Above all, the larvae of the scarab beetle, known as grubs, are a major problem in agriculture and in the garden in some years, as they often destroy large-scale plantings within a short time due to their frequent appearance in large numbers. We have summarized for you in this article what actually helps against the different species.

The rhinoceros beetle is just one of the 27,000 species of scarab beetles that look very different

Table of Contents

Show all
  1. the essentials in brief
  2. damage picture
  3. prevention
  4. Fight
  5. What are scarab beetles?
  6. Look
  7. way of life
  8. frequently asked Questions
  9. What to do if scarab beetles get lost in the apartment?
  10. How long do scarab beetles live?
  11. Can scarab beetles bite?

    12. the essentials in brief

    • There are about 27,000 scarab beetle species worldwide
    • Scarab beetle grubs nibble at the roots of plants while adult beetles feast on the leaves
    • Scarab beetles are best controlled by nematodes or with the help of predators
    • It is even better to prevent infestation by regularly hoeing, root protection mats or insect nets

    This is how you recognize a scarab beetle in good time

    By no means do grubs eat up plant roots for years, but initially feed on humus. Only from the second year do the larvae feast on the fine roots (and depending on the species also on other plant residues), before digging up to 60 centimeters deep into the ground and pupating. They remain in this state for another one to two years. While the adult beetles can be spotted quite quickly - and egg-laying is likely - the grubs are often only discovered by chance.

    The plants on the infested areas die apparently without cause. If you can rule out other reasons, the grub infestation can be substantiated quite well by a test dig in the affected area: the yellowish-white larvae are in the excavation. By the way, you don't have to dig very deep, because the little animals are only a few centimeters below the surface of the earth.

    While the beetles “only” cause damage above ground, the larvae secretly eat the roots

    Prevention is better than fight

    You can prevent an infestation with scarab beetles and their larvae with a few targeted measures. However, these methods are not 100% secure. The most important thing is not to leave the lights on in the garden during the main flight time of the various species: the mostly nocturnal or twilight-active animals are attracted to it and prefer to lay their eggs near the light sources. Other useful preventative options include:

    • insect protection nets: mainly on compost and manure heaps and in open ground
    • root protection mesh: protect the rhizomes of plants from the larvae
    • lawn curbs: Beds surrounded by deep curbs, the grubs cannot get through here
    • groundwork: hoeing, raking, pulling weeds and regularly digging up the soil in spring or autumn disturbs and damages the grubs

    tips

    To prevent lawns from dying off caused by grubs, you should scarify the turf regularly. However, if that doesn't help anymore, you should remove the dead lawn, dig up the area deeply and sow it again.

    Combat scarab beetles effectively

    “Collect the cockchafers and rip off their legs and wings. Then roast them in hot butter until crispy. Then cook them in chicken soup.” (Century-old recipe for cockchafer soup)

    If the damage is already visible, the plants eaten by grubs cannot be helped. Since the larvae devour the underground roots, the above-ground parts of the plant can no longer be supplied with nutrients and dry up. In addition, May beetle larvae appear in large numbers - where you find a maggot, there are certainly many others in the ground. So it's no wonder that the earlier numerous populations were collected and, for example, processed into a nutritious cockchafer soup - maybe your grandparents still know it.

    With regard to effective control, you have the following options in the garden.

    collect

    Even in earlier times, one of the main activities of children during the summer months was collecting May beetles and their larvae. Even today, the method for the hobby garden is effective, even if it is tedious and time-consuming. The easiest way to collect the grubs is after a heavy downpour, because then the animals come to the surface and can be easily picked up. Such rain can be imitated artificially by watering the infested areas vigorously.

    Alternatively, simply dig up the soil infested with grubs and thus bring the larvae to light. This method also has the advantage that the soil is loosened and weeds are removed.

    Control biologically with nematodes

    Nematodes specifically against the larvae of May beetles or June beetles are commercially available, which reliably put an end to the pests. These are microscopic roundworms that come in clay granules. Simply mix the granules with the irrigation water and water the affected areas in the garden extensively. The nematodes become active in the soil, penetrate the grubs and kill them.

    Natural enemies

    Birds are the best defense against scarab beetle infestations

    One of the best ways to get rid of pesky grubs is to make your garden welcoming to hedgehogs, moles, bats, and birds. The fat maggots as well as the adult beetles like to eat them and thus keep the population low in a completely natural way. Mice, martens and large ground beetles also like to eat grubs. To make the beneficial insects feel comfortable, install

    • appropriate quarters (birdhouses, bat boxes, piles of brushwood)
    • Drinking troughs and feeders with a few treats (feed birds in winter!)
    • Planting of fodder and protective plants, such as dense hedges

    If you are also the happy owner of a flock of chickens, you can let them run over fallow beds in spring and autumn and over meadows and lawns all year round. The animals selectively peck the grubs out of the ground.

    Insecticides against scarab beetles?

    Some pesticides that reliably eliminate the grubs are approved for home gardens, hobby gardens and lawns. These include, for example, products made from the seeds of the neem tree native to India, whose toxic ingredients hinder the larvae in their development. However, if possible, you should not use insecticides, as these - regardless of whether they are chemical or natural agents such as neem oil - always have serious effects on the entire ecosystem in the garden and thus also on useful animals.

    Just because a drug is labeled "natural" doesn't mean it's safe. After all, nature itself produces the most harmful toxins and is therefore anything but "gentle".

    What are scarab beetles?

    The scarab beetles (lat. Scarabaeidae) are a very large and complex family within the order of beetles (lat. Coleoptera). About 27,000 different species in about 1,600 genera belong to the worldwide beetle family, which looks very different from the outside and can be between a tiny two millimeters and a strikingly large 16 centimeters long. Not all species pose a problem in the hobby garden, some - such as the rhinoceros beetle, which is threatened with extinction and is therefore a nature reserve - are also considered to be downright beneficial.

    species

    Typical species of scarab beetle relevant for the garden are the following:

    • June beetle: also ribbed curlew beetle, lat. Amphimallon solstitiale
    • Common cockchafer: also field cockchafer, lat. Melolontha melolontha
    • Shiny gold rose chafer: also common rose chafer, lat. Cetonia aurata
    • rhino beetle: Latin Oryctes nasicornis, feeds on dead wood and is therefore often found in bark mulch
    • garden beetle: Latin Phyllopertha horticola, are often confused with the June beetle, but cause little damage

    For many centuries, the may beetle in particular was notorious as a pest and was able to cause considerable damage - and thus also famine - every year due to the immense feeding activity of its grubs. Nowadays, the may beetle has become rather rare due to drastic measures mainly in the 1950s and 1960s, but it still causes great damage in warm years and in certain regions. The following video shows the newly reappeared problem quite impressively:

    youtube

    Typical appearance of the scarab beetle

    The scarab beetles mentioned above look very similar, so confusion cannot be ruled out. However, an exact determination of the species occurring in the garden is important, because otherwise the control measures can come to nothing - not every beetle grub reacts as desired to the initiated elimination methods. For this reason you will find some relevant clues for precise species identification in the following table:

    cockchafer June beetle Gold shiny rose chafer garden beetle rhino beetle
    Happen almost all of Europe, rare in the Mediterranean Northern and Central Europe outside the mountains Europe and Asia, B. a. Central and Northern Europe all of Europe and Asia Europe, Asia, Africa
    habitat open landscapes with few trees Fields, gardens, forest edges, parks Hedges, gardens, forest edges, parks on meadows, fields, at the edges of forests, in gardens and hedges especially in forests, also in tree-lined gardens and parks, compost heaps
    frequency now more often again locally dependent, common to rare locally dependent, common to rare widespread Rare
    Diet of the adult beetle leaves of deciduous trees leaves and flowers often in flowers (pollen, nectar, plant sap) Birch, hazel and oak leaves, rose and cherry blossoms Plant juices (e.g. from tree leaves)
    feeding of the grubs Plant roots, plant remains Deadwood, often found in bark mulch and compost Plant roots, especially in the lawn Deadwood, often found in bark mulch and compost
    elytra red-brown, can be lighter or darker three raised longitudinal ribs, dotted between two broad longitudinal ribs, white transverse grooves and spots light brown, six dotted longitudinal stripes on each wing smooth and shiny, with fine rows of dots
    coloring except for legs, elytra and antennae black dark yellow to brown green to bronze-colored, shiny metallic, reddish-gold underside except for the elytra black-green, shiny metallic dark reddish brown to black, very shiny
    size two to three centimeters 14 to 18 millimeters 14 to 20 millimeters 8 to 11 millimeters 2.5 to 4 centimeters
    Special marks End of abdomen not covered by wings bright median line between pronotum and elytra different colors possible, but always shiny metallic dense hair all over the body the eponymous "horn" is only worn by the males
    flight time from early May to early June from the beginning of June April to October late May to late June May to June
    larval activity from July from mid to late July from June July to October from June
    grub appearance three pairs of legs, yellowish white, brown head capsule, curved yellowish white, brown head capsule, curved whitish, rather plump, hunched posture yellowish white white, cylindrical, hunched posture
    grub size apparently ten segments up to five centimetres up to five centimetres comparable to the cockchafer larger than typical grubs, up to 12 centimeters
    classification pest pest beneficial pest protected beneficial

    way of life and reproduction

    Scarab beetles show very different lifestyles and nutritional preferences. In addition to the grubs that live on plant roots, there are species that primarily live on dead wood or collect dung. The last-named group includes, for example, the various dung beetles or the species known as “pillworms”. Some Scarabaeidae are extremely useful in the garden - such as the rose chafer or rhinoceros beetle - others cause considerable damage. Many scarab beetles are nocturnal or only wake up at dusk.

    development of the larvae

    The life cycles and the development of the larvae also differ greatly between the individual species. The following table shows the main differences between the garden pests cockchafer and June beetle:

    cockchafer June beetle
    egg laying May to June June to July
    larval hatch end of June end of July
    pupation July August August September
    duration of the larval stage 3 to 5 years 2 to 3 years
    hatching of adult beetles April to May May to June

    Larva, pupa and beetle - All beetles go through these steps

    Also characteristic of many scarab beetle species is the fact that the larvae sometimes remain in the ground for years. The grubs only pupate after two to five years, only to hatch as adult beetles in the spring. However, the adult animals called imago do not live very long: May beetles and June beetles usually do not get older than four to six weeks and usually only lay eggs once. For this reason, an infestation often only occurs every several years - May beetles, for example, plague the gardener about every four years.

    background

    May beetle or June beetle?

    The larvae of the various scarab beetles look confusingly similar to one another. However, you can tell them apart by the time they appeared, where they were found, and how they moved. Turned on their backs, the grubs of the following varieties crawl away as described:
    • cockchafer: lateral, meandering
    • June beetle: crawling on its stomach
    • rose chafer: on the back, caterpillar-like

    The larvae of the rhinoceros beetle, on the other hand, are easily recognizable by their size.

    frequently asked Questions

    What to do if scarab beetles get lost in the apartment?

    If a May or June beetle strays into your home, simply catch it and release it back outside through a window. The animals will most likely mistake you or your furniture for a tree and quickly land on it. Scarab beetles are neither dangerous nor poisonous to humans.

    How long do scarab beetles live?

    While the beetle larvae - depending on the species - remain in the ground for up to four years, adult scarab beetles are usually not granted a long life. May beetles and June beetles, for example, fly for four to six weeks at the most, only to die immediately after laying their eggs.

    Can scarab beetles bite?

    If you have a May or June beetle on your arm and are annoying it, it can bite painfully. However, this happens only very rarely and is completely harmless.

    tips

    Plant garlic as well as delphiniums and geraniums (i.e. the pelargoniums more commonly known as balcony flowers) between your beds and thus prevent an infestation of grubs. The animals do not like these plants and try to avoid them.

Category:

Animals in the garden