If beetles are on the move in the garden, they are usually weevils. Some species are up to no good and sometimes cause serious damage. Read this guide to learn how to accurately identify weevils and fight them non-toxically.

Some weevil species lay their eggs in closed buds

Table of Contents

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  1. the essentials in brief
  2. What are weevils?
  3. Identify weevil species
  4. Weevil Species Plant Pests
  5. Biological control of weevils
  6. Biological control of weevils
  7. Weevil in the house
  8. frequently asked Questions

    9. the essentials in brief

    • Weevils have a proboscis-shaped head extension, are 0.3-2 cm in size and dark in colour.
    • Lower classifications as plant pests are vine weevil, apple blossom weevil, strawberry blossom weevil, large brown weevil, cabbage shoot weevil and hazelnut borer.
    • You can successfully fight weevils by collecting them, using traps, nematodes, glue rings and neempress cake. The best remedies against weevils in the house are the flower pot trap and nematodes.

    What are weevils?

    With an impressive 51,000 to 60,000 species, weevils (Curculionidae) are the most species-rich family within the beetle order on our planet. Weevils and lower classifications are becoming unpopular crop pests worldwide. Hardly any plant tissue is spared from the voracious beetles and insatiable larvae. To ensure that the native flora is sufficient for all weevils, numerous species have specialized. Other species are generalists and eat whatever comes in front of their snouts. If there is a high incidence, a weevil plague in agriculture and hobby gardens can destroy the entire harvest.

    Trademark trunk

    The palm weevil is rarely found in Germany

    The name refers to a long snout in the middle of the beetle's face. This is a trunk-shaped extension of the head and not a suction organ. There is a chewing mouthpart at the tip of the trunk. Characteristic are conspicuously kinked antennae sitting on the trunk.

    Central European weevils are a few millimeters to two centimeters in size. The beetle bodies are colored differently, with dark colors dominating in Germany. Some species shine in red, blue or metallic green. Colorful weevils are predominantly native to tropical regions, such as the bright red palm weevil (Rhynchophorus ferrugineus), which has specialized in palm trees in the Mediterranean region. The wings are usually fully developed but not used. Weevils prefer to walk on their six powerful legs.

    Identifying weevils - an overview of common species

    Of the approximately 60,000 weevils worldwide, around 950 species are native to Germany. A number of genera and species cause considerable damage in fields, gardens, forests and parks. Everyone wears the eponymous trunk face. Only on closer inspection do individual distinguishing features reveal themselves. The following table gives important indications for six of the most dangerous weevil species in Germany in order to correctly identify the pest in question:

    Common species vine weevil apple blossom cutter Strawberry Blossom Picker Big brown weevil cabbage weevil hazelnut borer
    size 8-10mm 3.4-4.3mm 2.0-4.1mm 10-14mm 2.5-4.0mm 6-8.5mm
    color mottled black and brown scaled white-brown shiny black-brown grey-brown dotted grey-spotted brown-white scales
    legs thickened in the middle dark brown dark brown dark grey-brown dark grey reddish brown
    elytra heavily rounded Drawn in a V-shape striped yellow striped mottled light grey hairy comb
    botanical name Otiorhynchus Anthonomus pomorum Anthony rubi Hylobius abietis Ceutorhynchus Curculio nucum

    The larva of a weevil is legless, white to off-white in color and has a brown head capsule. A hunched posture is typical, so that weevil larvae are often confused with cockchafer larvae, rhinoceros beetle larvae and other grubs.

    way of life

    Larvae of the apple blossom weevil can be found in apple blossoms in spring

    In early spring, weevils crawl out of their winter quarters. Some species overwinter as larvae or pupae and hatch in spring. Hungry, the beetles pounce on the fresh green to gather strength for the forthcoming mating season. Several species have gotten rid of their males and are capable of virgin birth. A female lays up to 1,000 eggs, from which insatiable larvae hatch within a short time. One generation is passed through each year.

    Most weevils are crepuscular and nocturnal. Only under the cover of darkness do the beetles leave their hiding place and go in search of food. Typical feeding patterns are nibbled leaf edges, drilled buds and broken flower stalks. Depending on the species of weevil, a larva develops inside the plant or in the ground. Mined stems and eroded roots are the result.

    When temperatures drop in autumn, weevils reduce their feeding activity. It overwinters in the ground, under dry autumn leaves or under the cover of tree barks.

    digression

    Bark beetles are weevils

    In German forests, a battle is raging between humans and weevils for every single tree. One of the most dangerous Curculionidae subfamilies, bark beetles (Scolytinae) wreak havoc on trees. Although the distinctive snout of a bark beetle is at best rudimentarily present, botanists categorize the species-rich subfamily as weevils of a lower classification. Hobby gardeners with their own stock of trees are sometimes confronted with the insidious bark beetle subspecies book printer (Ips typographus), a dreaded pest for blue spruce and other magnificent conifers.

    Weevil species as plant pests

    Because weevils tend to be up to mischief at night, a visual inspection is reserved for night owls and early risers among hobby gardeners. It's good to know that the dreaded gang of 6 from the weevil family can't just be identified by their looks. The battered plant species and species-specific behavior act as further indications of which species of weevil is infesting the garden at night and in the fog or is cheekily up to mischief in the house.

    Vine weevil (Otiorhynchus)

    Vine weevils are the most feared in Germany

    The dubious title of “worst weevil in Germany” is given to the weevil. The ridged vine weevil (Otiorhynchus sulcatus) in particular leaves a devastating scene when it invades the garden in large numbers. Adult beetles and larva are not picky. More than 100 plant species are on the menu. With the onset of summer, vine weevils cause the characteristic, semi-circular bay feeding on leaves. At the same time, their maggots in the ground attack the delicate roots. The following plants are particularly affected:

    • Azalea and Rhododendron
    • Yew and Thuja
    • Firethorn
    • lilac
    • cherry laurel
    • cornel
    • rose

    If the favorite shrubs with thick-leaved leaves are not available, the menu is quickly expanded to include herbaceous plants. Flowers and perennials such as cyclamen, asters, hollyhocks, fuchsias, geraniums and begonias are very popular. In addition, vine weevils do not disdain vegetable plants, such as tomato plants or peppers. It doesn't matter to the pests whether the forage plants thrive in the bed, on the balcony or in the apartment.

    Apple Blossom Weevil (Anthonomus pomorum)

    Apple blossom weevils prefer to overwinter in the immediate vicinity of fruit trees in the leaf litter or under the tree bark. The pests become active in good time before the beginning of the apple blossom. From mid-March, the females place their eggs in the swelling buds using a ovipositor. Within a few days, the larvae hatch and hollow out the inside of the bud. The bud continues to grow, but cannot unfold. Pupation takes place in the balloon-like swollen bud, which gradually turns brown. Only when the beetle is fully grown does an apple blossom weevil leave the bud cradle and move its food intake outside.

    Strawberry blossom weevil (Anthonomus rubi)

    The strawberry blossom weevil grows in strawberry or raspberry buds

    Strawberry blossom weevils live up to their name with a sophisticated propagation strategy. At the end of April, the female eats a small hole in each flower and lays an egg in it. The strawberry blossom then snaps off and withers, while the larva fills its stomach inside the bud. After some time of gluttony, the weevil larva pupates, remains dormant for some time and leaves the demolished flower as a finished beetle.

    The prey scheme includes not only strawberry plants, but numerous rose plants. Raspberries, blackberries and roses have to sacrifice their finest flower buds to the insatiable brood of the strawberry blossom stinger.

    Large brown weevil (Hylobius abietis)

    The large brown weevil is also known by the apt name spruce weevil. The stately beetle is widespread in the coniferous forests. On the menu is the bark, which the beetle can easily eat thanks to the powerful chewing tools on its proboscis. Considerable damage occurs under high infestation pressure, whereby young trees can even die. As a result of shrinking habitats, the respectable weevil is forced to invade gardens and parks. The big brown weevil has its sights set on the following tree species:

    • spruces
    • Douglas firs
    • larches
    • Pine trees

    More rarely, the spruce weevil feeds on deciduous trees such as alders or oaks. Its larvae develop in deadwood and newly felled trees, as well as the shallow roots.

    Cabbage weevil (Ceutorhynchus)

    Cabbage weevils particularly like to attack cabbage

    The tiny cabbage shoot weevil can cause major damage in kitchen gardens. The first beetles, which have hibernated in the shelter of a cocoon in the ground, appear at a cool 6° Celsius. After a short maturation period, females lay their eggs in the plant stalks in close proximity to the terminal bud. The flightable weevil species has a wide range of food:

    • All kinds of cabbage
    • Rape, especially winter rape
    • watercress
    • radish
    • horseradish

    The actual damage is not caused by the maturing feeding of adult cabbage shoot weevils. Rather, it is the greedy larvae that bore through the inside of the stem and devour the marrow. In the immediate vicinity of the terminal bud, this process has fatal consequences because growth comes to a standstill. In addition, scientists have found that pricking the stems to lay eggs can transmit various pathogens.

    Hazelnut borer (Curculio nucum)

    The Hazelnut Borer boasts an epically long snout. Evolution has equipped the weevil with this tool so that it can pierce hard hazelnut shells and eat the solid flesh. The weevil owes its reputation as a pest not least to the fact that the adult beetles attack cherries, pears, apples and other fruits in spring. In this way, the pests bridge the time until the first hazels ripen so that females can lay their eggs in the young nuts.

    Fight weevils - This is how it works without poison

    To prevent weevils from gaining the upper hand in the garden, chemical agents are superfluous. Affected hobby gardeners can resort to a comprehensive range of effective manual, mechanical and biological means for successful control. The following table provides an overview:

    Manual means mechanical means biological means
    shake off Flower Pot Trap nematodes
    collect Furrow Trap glue rings
    pick buds corrugated trap neem

    The recipe for success for non-toxic control is the combination of several strategies. But be careful: not every combination makes sense. The garden is spared from a weevil plague if adult beetles and larvae are controlled at the same time. The correct procedure of the recommended methods is explained in more detail below.

    Fight weevils manually

    Collecting the beetles is a bit time-consuming but effective

    Weevils have mastered an ingenious deception maneuver as a defense strategy. If the insects sense a threat, they simply play "dead bug". For this purpose, weevils and conspecifics simply drop to the ground. You can use this tactic against the voracious pests. That is how it goes:

    1. spread old cloths or foil under infested plants the day before
    2. get up with the chickens the next day
    3. Shake infested trees and plants

    Even slight shocks cause weevils to drop. For this reason, the collection cloth should be spread out when the beetles are still in their daytime hiding place. Unless you're an early riser, use the night owl variant. After dark, arm yourself with a flashlight and bucket to collect the weevils from the leaves one by one.

    Pick off suspicious buds

    Affected buds should be removed as early as possible

    Egg-laying in flower buds wreaks catastrophic damage in the garden. Often natural means cannot prevent the clever weevil females from laying their eggs. Occupied buds are plucked off in good time so that the eggs do not turn into larvae and adult beetles. Daily checks of the bud development provide information as to whether there is a larva inside. If you stay on the ball, you won't go unnoticed if a bud won't open, is gradually turning brown or is bloating suspiciously.

    Get rid of weevils mechanically

    Weevils can be lured into the trap with simple methods. You don't have to dig deep into your pocket, because you can build effective safety gear yourself. The following models have proven themselves in practice:

    • Fill the flower pot with wood shavings or straw and place it upside down on a stick next to the forage plants
    • Lay grooved decking boards upside down under endangered plants
    • Cut the corrugated cardboard into strips 20 cm wide and wrap them around the tree trunk

    All three traps offer weevils a place to hide during the day. The house-seeking beetles cannot resist overturned pots with tempting fillings. After feeding on the plants, the tired insects crawl in early in the morning and can be collected. The furrows of a worn-out decking board work in a similar way. Apple blossom weevils and hazelnut borers can be caught with strips of corrugated cardboard.

    Use biological means against weevils

    Manual and mechanical weevil control is aimed at controlling the early stages of an infestation. If the beasts appear in the garden again, you should start level 2 of the fight with biological means at the latest now. The focus is on 3 problem solvers who do without toxic components:

    nematodes

    Nematodes are one option to control weevils

    Beneficial versus pests has emerged as a successful model in the near-natural garden. In the fight against vine weevil, the powerful support comes in the form of tiny roundworms called nematodes. The microscopic worms parasitize the pests and thus render them harmless. Because there are only specialized species in the nematode kingdom, different roundworms are used against adult vine weevils than against larvae.

    The nematode genus Heterorhabditis is after the voracious larvae of the vine weevil. Because the fat maggots live in the ground, the watering method has proven to be effective. HM nematodes are dissolved in water and applied with a watering can. The control window is from April to early June. The most important prerequisite for combating success is a minimum temperature of 12° Celsius.In the following 6 weeks, the soil is kept constantly slightly moist, which creates ideal conditions for the hard-working nematodes. A positive side effect: when the nematodes are in action, they also devote themselves to the larvae of the June beetle.

    Steinernema carpocapsae nematodes act as a natural combat force against adult vine weevils. Because nematodes dissolved in water are at a loss against the large beetles, the beneficial insects are set up as a trap. The nematodes rest in the grooves of a wooden board in a life-sustaining gel. Place the trap with the grooves down on the garden floor. If a vine weevil crawls under the board, it catches the nematodes that kill it.

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    glue rings

    Glue rings on tree trunks form a poison-free barrier against cunning weevils. Optionally, a special glue is applied directly to the bark or attached as a glue-coated band around the trunk. Because many weevils do not like to fly or are unable to fly, they crawl up the tree trunk towards the crown to feed or lay eggs there. The pests stick to the glue ring and die. Incidentally, the sticky tapes are excellent for protecting endangered potted plants from beetle infestation. Attach a glue ring to the top edge of the jar.

    neem

    Squeezed seeds of the neem tree spoil the appetite of vine weevils. In specialist shops you can get the remedy as a neempress cake. Just 50 grams per square meter are enough to put an end to the pests. Work the preparation into the surface of the soil, ideally near susceptible plants. The neem oil contained in the press cakes is a deadly poison for weevils. However, neem is safe for humans and pets. It is important to note that a combination of neem and nematodes is counterproductive and does not end well for the roundworms.

    Neem is a great remedy for various pests

    tips

    If hedgehogs live in your garden, harmful weevils have a bad hand. The pricked beneficial insect likes to eat vine weevils and the like. You should also not pursue a mole, because it eats up fat beetle larvae in the garden soil with great pleasure.

    Weevil in the house - what to do?

    Weevils get into the house in a number of ways. They often travel as stowaways in the substrate of new potted plants. Occasionally, vine weevils march from outside into living quarters on their strong legs. Shrubs close to the house or potted plants on the terrace and balcony serve as a starting point. You rarely see the nocturnal secret light doors. Rather, the typical, semi-circular feeding pattern on the leaves of your indoor plants reveals the presence of weevils in the apartment, not infrequently in the kitchen or even in the bathroom. How to get rid of the pests:

    Flower Pot Trap

    With a slight modification, the proven flower pot trick from the garden can be transferred to weevils in the home. Use a plastic pot. Cut a 1 to 2 centimeter small, semi-circular entrance into the edge of the container. Then pad the pot with wood wool, cotton wool or straw. Place the beetle trap near plants that have been eaten. If you don't want to cut the flower pot, place a lego brick or piece of wood under the rim. Vine weevils can't resist the cozy daytime hideout. Empty the pot trap into the organic waste bin every day and repeat the process until there is no more damage to the plants.

    nematodes

    The flower pot trap only defeats adult weevils in the house. Because you can never be sure if oviposition has already occurred in potting soil, we recommend the double strategy with HM nematodes. You can purchase the hard-working roundworms in specialist shops. The beneficial insects are delivered embedded in clay granules that you dissolve in water. Alternatively, pour or spray the enriched water onto the substrate of infested plants. Weevil eggs or larvae in it have nothing to oppose the nematodes and are destroyed.

    frequently asked Questions

    Can weevils fly?

    Most species of weevil have normally developed wings that enable them to fly short distances. The beetles prefer to stay on the ground and move comfortably on their strong legs. Thanks to the hairy soles of their feet, weevils can even master smooth surfaces. A few species rely entirely on their legs because they lack wings. These include the large black weevil (Otiorhynchus coecus), whose habitat extends over the low mountain ranges and the Alps.

    Are my fruits and vegetables still edible if I use nematodes to control the vine weevil?

    Nematodes of the genus Heterorhabditis specialize on beetle larvae. The microscopic roundworms enter a larva through body orifices or the skin. There they secrete bacteria into the larval blood. These bacteria multiply explosively and kill the beetle larvae within a few days. Meanwhile, the nematodes feed on the bacteria and multiply in turn. The nematodes have no interest in the plant in question. There is therefore no need to worry that the beneficial insects could colonize fruits or vegetables.

    Can we identify weevils from the feeding pattern?

    Weevils create an unmistakable feeding pattern on infested plants. Semicircular indentations can be seen on the leaf edges, which are more or less pronounced. Small weevil species leave typical gear-like indentations on the leaf edges. Species that specialize in eating wood give themselves away by gnawed areas on the bark.

    What really helps against weevils?

    Weevils have a hidden, nocturnal lifestyle and have a hard chitinous shell. These properties make the beetles immune to all kinds of contact insecticides. If you suspect an infestation, a nightly check with a flashlight will provide the evidence. You can collect the tracked specimens by hand. A flower pot stuffed with wood shavings, in which the beetles gather during the day, is more effective.

    tips

    As stowaways in potted plants, weevils are brought into the garden and into the house. It cannot be seen from the substrate whether it is infected with eggs or larvae. The best prevention against the voracious brood is timely repotting of each new plant. Ideally, subject the fresh potting soil to disinfection in the oven at 100 degrees Celsius before using it.

Category:

Animals in the garden