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Karen Rane, Plant Disease Diagnostician
During the spring of 2000, we received several spruce samples with needle discoloration and/or loss of needles. In most cases, we found no evidence of infectious disease or insects.
Similar symptoms can be caused by drought stress. The summer and fall of 1999 were very dry, and trees not receiving supplemental irrigation during dry periods might show symptoms the following spring that might be due to drought stress. When these samples arrive, it is difficult to tell if the trees will recover. If no new growth develops during the following spring and early summer, then the trees will not recover. If new growth develops on the branches, owners need to make sure the trees are watered during dry weather.
Dr. Paul Pecknold recommends thoroughly watering stressed trees around the tree's drip line with a slow, deep soaking of the soil (12-18 inches) once or twice a month.
Plant and Pest Digital Library and Digitally Assisted Diagnosis, Purdue University, West Lafayette, Indiana.