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Nicolas Tremblay, Tarif Charbaji, Francois Fournier, and Odile Carisse

Scientific literature contains several examples of disease development influenced by fertilization practices. A set of data collected by the «Scouting and Research Network, South of Montreal Area» and consisting of disease and tissue analysis data on carrot and onion crops was made available for principal component analysis. It was hypothesized from the analysis that high N tissue levels would reduce Cercospora carotae and Botrytis squamosa importance on carrot and onion leaves, respectively. In a controlled environment study, Cercospora spots were inversely related to urea levels sprayed on carrot leaves although urea had no influence on plant growth. In a field study with onion, however, urea sprayed at 10 kg/ha, alone or in combination with a fungicide, had no effect either on Botrytis or on maturation or yield. With these mixed results, more research seems needed to assess the potential of nutrient sprays in reducing pesticide use.