Nitrogen status affects growth, chlorophyll content and infection by Fusicladium oleagineum in olive

Olive leaf spot, caused by Fusicladium oleagineum, is the most common foliar disease in olive (Olea europaea L.). The influence of nitrogen fertilization on olive spot development was evaluated on the susceptible cultivar 'Picual' in hydroponic culture, potted plants and mature olive trees. Two levels of nitrogen, using different solutions of Ca(NO3)2, KNO3, NaNO3 and urea, were applied. Shoot growth, and leaf chlorophyll and nitrogen concentration were assessed. Plants or detached leaves were artificially inoculated with a conidial suspension of the pathogen. A significant increase in shoot growth, chlorophyll and nitrogen concentration in leaves and disease incidence was observed in plants subjected to a high nitrogen treatment. However, plants with low nitrogen level reached a reduction of 59%, 55%, 42% and 65% in these parameters, respectively. This study shows that nitrogen fertilization management may aid in reducing olive leaf spot development.