Effect of Nitrogen Concentration in Juvenile Foliage of Rhododendron on Phytophthora Dieback Severity

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Abstract
Nitrogen concentration in juvenile foliage of rhododendron cultivar Roseum Elegans was significantly and positively correlated with size and number of lesions caused by Phytophthora cactorum. Low numbers of tiny lesions were produced on nitrogen-deficient plants with concentrations of 0.7% in juvenile foliage. High numbers of large lesions that killed plants were produced on plants with nitrogen concentrations of 1.8-2.5% in juvenile foliage. Adding nitrogen to low-fertility plants on which small lesions had developed resulted in an increase in lesion size and eventual plant death.
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