Peggy Sellers, Gail Ruhl, and Paul Pecknold, Purdue University
Hot weather of summer brings with it yellowing and premature drop of tuliptree leaves. This unexplained disorder, apparently caused by environmental stress, commonly develops in tuliptrees during hot dry weather. An additional symptom that frequently accompanies the leaf yellowing is the appearance of circular, black spots between the veins of the yellowing leaves. The black spots are often misdiagnosed as a fungal leaf spot. Though alarming in appearance, this noninfectious problem does not affect tree vigor or health; affected trees will not die or show signs of decline. Fungicide sprays are not required.
The best management for these stressed trees is to thoroughly water during dry periods and fertilize appropriately. The most beneficial method of watering is to apply an amount equal to two inches of rainfall every 2 or 3 weeks. Detailed information about proper fertilization is available in Purdue's Extension publication, HO-140-W Fertilizing Woody Plants (PDF 64K - Requires Adobe Acrobat to view and print).
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| Physiological Leaf Spot of Tuliptree (Photos by Steve Mayer, Marion County CES) |
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Plant and Pest Digital Library Project, Purdue University, West Lafayette, Indiana.