Saturday, August 23, 2014

What's this sooty stuff on my trees?

Sooty Mold

Another beautiful day in Illinois. You take a nice stroll through your yard and notice this awful black, sooty stuff on your trees. Gross! Although hideous in site, it is probably of no concern to your plant's
health. It is likely that the black stuff you are seeing is sooty mold. Sooty mold is caused by several different fungi. The fungi don’t infect plants, but grow on the sugary honeydew excreted by aphids, scales and other insects.

Where can I find sooty mold?

In Iowa and Illinois, sooty mold is most common on maple, pine, linden and elm trees. While sooty mold can reduce plant vigor by blocking sunlight and interfering with photosynthesis, the damage is mainly aesthetic. Sooty molds are associated with high temperatures and increased stress brought on by limited moisture. During drought, aphid populations and their honeydew production typically increase on foliage undergoing moisture stress.  So, keep plants well watered and free of insects.

What should I do about it?

It is not necessary to control sooty mold as it does not cause serious harm to healthy, well established trees.

In addition, it’s usually not necessary to control aphid and scale infestations on trees with insectides. Damage to healthy trees is seldom serious. Plus, natural enemies and weather usually provide adequate control of scale and aphids. However, to control the infestation reduce the population of
sucking insects that excrete honeydew. Use the appropriate recommended chemicals that control aphids and other sucking insects. Also, a good washing of infested tree's foliage (if possible) can dilute the honeydew and wash off mold. That just may be all that is needed.

To help you diagnose your tree's problem, whether it is sooty mold or any other tree disease, treat it and keep it healthy for years to come, it is recommended you consult with your local tree service.

Trees "R" Us, Inc. is a professional tree service in the Chicagoland area. We service the north shore, north suburbs and northwest suburbs of Chicago. Trees "R" Us, Inc. has 4 certified arborists on staff ready to assess your plants and tree care needs in a timely manner. Our services include tree trimming, pruning, stump grinding, emergency tree services, tree removal, cabling and bracing, fertilization and plant health care.

Trees "R" Us, Inc. can be contacted at 847-913-9069 or through our online forms at

Thanks for reading,


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