"Frost affected the valleys and plains in different ways and hit young hazelnut plants particularly hard. The apexes and distal portions of shoots have been compromised by temperatures reaching -2.5°C, which the literature reports as the minimum threshold trees at this stage of development can withstand. The minimum threshold might have spared inflorescences thanks to the thickness of the vegetable walls," explains Claudio Sonnati, Agrion technician for hazelnut cultivation.
The rain that fell after the frost and the relative increase in humidity actually favour the development of bacterial blight (Xanthomonas campestris pv. corylina).
"All the situations that determine physiological stress due to negative atmospheric events (frost and/or hail) slow down the vegetative activity of hazelnuts, so it's better to wait a few days for photosynthetic activity to recover before intervening," explains Maria Corte, Agrion technician for hazelnut cultivation.
For young 1-3 year-old orchards, we recommend cutting the affected parts and intervening with a copper-based product with wettable sulphur to favour healing. Frozen vegetation cannot absorb any substance as it is necrotised, so using leaf and/or soil fertilisers is useless.
On plants in production, any type of fertilisation (leaf and/or soil) carried out on affected trees during this phase of initial setting stimulates the vegetative phase and might lead to flower abortion.
On plants in production, any type of fertilisation (leaf and/or soil) carried out on affected trees during this phase of initial setting stimulates the vegetative phase and might lead to flower abortion.