The voracious vine weevil and its larvae are a major nuisance in the garden, as the maggots living underground destroy entire plant populations within a very short time. What really helps against the vine weevil, we have shown in this article for you.

The adult beetles look inconspicuous, but cause a lot of damage

Table of Contents

Show all
  1. the essentials in brief
  2. Fight
  3. damage picture
  4. prevention
  5. way of life
  6. What are vine weevils?
  7. Look
  8. insecticides
  9. frequently asked Questions
  10. Is it true that coffee grounds help against vine weevil?
  11. Does garlic help against the vine weevil?
  12. How can I build a trap myself?
  13. Why does the treatment against the vine weevil not help?

    14. the essentials in brief

    • Vine weevils are best combated by collecting them and/or using nematodes
    • The pests do not like the smell of neem oil
    • Beneficial creatures such as moles, hedgehogs or shrews prefer to eat the insects
    • Insects do not like loose, peaty soil

    Combat vine weevil effectively

    Continuity is important for successfully combating the extremely stubborn pest, because the infestation cannot be contained with a one-off measure. The animals multiply too quickly and too numerously for you to catch them all at once.

    collect

    By manually collecting a vine weevil infestation can be combated quite well. However, you can only catch the nocturnal beetles late in the evening or at night, best during the summer months between May and August. Take a flashlight with you to catch the animals doing their nightly activities - and keep as quiet as possible. Finally, vine weevils perceive the finest vibrations through their leg hairs and flee when danger threatens.

    Incidentally, collecting can be made easier if you place Flaming Katy (bot. Kalanchoe blossfeldiana) right next to infested or endangered plants, which the vine weevil particularly loves. Many of the beetles will migrate to this growth and are easier to catch.

    Control biologically with nematodes

    If the vine weevil infestation is already very pronounced and your plants are plagued by countless larvae, biological control of the animals with the help of nematodes can help. These are tiny nematodes called Heterorhabditis bacteriophora, which you can buy from well-known suppliers such as Bayer or Neudorff in garden shops or simply order from Amazon. Nematodes destroy the vine weevil larvae by invading them and leaving behind bacteria that are deadly to the beetle maggots. The plant is not damaged in the process.

    In order to destroy the larvae in a targeted manner, an exact dosage of the nematodes is necessary. Depending on the square meter treated, you should apply around half a million roundworms. Distribute them as soon as possible after receipt, as the tiny ones die off quickly. However, they usually keep for a few days if you store them in a cool place. Nematodes need moisture to become active. The following video shows how to properly deploy the animals:

    youtube

    The best way to use the roundworms is to follow this scheme:

    1. First water the soil to be treated penetratingly.
    2. Water in the early morning hours of a warm summer day.
    3. Wait until evening.
    4. Pour the nematodes from the packaging into a watering can filled with water.
    5. Stir gently.
    6. Use the mixture to irrigate the root area around the plants to be treated.
    7. Keep the soil area evenly moist for the following weeks.
    8. However, avoid waterlogging, as neither plants nor nematodes tolerate it.

    The application in the dim evening hours is important because the useful animals are very sensitive to UV light. Ideally, the soil should also have a temperature between 15 and 25 °C so that the nematodes feel comfortable in it.

    tips

    There are now also catch boards coated with nematode-containing gel containing the Steinernema carpocapsae species, which you can use to catch and destroy the adult beetles. Simply place the traps under the infested plants between May and September, the beetles will use them as a welcome hiding place during the day and the nematodes will quickly infest them.

    time

    When using nematodes, however, it is not just the manner that is important, but above all the point in time. Most products are only effective at soil temperatures of 12 degrees Celsius and above, which must be maintained over a period of four hours a day. With this in mind, there are two possible treatment periods per year on which the roundworms can work particularly successfully:

    • April May: in the spring you fight overwintering larvae, pupae as well as beetles
    • August September: in late summer the nematodes kill larvae in various stages

    Infested plants in the apartment, on the other hand, can be treated all year round, since there is no frost here.

    Neempress Cake / Neem Oil

    Neem oil, which is obtained from the seeds of the Indian neem or neem tree (bot. Azadirachta indica), is an important pesticide. The natural insecticide contains the substance azadirachtin, which prevents pests from multiplying and thus allows them to die off. The remedy is also very effective against the vine weevil, although you can use neempress cake - these are the residues left over from the production of the oil - for easier application.

    Work this flat into the soil around the plant, repeating this every two months. Count on a consumption of around 50 grams per square meter. The plants absorb the active ingredients from the press cake, so that both the larvae and the adult beetles gradually stop feeding.

    background

    Do not use neem products and nematodes at the same time

    As is so often the case with neem products, what helps against pests often also kills beneficial insects. The ingredients of neem oil are also highly toxic for nematodes, which is why you should not apply the nematodes at the same time as the insecticide.

    Natural enemies

    In principle, every garden owner who has hedgehogs, moles, shrews, common toads or lizards in the garden should be happy: These animals like to eat the adult vine weevil and their larvae and thus keep the population low. If you create refuges and hiding places for these animals, the voracious beetle doesn't stand a chance. Free-ranging chickens also like to scratch for the nutritious larvae, but they cannot be used everywhere in the garden. The poultry not only eats the pests, but also all kinds of vegetables and fruit.

    This is how you recognize a vine weevil infestation in good time

    Because the vine weevil has a wide host range, it quickly eats its way through the garden, infesting a variety of different plant species. However, he has some preferred food plants and nests mainly in rhododendrons, cherry laurel, hydrangeas, roses, berries, yew and bergenia. But many other perennials and shrubs are also on his menu.

    Adult vine weevils leave clear traces

    The feeding damage is also expressed in two ways. The adult beetles feed on the above-ground parts of the plant, while the larvae feed on the roots and other underground parts of the infested crop. The beetle damage is quite easy to recognize, because the adult animals eat veritable bays in the leaf edges. On the other hand, it is much more difficult to identify a larval infestation, because here the damage pattern is quite inconsistent. The table clearly shows you which symptoms indicate a vine weevil infestation:

    stage of development Above-ground damage Subterranean image of damage effects on the plant
    Imago (adult beetle) arched bay damage on the leaf edges, damage to the bark and shoot tips usually none bad condition, little growth, hardly any development, leaf discoloration, wilting
    larva Eating marks on stems and trunk near the ground eroded roots, eroded root collars, debarked roots, hollowed tubers and rhizomes Wilt, stunted growth, leaf discoloration

    If you suspect an infestation with vine weevil larvae on wilted plants, you must look in the root area. Here the small, white maggots are often found in large numbers. It is important to act as quickly as possible when an infestation is identified in order to prevent further damage or even the death of the plant.

    Check potted plants after winter

    Unfortunately, the vine weevil does not only feel very comfortable in the garden, but also in potted plants - regardless of whether they are in the conservatory, on the balcony or in the room. In most cases, an infestation of houseplants and other potted plants is caused by potting soil contaminated with eggs and/or larvae. You should therefore carefully check potted plants with the damage symptoms described for any beetle larvae or even adult beetles. Such a check is important, especially when clearing out the winter quarters, in order to prevent further spread in good time.

    Prevention is better than fight

    So that you don't have a problem with the vine weevil in the first place, you should prevent an infestation. A few measures that make life difficult for the pest and therefore can hardly multiply help here:

    • Avoid potting soil containing peat in potted plants
    • Often work the garden soil gently with a hoe or digging fork (do not damage roots!)
    • Carefully digging into the ground with the digging fork is sufficient
    • do without mulching and pull weeds more often instead
    • Keeping chickens - the larvae of the vine weevil like to pick these out
    • Water plants regularly with plant strengthener
    • Tansy or wormwood manure are particularly suitable

    Make and use tansy or wormwood manure

    Plant-strengthening liquid manure can be made from wormwood and tansy

    Tansy and wormwood can be easily used to make non-toxic, but still effective plant strengtheners that not only drive away the vine weevil. Tansy, for example, also helps against aphids, whiteflies and other leaf sap suckers, as well as against downy mildew, which often occurs in the garden. Wormwood, in turn, also helps against rust diseases and mites. Both plants can be found in nature, especially the tansy is often represented in the summer months at the edges of fields and paths and is easy to recognize by the bright yellow button flowers. Collect the flowering herb whole and either use it fresh or dry it as a reserve for later use.

    Production of the plant manure in the step-by-step instructions:

    1. Crush one kilogram of plant matter (leaves, flowers, stems)
    2. Fill this into a plastic bucket.
    3. Do not use a metal container, as undesirable chemical reactions occur here.
    4. Pour 10 liters of cold water over the plant material.
    5. Add a handful of rock flour (€14.13), this binds the smell that develops later during fermentation.
    6. Put the bucket in a dark and warm place.
    7. Cover it with an air-permeable net or similar.
    8. But don't put a lid on it.
    9. Leave the mass to ferment for 10 to 14 days.
    10. Stir the manure daily with a wooden stick.

    The liquid manure is ready as soon as no more bubbles rise or the liquid no longer foams. Now dilute it with water in a ratio of 1:10 and water the endangered plants with it at regular intervals.

    tips

    Instead of liquid manure, a broth also helps very well. Boil 300 grams of fresh or dried herb in a liter of water for half an hour, then strain out the solids. Let the broth cool down, dilute it 1:10 with water and pour or spray the plants with it. The liquid will keep for several months when filled hot in a screw-top jar or a glass bottle that can be closed well.

    way of life and reproduction

    However, the pests are rarely seen, because vine weevils are both nocturnal and fast. The flightless animals are excellent climbers and perceive even the finest vibrations through special hairs on their front legs. As a result, they quickly recognize approaching danger, simply drop to the ground and hide. Even during the daylight hours, the animals spend their time in protective hiding places near the infested plants, preferably in the mulch, in leaves or even buried in the top layer of soil.

    The animals only become active at dusk, when they climb up the plants and feast on the leaves, shoots and buds of herbaceous plants. In contrast to many other insects, adult vine weevils reach a fairly high age and can live up to 12 months.

    development of the larvae

    While the adult beetles show their first signs of feeding as early as spring, the larvae only become active later. In the wild, oviposition takes place quite late between July and October, whereby the female animals do not have to be fertilized. Instead, the pest usually reproduces by parthenogenesis, i.e. by virgin birth. The round, white and very small eggs with a diameter of not even one millimeter are laid in packs near the host plants, with each beetle female being able to lay up to 1000 eggs.

    The larva of the vine weevil resembles a grub

    The grubs, which are quite similar but much smaller, hatch after about three weeks and spend their entire larval phase underground. How quickly (or slowly) these go through the various stages of their development depends heavily on external conditions. These weather conditions are ideal for rapid pupation and thus even faster reproduction:

    • Temperatures between 16 and 27 °C
    • sufficient soil moisture
    • no dryness

    If the weather is favourable, the larval phase lasts only two months, but if the conditions are unfavourable, the pest can remain in this stage for up to 12 months. The maggots easily overwinter outdoors and become active again in spring. There is only one generation per year, with the exception of greenhouse and conservatory cultures: the animals do not take a winter break here due to the favorable temperatures.

    background

    What does the vine weevil do in winter?

    Vine weevils hibernate as adult beetles as well as larvae that have not pupated, primarily in the root area of their host plants, which they visit when autumn temperatures drop. But other hiding places, especially underground, are also possible, for example in a thick layer of mulch or leaves that the gardener has spread to prepare for the winter. Here the beetles fall into a hibernation, from which they only wake up and become active again in April or May - depending on the weather. Frost does not usually bother the animals hidden underground.

    What are vine weevils?

    Vine weevils (lat. Otiorhynchus) are a genus of beetles from the weevil family (lat. Curculionidae), which cause great damage both in agriculture and in hobby gardens. Both the adults, known as imagines, and their larvae have large appetites. While the adult beetles live above ground and feed mainly on leaves, young shoots and buds, the grubs are in the ground and eat roots, rhizomes and tubers there.

    species

    The genus of the vine weevil is very species-rich and includes about 1000 different species. The ridged vine weevil (lat. Otiorhynchus sulcatus) is the most common pest in our garden. The species is little specialized in certain plant species. In addition, the following species not only make life difficult for the gardener:

    kind Scientific designation distribution Characteristics beetle larvae Favorite plants
    Ridged Weevil Otiorhynchus sulcatus originally Europe, now almost worldwide in temperate regions black with brown spots, about an inch long, unable to fly yellowish white, brown head capsule, about 1 cm long, curved little specialized, preferably rhododendron, cherry laurel, hydrangea, yew, euonymus
    Bristly vine weevil Otiorhynchus scaber originally North America, introduced also in Europe spotted brown, about an inch long, unable to fly yellowish white, brown head capsule, about 1 cm long, curved little specialized, preferably rhododendron, cherry laurel, hydrangea, yew
    Small black weevil or strawberry root weevil Otiorhynchus ovatus North and Central Europe, North America, in lowlands black with longitudinal wrinkles and parallel rows of dots, up to five millimeters long whitish, red-brown head capsule, up to six millimeters long, curved Spruces, spruce forests
    Big black weevil Otiorhynchus coecus Low mountain ranges and Alps, mainly Europe black with reddish legs, longitudinal wrinkles and parallel rows of dots, up to one centimeter long whitish, reddish-brown head capsule, up to one centimeter long, curved Spruces, spruce forests
    Lucerne weevil Otiorhynchus ligustici all of Europe, North America up to 12 millimeters in length, great variance in appearance, mostly brown whitish with brown head capsule, up to one centimeter long Vineyards, fields, meadows eat mainly clover and alfalfa

    Due to the great importance of the vine weevil, the article only deals with it, but the different species are very similar in terms of their biology and possible control options.

    Appearance of the vine weevil

    The ridged vine weevil has a beetle-like appearance that has the following characteristics:

    • legs: three articulated pairs of legs
    • elytra: carapace-like, strongly convex
    • coloring: dark to brown, without metallic sheen
    • size: up to 12 mm long
    • Special marks: granular or ridged back, often spotted with yellow or brown
    • trunk: strong, twice as long as wide, lobe-like enlargements
    • larvae: legless, yellowish white, brown head capsule
    • larva size: about one centimeter, hunched posture is typical

    Are there effective insecticides against the vine weevil?

    Toxins in the garden not only kill pests, but also destroy beneficial insects and damage biological diversity.

    Commercially available chemical sprays such as thiacloprid, imidacloprid or thiamethoxam are expressly not recommended for use in the garden, as they not only combat the vine weevil - but, on the contrary, can destroy the sensitive biological balance and cause considerable damage to flora and fauna.

    For example, these agents are held responsible for the death of bees - with the result that fruit trees and other plants that depend on pollination bear little or no fruit. For this reason, refrain from using toxic pesticides such as these, because you have sufficiently effective biological preparations to hand against pests such as the vine weevil.

    frequently asked Questions

    Is it true that coffee grounds help against vine weevil?

    In fact, dried coffee grounds are both a good fertilizer and an old home remedy for vine weevil. Since the remedy is only slightly effective compared to other preparations, you should not rely on it alone.

    Does garlic help against the vine weevil?

    Garlic is also one of the plants that the vine weevil does not like. As a result, you can counteract an infestation with garlic broth or brew just as effectively as with a remedy made from tansy or wormwood. In addition, the remedy helps against many other pests (for example against aphids, thrips or spider mites) as well as against various plant diseases. And this is how you make the broth:

    1. Crush 3 to 5 large, fresh garlic cloves.
    2. Put the garlic in a container.
    3. Pour a liter of hot, but not boiling, water over it.
    4. For hard water, add a splash of fruit vinegar.
    5. Leave the brew in a warm and dark place for 24 hours.
    6. Sieve the brew and fill it up to a liter with water.
    7. Fill it into a boiled, sealable glass bottle or a screw-top jar of the same type.
    8. Water or spray endangered or infested plants with it.
    9. Repeat the application at regular intervals.

    How can I build a trap myself?

    You will make it easier to collect the beetles at night if you build them a trap. To do this, place flower pots filled with wood shavings or thick, well-moistened cardboard directly under the infested plants. During the day, the pests like to use these as a hiding place and can thus be caught in a very targeted manner. Alternatively, rotten, well-soaked boards also help.

    Why does the treatment against the vine weevil not help?

    If, despite repeated treatment, an infestation with the vine weevil occurs again and again, the supposedly ineffective remedy is usually not to blame. Instead, there can be various reasons why the measures were not successful:

    1.) The treatment was not carried out often and/or densely enough, so that some larvae and/or beetles survived and are now diligently continuing to multiply.

    Countermeasure: Repeat the treatment, but this time more closely and over a larger area.

    2.) Beetles and/or larvae have survived in hiding places not covered by the treatment, perhaps even hibernated, and migrated from there.

    Countermeasure: Remove any hiding spots (also plant pots, boxes and the like!) and treat them thoroughly.

    3.) Adult beetles migrated into yours from outside, for example from the neighbor's garden.

    Countermeasure: Treat your plants again and make your neighbors aware of a possible infestation with vine weevils.

    Unfortunately, the fact is that despite the available effective remedies, the vine weevil can appear again and again. In addition, the animals are simply too eager to reproduce and not very well adapted to certain plants for them to be easily killed off. One remaining larva is enough, which pupates the following year and in turn lays 1000 eggs - and the big feeding is underway again.

    tips

    Even if your garden plants seem to wilt for no reason, the vine weevil is not always behind it. Instead, such wilting can have many different causes, which are often due to incorrect care and / or an unsuitable location.

Category:

Animals in the garden