the essentials in brief
- Hazelnut wrench is a 6-9 mm large, black-brown-white weevil whose reproduction and nutrition is dangerous for hazelnuts as well as the buds, flowers and fruits of other fruit trees.
- Females drill a hole in the shell to lay eggs. The egg and larva develop inside a hazelnut from June onwards.
- Effective biological control agents are: shake off, harvest selection, glue rings, nematodes as well as pecking chickens and Ducks.
What is a hazelnut borer?
A hazelnut borer is a beetle with a very long proboscis
Hazelnut borer is a beetle in the large family of Weevil. Mated females lay their eggs in immature hazelnuts so that voracious maggots can develop undisturbed under the protection of the shell. After a month, a full-grown larva leaves the empty-fed shelter, creating a prominent hole in the shell. The combination of reckless reproduction and destructive nutrition has given the hazelnut borer its reputation as a pest. The following profile provides compact information on beetles and larvae:
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| Characteristics | Hazelnut wrench | larva |
|---|---|---|
| size | 6-8.5 mm | 12-15 mm |
| colour | black-white-brown scaled | yellowish-white |
| body shape | oblong-oval | worm-like |
| Special feature | long, dark brown trunk | brown head |
| nourishment | Fruits, leaves, hazel | hazelnut |
| Botanical name | Curculio nucum | |
| family | Weevil |
The following sections provide more detailed information on the profile with more detailed explanations of appearance and lifestyle.
Recognize hazelnut burs
Hazelnut burs have a black body, which of course remains hidden from the viewer. A speckled pattern of brown, yellowish and white scales covers the body. It is characterized by a bristly hair comb that extends over the suture of the wing cover. The square, whitish-scaled label has a bare edge on the side. Red-brown antennae and legs complete the appearance. The hazelnut borer clearly shows a trunk that is body-length in females and significantly shorter in males.
The larva, which is up to 1.5 centimeters long, has the typical creamy white maggot look. A powerful mouth tool with sharp teeth sits on the brown head capsule. With it, the worms bite their way through the hard nutshell on their way to freedom.
Destructive way of life of beetles and larvae
The larvae of the hazelnut borer feed on unripe hazelnuts
The following foray through a hazelnut borer year reveals why the beetles are assigned to the pests:
- Start of activity: from March / April adult beetles leave their winter quarters in the ground
- nourishment: Ripening damage to the buds, flowers and leaves of cherries, pears, apples, peaches and other fruit trees
- Multiplication: from June approach of mated females to ripening hazelnuts with soft shell and 8-12 mm diameter
- Egg tray: Female drills a hole in the shell to place an egg
- Egg hatching: within a week
- nourishment: Larva eats under the skin on the pulp for three to four weeks
The adult larva enlarges the already existing hole in the shell and squeezes through it. As a rule, the infected hazelnut has already fallen from the tree. Thus, the maggot can leave its nursery without any problems, digs itself 10 centimeters deep into the ground, where it pupates and hibernates.
Digression
Trump card early hazel varieties
Fighting the hazelnut borer - an overview of biological agents.
Once the hazelnut borer larvae have moved under the hard nut shell, the beasts are difficult to get at. Effective control must begin where mated females make their way to lay their eggs or where cunning maggots and beetles lurk deep in the ground. The following table gives an overview of effective pesticides without poison:
| Manual means | Biological means | Beneficial insects |
|---|---|---|
| Shake off | Glue rings | Chicken |
| Select harvest | Nematodes | Ducks |
The professional application of the recommended control methods is explained in a practical and comprehensible manner in the following instructions.
Fight the hazelnut borer manually.
Manual control methods stay on the heels of hazelnut worms 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 the foil under the fruit trees (hazel, cherry, apple, peach, pear and others)
- Shake the beetle out of the crown from March / April (ideally daily)
- Destroy and dispose of fallen hazelnut burs
The more consistently and regularly you shake affected trees, the higher the success rate. In the early morning hours, most of the pests tumble to the ground because the insects are still rigid from the cold.
Select the hazelnuts
Infested hazelnuts should be collected and disposed of on a daily basis
The first hazelnuts fall half-ripe and hollowed out to the ground early in summer. If you collect the infected fruit every day, there is a good chance that you will catch the larvae inside. Please dispose of the harvest in the household waste and not on the compost. Follow this pattern until harvest time. In particular, nuts with a telltale hole in the shell are unsuitable for consumption and will be discarded.
Tips
With a near-natural garden, hazelnut gardeners apply to visit natural enemies of the hazelnut borer. If no pesticides turn the soil into a poisonous minefield, piles of leaves and dead wood remain, wild fruit hedges invite you to linger, that feels like Hedgehog welcome. Thinks the cute one Spiked bearer a cozy hedgehog house in front of him, he likes to settle down and diligently hunt hazelnut bores and voracious larvae as well as many other pests.
Fight hazelnut burs biologically.
The recommended biological control agents in the table above grip hazelnut burs twice. Glue rings are aimed at beetle ladies on the march. Nematodes parasitize buried larvae in their winter quarters. How to fight hazelnut burs in harmony with nature:
Glue rings
Glue rings are a non-toxic control agent on tree trunks. A tape coated with glue is placed around the trunk. If hazelnut burs crawl on the bark towards the crown, they stick to the glue ring and perish. Equip not only hazelnut trees with the sticky bulwark against pests, but all fruit trees. This is how glue rings achieve the best results in combating Frost wrench, Codling moth and other rabble.
You can find out how to properly attach a glue ring in the following video:
Youtube
Nematodes
Nematodes are microscopic roundworms that lay their eggs in larvae. This process does not turn out well for the larva. Primarily the nematodes of the genus Heterorhabditis bacteriophoba (HM nematodes) decimate the hazelnut borer population in your garden by up to 50 percent. You can purchase the beneficial insects in specialist shops. The tiny nematodes are delivered in Clay granules, which you dissolve in water and spread with a watering can. The best time to control it is from August, when the fat maggots crawl into the ground to hibernate there.
Feathered enemies destroy hazelnut burs.
Chickens prefer to eat hazelnut worms and other pests
Hobby gardeners who keep chickens have a clear advantage in the sustainable control of hazelnut borer. 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 pests will escape the busy chicken beaks.
The feathered enemies of eaten hazelnut burs and larvae include 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 damage does a hazelnut borer cause?
In June, females drill 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 borehole and borehole is an unmistakable damage to an infected hazelnut.
Can hazelnut burs fly?
Yes, adult hazelnut burs can fly. Like most weevils, hazelnut burs are also equipped with a functioning flight apparatus. However, the beetles prefer to walk around looking for hazelnut trees and other fruit trees.
What means can be used to prevent hazelnut borer infestation?
Regular tillage in the area of Treetop from early spring onwards, overwintering larvae are destroyed before they fly out as finished beetles. Vigorously rake the soil through the root disc. Ideally, cover that Tree grate then with a weed or Garden fleecethat catches hatched beetles. Before doing this, we recommend fertilizing with calcium cyanamide, which has proven itself in the biological control of larvae of all kinds.
Where can you buy nematodes against hazelnut burs?
There are numerous sources of purchase 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 an animal-friendly delivery of the valuable cargo is guaranteed.
Tips
Deep in the ground, hazelnut borer larvae cannot feel safe when Mr Mole is there. What chicken beaks and nematodes do not catch, is just what the underground beneficial organisms are looking for. The sensitive mole-nose does not hide fat larvae for long in their winter quarters. For this reason, natural gardeners do not stalk the helpful insect eater and magnanimously tolerate one or the other molehill in the bed.
