The Hazelnut Borer is small but does great damage. If it nests in the garden, you need to act quickly.
If you have hazelnut bushes or trees in your garden, you may have to get to know the hazelnut borer. This pest belongs to the weevil family and is very similar to the squirrel borer. However, he is a bit bigger. You don't even have to spot the beetle itself to recognize an infestation. It is enough if you discover a lot of hazelnuts with a small hole. Then you can be sure that the hazelnut borer has nested somewhere nearby.
The holes are created because the females of the small yellow-brown to brown beetles pierce the nuts with their rather long proboscis and then lay their eggs in the fruit. The larva then feeds on the inside of the nut, causing the nut to fall off.
Hazelnut borer damage
In May and June, the female beetles drill into the unripe, green nuts and lay one egg in each one. The larva eats the nut from the inside and as soon as it falls off, it crawls out through the hole. It then burrows into the ground and pupates there. The pupated larva can then spend up to three years in the ground. Sometime in the spring, the adult beetles finally emerge.
The hazelnut borers don't just attack the hazelnut tree. Before attacking the leaves of hazelnut trees, the beetles first attack the fruits and leaves of other trees, especially fruit trees. However, most gardeners only notice an infestation when the nuts already have round boreholes. If you crack open an infested nut, you will see that the kernel has been eaten out and only the black excrement of the larva is left inside.
Prevent infestation with hazelnut borers
Controlling the hazelnut borer is not easy because there are no approved insecticides for the home garden. These are only available for commercial cultivation. The only thing you can do is try to get a special permit from the plant protection agency. Otherwise you a fewWays to prevent a jibe nut borer:
Tip 1 - place early maturing varieties in the garden:
It is easier to prevent the pest by taking appropriate measures. This begins with the planting of the hazelnut tree or bush. It is ideal if you only place early-ripening varieties in the garden, as these are by no means as susceptible as other varieties.
Tip 2 - Grow a hazelnut tree as a single stem:
In addition, it is best to grow the hazelnut tree as a single-stem standard. Then you have the option of attaching a glue ring to the trunk so that the beetles cannot even get into the crown of the tree. Although female hazel borers can fly, they are lazy and prefer to crawl.
Warning: Although this glue ring promises success, it cannot always keep all animals away.
Tip 3 - Shake off the hazelnut borer regularly:
Another step is regularly shaking off and collecting the bugs. Before you start shaking the plant, you should spread a light-colored cloth or foil underneath it. The pests are still sluggish in the morning, so this is the ideal time of day to do this.
Tip 4 - Check hazelnuts regularly:
In May and June you should check the nuts regularly for holes and remove any that are damaged.
Fighting larvae and beetles properly
You may have heard the advice to dig up the ground in the fall to destroy the larvae that hibernate in it. However, this usually causes great damage to the plant, as it is a flat-rooted plant. That's why you should definitely take other paths.
Tip 1 - apply calcium cyanamide fertilizer:
To combat the larvae of the hazelnut borer, you should apply a calcium cyanamide fertilizer in spring. This also contains some hydrocyanic acid, which can cause the death of the larvae.
Tip 2 - use parasitic nematodes:
You can also try using parasitic nematodes. These can kill the larvae in the soil if you get the timing right.
Tip 3 - Spray Spruzit:
To destroy the beetles climbing up the trunk, you can spray Spruzit (e.g. NEUDORFF Spruzit Schädlingsfrei). This consists of rapeseed oil and is therefore harmless to bees.
Tip 4 - Use chickens as pesticides:
If you have chickens in the garden, larvae and beetles are foundand favorite food for them. If the hazelnut tree or bush is in an area of the garden where the chickens cannot do much damage, you should let them roam around the hazelnut plant for a few days.
Tip 5 - Cut back the hazelnut bush:
If you can do without the nuts for a season, you can cut the shrub back heavily. To do this, simply cut off the fruit buds in spring.