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Tree and Shrub Diseases: Leaf Spot

leaf spotLeaf spot is damage to the tissue of tree or shrub leaves, caused by fungus, bacteria, air pollution, insects or weather. The damaged leaf will begin to exhibit spots, ranging in size from a pin-head to the entire leaf and in color from tan, brown, black or red (usually with a border). The tree or shrub may have partial to full defoliation.

Leaf spot is favored by cool, wet weather and spreads as spores are dispersed through rain, wind, mechanical or insects. Although the leaves look unsightly, leaf spot usually does not cause dieback on healthy trees; though trees that are under stress may have dieback after leaf spot becomes a problem.

If leaf spot is a continuous problem, a fungicide may be warranted. This product must be applied in early spring when the fungus is becoming active.

Disease Development Favored by:

  • Cool wet weather
  • Trees under stress

Corrective Measures:

  • Rake and destroy fallen leaves
  • Apply fungicide during bud break

leaf spot margins
Leaf Spot: note the border surrounding spot

Images By: Mary Burrows, Montana State University, Bugwood.org, David B. Langston, University of Georgia, Bugwood.org

If you believe your trees or shrubs have been affected with disease or fungus activity, call Grounds Services today for a no-obligations visit at 419-536-4344.