Hackberry Island Chlorosis

June 14, 2007

Island chlorosis is a disease that appears on hackberry leaves as blocky, yellow spots. The lesions are delineated by veins, giving them the angular look. Early in the disease progression, the yellow spots are surrounded by green, healthy tissue, like yellow islands in a green sea. Whether for this reason or some other, the disease is aptly named island chlorosis. This image by Bruce Paulsrud shows the symptoms.

This disease may be more appropriately called a disorder. In researching the problem sporadically over the years, I have come across writings that say it is thought to be caused by a virus or to be a physiological abnormality. I have not found anything that qualifies as a replicated research paper (but I have not spent much time at this search), so I can't say either with certainty. As far as we have been able to determine, the disorder is a curiosity but does not cause any damage. In any event, the symptoms occur on hackberry, are certainly less of an eyesore than witches'-brooms found on hackberry, and can become intense enough to give the entire tree a yellowed appearance. For those who know of some scientific writings in this regard, please send references to me at npataky@uiuc.edu.

Author: Nancy Pataky