Determination of Important Weed Species, Densities and Frequencies in Hazelnut ( Corylus avellana L.) Orchards in Düzce Province

Hazelnut ( Corylus avellana L.) cultivation has strategic value for T & uuml;rkiye, which is a leader in global hazelnut production. This study aims to determine the important weed species, densities, and frequencies in hazelnut orchards in D & uuml;zce province. The presence of weeds is a significant challenge in hazelnut cultivation as they compete with the crop for nutrients, water, and sunlight, while also serving as hosts for pests and pathogens. Effective weed management is critical to maintaining yield and quality. Field research was conducted in 50 hazelnut orchards in 8 districts of D & uuml;zce and weed densities and frequencies were calculated using the Odum & Barrett method. In the survey studies conducted in D & uuml;zce hazelnut orchards, it was determined that 103 weed taxa belonging to 31 families and the ones with the species with the densest populations included Potentilla reptans (creeping cinquefoil) (35.46 plants m-2), Poa pratensis (meadow grass) (12.15 plants m-2), and Bromus hordeaceus subsp. hordeaceus (soft brome) (11.97 plants m-2). The most frequent species were calculated to be Potentilla reptans (creeping cinquefoil) (81.80%), Oenanthe silaifolia (narrow-leaved water-dropwort) (78.34%) and Lapsana communis (nipplewort) (60.72%). Among the families identified, the Poaceae family has the highest number of species (19), followed by Fabaceae (14) and Asteraceae (13). Studies have detected those motorized scythes and herbicides, whose increased use may cause environmental effects and increase pest problems, are widely used in weed control. Identifying weed species and understanding their density and frequency will contribute to the adoption of more precise and environmentally friendly control methods and thus to increasing productivity and sustainability in hazelnut cultivation. Based on these findings, by applying targeted weed control measures, yield losses can be significantly reduced, beneficial organisms can be protected and the overall productivity and economic sustainability of hazelnut agriculture in D & uuml;zce Province can be contributed.