing stubs can be seen with gray-yellow speckles. The mouthparts are stunted because a frost wrench butterfly does not eat any food during its short lifetime.

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

Appearance of butterfly and caterpillar (large frost wrench)

With pale ocher yellow, black patterned and rust-brown lined forewings, a male Great Frostworm flutters around in the twilight. The wingless, yellowish-brown, black-spotted female is more reminiscent of a beetle in appearance.

Caterpillars can be admired in different colors. Red-brown back with yellowish side stripes is just as common as black-brown coloring with light spots and other varieties.

Digression

Frostworm caterpillar surprises with skilful gliding flight

Destructive way of life

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

• In mid / late October the butterflies hatch from the pupae in the ground and the flight time for males begins
• Mated females climb on Tree trunk up or await a visit from men in the crown
• Laying eggs in bark depressions or winter buds
• Wintering of the frost-hardy eggs at rest
• The caterpillars hatch parallel to the shoot and the beginning of the flowering period
• The larvae feed on leaves, shoots and buds as they mature

To protect against predators, caterpillars weave a small nest between the leaves made of fine threads. From June, at the end of development, the adult larvae abseil down to pupate in the ground. The picture below illustrates the development over time:

Damage image

Caterpillars of both species of Frostworm feed on buds and young leaves. As early as May, the first damage and the crouching green or red-brown larvae in the treetops cannot be overlooked. In the further course, nest-like webs form between the leaves. It is bad to look at eaten tufts of leaves, stuck together by spider threads. The damage threshold on the way to baldness is 4 caterpillars per 100 flower or leaf clusters. It starts with pitting and ends with sad leaf skeletons.

If caterpillars are still present in the fruit tree at the time of fruit formation, they attack apples, cherries and plums. Typical damage is what is known as spoon damage, on one side of a fruit that falls off prematurely or corks unsavory.

Fighting frost-wrackers naturally - overview.

Not using chemical insecticides in the near-natural garden does not mean that you are defenseless against frostbite. In fact, you can effectively control the pests using natural means. The following table gives an overview:

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

Glue ring protects apple tree - this is how it works

The glue ring is a tape made of paper or plastic coated with a tough adhesive that does not dry. When properly attached, a glue ring prevents females from crawling up the trunk and laying their eggs. How to apply the pesticide:

1. The best time is at the end of September
2. Select the smoothest possible spot on the trunk at a height of 50 cm
3. Cut the glue ring to size (trunk diameter plus 3-5 cm overlap)
4. Place the strips with the non-glued side around the tree trunk
5. Peel off protective film, stick on 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 thick

If the tree has a support post, attach a glue ring to it as well. Regularly remove clinging leaves that crafty frostworm females use as a bridge. On this occasion, please check the tight fit in order to replace the glue ring if necessary.

You can find out in the following video how a glue ring works as a natural protection against frost tension on the apple tree:

Make and apply bead glue yourself

As a home remedy against frost tension, caterpillar glue has proven itself 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 making caterpillar glue for 10 trees:

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

When making it, dose the fish or vegetable oil so that it creates a tough, sticky mass that does not drip.

Establish parasitic wasps

Are natural enemies of the frost wrench Parasitic wasps, Spiders and ground beetles that like to hang out in the natural garden. If the number of pests gets out of hand, the population of beneficial insects is insufficient to put a stop to 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 helpers are bred in special farms that the squadrons deliver to your home.

1. Order parasitic wasps in spring when the outside temperature exceeds 15 ° Celsius
2. On the day of delivery, hang tubes with living parasitic wasp larvae in the plant
3. Let the tubes hang 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 do not migrate again after their work. A thick branch with small holes serves as a parasitic wasp hotel. Wildflowers and mixed flower hedges invite parasitic wasps to feast on nectar and linger.

Predators versus frost wrenches

For birds, the late flight and mating season of the frost-wrench is a welcome opportunity to fill their bellies again before the harsh winter. Flying males and crawling females spice up the barren menu on 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 organic pesticide neem correctly

The Indian neem tree (Azadirachta indica) serves as a role model worldwide in the production of plant-own antibodies. Its main ingredient, azadirachtin, does an excellent job as a biological pesticide against frostbite, aphids, boxwood moths, lily beetles or the dreaded ones Colorado beetle larva. On the other hand, there is no effect against Codling moth.

The neem active ingredient is distributed over the entire plant as a spray. A Frostworm caterpillar ingests the drug through its body and food. Within a few days, azadirachtin interrupts the development of the larva, combined with a feeding stop. There is no pupation and the vicious cycle of reproduction is stopped. Pay attention to the following when using:

• No immediate effect: Apply funds in good time, ideally 10 to 14 days before the start of flowering
• Complete wetting: Spray the entire tree, especially the top and bottom of the leaves
• Note temperature: Use neem means at temperatures below 25 ° C
• Overcast weather: Only apply organic products in direct sunlight

Organic pesticides with neem achieve maximum control success when the early stage of a frost-wrench caterpillar is hit. It has little impact against an adult butterfly. The product is available in specialist shops under various trade names, such as organic pest-free neem from Bayer, Naturen organic 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 it from females. You can make the glue yourself or buy it ready-made. A tried and tested product is Schacht's green caterpillar glue. Apply the glue as a 20 centimeter wide and 2 millimeter thick ring at a stem height of about 50 centimeters.

Are frost worms always harmful to a tree?

No. Serious damage to trees can only be complained of 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 leaf or flower clusters. On the 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 does frost-wrenching cause on the apple tree?

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