Small holes in the shell of hazelnuts ring alarm bells. The hazelnut borer was at work. Here you can find out what the term means, how to identify the pest and combat it biologically.

Female hazel borers bore holes in the unripe hazelnuts and lay their eggs there

Table of Contents

Show all
  1. the essentials in brief
  2. What is a hazelnut borer?
  3. Fight hazelnut borers
  4. Combat hazelnut borers manually
  5. Control hazelnut borers biologically
  6. Enemies destroy hazelnut borers
  7. frequently asked Questions

    8. the essentials in brief

    • Hazelnut borer is a 6-9mm black, brown and white weevil whose reproduction and feeding is dangerous for hazelnuts as well as the buds, blossoms and fruits of other fruit trees.
    • Females drill a hole in the shell to lay eggs. Development of egg and larva takes place inside a hazelnut from June.
    • Effective biological control agents include: shedding, crop selection, glue rings, nematodes, and pecking chickens and ducks.

    What is a hazelnut borer?

    A hazel borer is a beetle with a very long proboscis

    Hazelnut borer is a beetle from the large family of weevils. Mating females lay their eggs in unripe hazelnuts so that voracious maggots can develop undisturbed in the protection of the shell. After a month, an adult larva leaves the empty shelter, leaving a prominent hole in the shell. The combination of ruthless propagation and destructive nutrition has earned the hazelnut borer its reputation as a pest. The following profile provides compact information on the beetle and larva:

    Characteristics hazelnut borer larva
    size 6-8.5mm 12-15mm
    color scaled black-white-brown yellowish white
    body shape oblong-oval wormy
    Special feature long, dark brown proboscis brown head
    nutrition fruits, leaves, hazel hazelnut
    botanical name Curculio nucum
    family weevil

    The following sections provide more detailed information on the profile with more detailed explanations on appearance and lifestyle.

    Identify hazelnut borers

    Hazelnut borers have a black body, which of course remains hidden from the viewer. A patchy pattern of brown, yellowish, and white scales covers the body. A bristly hair crest is characteristic, which extends over the elytra suture. The square, whitish scaly shield has a bare edge on the side. Red-brown antennae and legs complete the appearance. The hazelnut borer clearly sports a snout that is as long as the female and significantly shorter in the male.

    The larvae, which are up to 1.5 centimeters long, have the typical cream-white maggot look. A strong mouthpart with sharp teeth sits on the brown head capsule. With that, the little worms bite through the tough nut shell on their way to freedom.

    Destructive way of life of beetle and larva

    The larvae of the hazelnut borer feed on unripe hazelnuts

    The following foray into a hazelnut borer year reveals why the beetles are assigned to the pests:

    • start of activity: from March/April, adult beetles migrate from their winter quarters in the ground
    • nutrition: Maturation feeding on buds, flowers and leaves of cherry, pear, apple, peach and other fruit trees
    • propagation: from June mated females approach ripening hazelnuts with a soft shell and a diameter of 8-12 mm
    • egg tray: Female bores hole in shell to place an egg
    • egg hatch: within a week
    • nutrition: Larva feeds on the flesh under the peel for three to four weeks

    The adult larva enlarges the already existing hole in the shell and squeezes through. As a rule, the affected hazelnut has already fallen from the tree. This means that the maggot can easily leave its nursery and digs 10 centimeters deep into the ground, where it pupates and overwinters.

    digression

    Trump card early hazel varieties

    Early maturing varieties are the ace up the sleeve of natural hobby gardeners in the fight against hazelnut borers. In fact, early hazelnut varieties (Corylus avellana) with hard, heavily woody shells are well armed against female beetles with eggs in their luggage. Hazelnut borer ladies bit their teeth off on premium varieties such as 'Nottinghams Earliest', 'Bergers Zellernuss' and 'Lange Zellernuss', so that egg-laying is doomed to fail. A positive side effect: Early varieties already shine with their distinctive catkins in February, which the first bees, bumblebees and butterflies really appreciate.

    Combating hazel borers - an overview of biological agents

    Once the hazel borer larvae have taken up residence under the hard nut shell, the beasts are difficult to get at. Effective control must start where mated females are on their way to lay eggs or where cunning maggots and beetles lurk deep in the ground. The following table provides an overview of effective non-toxic pesticides:

    Manual means Biological means beneficials
    Shake off glue rings Chicken
    select harvest nematodes ducks

    The competent application of the recommended control methods is explained in the following instructions in a practical and comprehensible manner.

    Combat hazelnut borers manually

    Manual control methods remain on the heels of hazel borers throughout the season. This procedure does not cost any money, but in return it takes your time and special attention. How to do it right:

    Shake off

    • Spread foil under fruit trees (hazel, cherry, apple, peach, pear and others)
    • From March/April shake the beetle out of the crown (ideally daily)
    • Destroy and dispose of fallen hazelnut borers

    The more consistently and regularly you shake affected trees, the higher the success rate. In the early hours of the morning, most pests tumble to the ground because the insects are still stiff from the cold.

    Select hazelnuts

    Infested hazelnuts should be collected and disposed of daily

    The first half-ripe hazelnuts fall to the ground early in the summer. If you collect the infested fruits daily, there is a good chance that they will catch the larvae inside. Please dispose of the yield in the household waste and not on the compost. Follow this pattern until harvest time. In particular, nuts with a telltale drill hole in the shell are not suitable for consumption and are sorted out.

    tips

    With a near-natural garden, hazelnut gardeners apply to attract natural enemies of the hazelnut borer. If no pesticides turn the ground into a toxic minefield, piles of leaves and dead wood remain, and wild fruit hedges invite you to linger, the hedgehog feels very welcome. If the cute prickly bear finds a cozy hedgehog house, he likes to settle down and diligently hunts for hazelnut borers and voracious larvae as well as many other pests.

    Control hazelnut borers biologically

    The recommended biological control agents in the table above grab hazelnut borers twice in their pliers. Glue rings target approaching beetle ladies. Nematodes parasitize buried larvae in winter quarters. How to combat hazelnut borers in harmony with nature:

    glue rings

    Glue rings are a non-toxic pesticide on tree trunks. A tape coated with glue is wrapped around the trunk. If hazelnut borers crawl on the bark towards the crown, they stick to the glue ring and die. Equip not only hazelnut trees with the sticky bulwark against pests, but all fruit trees. This is how glue rings achieve the best control success against winter moths, codling moths and other rabble.

    To learn how to properly attach a glue ring, see the following video:

    youtube

    nematodes

    Nematodes are microscopic roundworms that lay their eggs in larvae. This process does not end well for the larva. Primarily the nematodes of the genus Heterorhabditis bacteriophoba (HM nematodes) decimate the hazel borer population in your garden by up to 50 percent. You can purchase the beneficial insects in specialist shops. The tiny roundworms are delivered in clay granules, which you dissolve in water and spread out with a watering can. The best time to fight is from August, when the fat maggots crawl into the ground to hibernate there.

    Feathered enemies crush Hazelnut Borers

    Chickens like to eat hazelnut borers and other pests

    Hobby gardeners who keep chickens have a clear advantage in the sustainable control of hazelnut borers. Pecking chickens are the declared enemies of beetles and larvae. If you set up a temporary outdoor enclosure around hazelnut trees from March to May, no pest will escape the busy chicken beaks.

    The feathered enemies of greedy hazelnut borers and larvae include runner ducks. The cute, flightless ducks are mostly hired to fight snails in the garden. Beetles of all kinds and their larvae are also on the menu of penguin ducks.

    frequently asked Questions

    What kind of damage does a hazelnut borer cause?

    In June, females bore a tiny hole in the still soft shell of young hazelnuts and lay a single egg. After four to five weeks of development inside the nut, a larva eats its way through the shell. The original, barely recognizable, round opening is enlarged to a diameter of up to 2 millimeters. This drilling and drilling hole is an unmistakable sign of damage to an infested hazelnut.

    Can hazel borers fly?

    Yes, adult hazel borers can fly. Like most weevils, hazelnut borers are also equipped with a functioning flight apparatus. However, the beetles prefer to walk around in search of hazelnut trees and other fruit trees.

    What means can be used to prevent hazelnut borer infestation?

    Regular soil tillage in the area of the tree crown from early spring destroys hibernating larvae before they fly out as mature beetles. Thoroughly rake through the soil of the root disk. Ideally, you should then cover the tree pit with a weed or garden fleece that catches beetles that have hatched. Before that, we recommend fertilizing with calcium cyanamide, which has proven itself in the biological control of all types of larvae.

    Where to buy nematodes against hazelnut borers?

    There are numerous shopping sources in specialist shops and on the Internet, such as hardware stores or garden centers. Not all of them take into account the fact that they are living beneficial insects. We therefore recommend buying nematodes directly from competent breeding farms. Here, animal-friendly delivery of the valuable freight is guaranteed.

    tips

    Deep in the ground, hazelnut borer larvae cannot feel safe when Mr. Mole is around. What chicken beaks and nematodes don't catch is just right for the underground beneficial. Fatty larvae do not remain hidden from the sensitive mole nose for long in the winter quarters. For this reason, natural gardeners do not pursue the helpful insectivore and generously tolerate the occasional molehill in the bed.

Category:

Vegetable garden