P&PDL Picture of the Week for
August 11, 2008

Tubakia Leaf Spot on Oaks

Gail Ruhl, Senior Plant Disease Diagnostician, Department of Botany & Plant Pathology

Tubakia leaf spot (formerly called Actinopelte leaf spot) is a common late-season fungal leaf spot disease on Oak as well as several other tree species. Some years, such as this year, the disease occurs earlier than usual, presumably because of excessive wet weather earlier in the season. Symptoms vary from tree to tree and can include small to large dark brown or reddish-brown spots or blotches on leaves of trees in the red oak group ( such as pin oak and red oak). The symptoms will sometimes mimic severe iron chlorosis symptoms - in fact, both problems are often present on the same tree. Tubakia leaf spot can cause early defoliation of heavily infected oaks, but the disease usually develops late enough in the growing season that no long-term adverse effect on the health of the tree occurs. Proper maintenance of affected trees to reduce root stress (see HO-140) will help to reduce the effects of this disease on overall tree health.

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Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service