Application of Nitrogen Fertilizer to Control Anthracnose of Black Walnut. Dan Neely, Plant Pathologist, Illinois Natural History Survey, and Professor of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 65:580-581. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-580.

Nitrogen fertilizers enhanced the resistance of Juglans nigra to walnut anthracnose incited by Gnomonia leptostyla and delayed premature defoliation. Application rates were directly correlated with foliar color and tree growth and inversely correlated with disease severity. Ammonium sulfate, ammonium nitrate, and urea were equally efficient sources of nitrogen. Both April and June applications of nitrogen were effective. The addition of phosphorus and potassium often diminished the effectiveness of nitrogen.