The hazelnut is a species that, due to its rusticity and adaptability, is found spontaneously in various hilly and low-mountain environments, but is also cultivated for income or in the private sector and lends itself to the organic agricultural method.
As flexible as it is in accepting different soil conditions, the hazelnut plant can suffer in too asphyxiated soils and can sometimes be attacked by some animal parasites.
Let's see which are the main insects and parasites that threaten the hazel, even if serious damage is rare because it is not a particularly delicate species.
Eriofide of the core
It is a mite which affects in particular the hazelnut buds, chosen as their wintering sites. The presence of this small insect can be recognized by the size of the buds. The buds attacked by the eriophid in fact take on an anomalous appearance, swelling rapidly and becoming reddish in color, eventually falling prematurely without being able to give life to branches. Since this is a mite, sulfur-based treatments are effective, after carefully reading the instructions on the product packaging.
Adults of this insect appear around the mid-May, laying their white-orange eggs on the bark of the trunk or the branches of the hazel. The larvae that emerge from the eggs dig tunnels in the wood, damaging the internal vessels and consequently causing yellowing of the crown and early fall of the leaves. The branches affected by the agrilo show a characteristic spiral swelling. The severely affected plant hardly recovers and is more likely to die, which is why it is very important to identify the first symptoms and prune all the affected parts by eliminating them from the orchard or hazelnut and thus freeing themselves from the presence of the agrilo.
The adult of balanino it is a brown insect, it has a long rostrum, that is a sort of beak thanks to which the female can pierce the shell of the maturing hazelnuts, and therefore still tender, to lay the eggs. A larva is born from the egg that begins to live at the expense of the seed, and from which it comes out only when ripe to fall to the ground for wintering. Natural treatments based on the entomopathogenic fungus Beauveria bassiana done in autumn can help contain the attacks of this insect while remaining within the scope of biological methods.
The hazel can be affected by various types of bedbugs: the green bug, the brown bug and for some years also the dreaded Asian bug. The damage that bedbugs can cause are of various types: if prick the fruit in the early stages of its formation, they block its development and the hazelnut falls to the ground early. If, on the other hand, they prick it later, when the seed has already partially formed, they cause the so-called "cimiciato", ie browning of the pulp, whitish spots and above all a serious deterioration in quality and deterioration of the flavor of the hazelnuts, which makes them unusable.
Bedbugs are treated in organic farming with natural pyrethrum, with Azadirachtin or with mineral oils.
Popolia japonica is a metallic-bronze green colettero originally from Japan, found in Italy for the first time in 2014 in the Ticino park. It is an extremely polyphagous species, it is found between June and September and among the cultivated and spontaneous plant species it attacks, devouring the leaves up to the ribs, there is also the core. The problem is that it has no natural predators in our areas, it has spread particularly in Piedmont and Lombardy, where traps and treatments with entomoparasitic nematodes have been tested, with research that is still going on. In organic farming they can also be used pyrethrum and kaolin, the latter a very fine white clayey mineral that creates a patina on the leaves with a phagodeterrent effect (that is, it inhibits feeding) towards the adult of the Popilia.
The rodilegno are lepidoptera that at the stage of larva they dig tunnels in the branches and in the branches, and we can recognize their presence by noticing wood rosure and excrements outside the penetration holes. To limit its presence it is useful to place artificial nests to favor woodpeckers, birds that feed on these larvae. Direct ecological treatments are performed with products based on Bacillus thuringiensis kurstaki.
They are small insects with a rigid shield that attach themselves to the branches by stinging them and sucking their sap. If the cochineal infestation concerns a few plants, it is possible to brush the branches with metal tools, otherwise you can do spraying with fern macerates or treatments with mineral oils, which are allowed in organic farming even if they are petroleum derivatives.
Ifantria or American caterpillar
It is a defoliator moth that resembles the pine processionary moth, but which is harmless to humans and animals and which, although polyphagous, does not attack conifers. The ifantria is widespread above all in northern Italy and here usually quite cold winters manage to contain its presence by killing many wintering forms, but the milder temperatures that have been recorded in recent years probably have not helped as limiting factors. The damage American caterpillar larvae do is there skeletonization of the leaves, of which they save only the ribs, leaving all the canvas and excrement on them. The ifantria also affects the hazel but its favorite species seem to be the mulberry and the American maple, therefore consider spy plants for this parasite. To control it, it is necessary to eliminate and destroy the affected branches full of larvae and treat with Bacillus thuringiensis kurstaki, preferably in the evening and promptly because this ecological product is more effective on young larvae.
Hares and mini hares
Young plants recently planted in certain areas risk being grazed by hares or mini hares, attracted by young shoots. Sufficient protection is represented by network rings provisionally placed around all young hazelnut specimens.