Signup to receive email updates
Recent Posts
Categories
Links
Blog Archives
- February 2019 (3)
- January 2019 (5)
- December 2018 (4)
- November 2018 (4)
- October 2018 (5)
- September 2018 (4)
- August 2018 (5)
- July 2018 (3)
- June 2018 (4)
- May 2018 (3)
- April 2018 (4)
- March 2018 (5)
- February 2018 (2)
- January 2018 (4)
- December 2017 (4)
- November 2017 (3)
- October 2017 (5)
- September 2017 (4)
- August 2017 (5)
- July 2017 (4)
- June 2017 (4)
- May 2017 (5)
- April 2017 (4)
- March 2017 (5)
- February 2017 (2)
- January 2017 (7)
- December 2016 (3)
- November 2016 (3)
- October 2016 (5)
- September 2016 (4)
- August 2016 (4)
- July 2016 (5)
- June 2016 (4)
- May 2016 (4)
- April 2016 (4)
- March 2016 (3)
- February 2016 (4)
- January 2016 (6)
- December 2015 (3)
- November 2015 (3)
- October 2015 (4)
- September 2015 (4)
- August 2015 (4)
- July 2015 (5)
- June 2015 (4)
- May 2015 (3)
- April 2015 (3)
- March 2015 (3)
- February 2015 (4)
- January 2015 (5)
- December 2014 (4)
- November 2014 (2)
- October 2014 (3)
- September 2014 (4)
- August 2014 (4)
- July 2014 (4)
- June 2014 (3)
- May 2014 (3)
- April 2014 (2)
- March 2014 (2)
- February 2014 (4)
- January 2014 (2)
- December 2013 (4)
- November 2013 (5)
- October 2013 (4)
- September 2013 (3)
- August 2013 (5)
- July 2013 (4)
- June 2013 (4)
- May 2013 (4)
- April 2013 (4)
- March 2013 (4)
- February 2013 (2)
- January 2013 (4)
- December 2012 (4)
- November 2012 (5)
- October 2012 (4)
- September 2012 (3)
- August 2012 (5)
- July 2012 (4)
- June 2012 (4)
- May 2012 (4)
- April 2012 (4)
- March 2012 (6)
- February 2012 (3)
- January 2012 (4)
- October 2011 (1)
- June 2011 (1)
- January 2011 (1)
- December 2010 (1)
- November 2010 (2)
- October 2010 (1)
- August 2010 (3)
- July 2010 (2)
- June 2010 (2)
- May 2010 (2)
- April 2010 (1)
- March 2010 (1)
- February 2010 (2)
- January 2010 (2)
- December 2009 (2)
- November 2009 (1)
- October 2009 (2)
- September 2009 (1)
- August 2009 (5)
- July 2009 (2)
- June 2009 (2)
- May 2009 (1)
- January 2007 (1)
374 Total Posts
follow our RSS feed

Monday, July 24, 2017
Tree Foliage Diseases and Galls
Now that nearly every shade tree and ornamental are in full leaf, gardeners have been spotting some "spots" out there. Those spots can range in color from light green on a very green leaf (oak leaf blister) to black dots coming together to give a much larger blotch of black (tar leaf spot on maples).
In general, leaf spot diseases are rarely fatal to a tree so that is good news. What is often disturbing is those spots appear on the lower branches, right at eye level for all to see, especially while we sit on the patio chairs gazing out into the home landscape. These spots can also deform the shape of the leaf, causing a curling or appear raised or sunken on the leaf surface. About the only time a fungal leaf disease can be impactful is if every leaf is covered on a young seedling.
Homeowners also are spotting galls. Galls show up as the leaf develops. Typically, a gall-forming insect will lay its egg(s) right into swelling bud scales in early spring, as the leaves are ready to emerge. Many oak galls do this. Instead of a leaf, the egg transforms the leaf tissue into a thick walled gall or a portion of the leaf is transformed. The egg hatches and the young larvae consume the gall from the inside out through its various stages, and the adult emerges via a small hole in the now hollowed out gall.
Earlier this spring, silver maples were seen with the Maple Bladder Gall Mite creating small bright red galls that later turn black when the mite emerges. They occur in large numbers usually. The Spindle Gall is more solitary with only several on any one leaf and sticks up off the leave nearly half an inch. Just like the leaf spots, a plant would need to be covered before a treatment may be warranted.
If leaf spots and galls have been heavy this year, then planning now for next year is in order if they are to be prevented. Since leaf spots and galls get started early in the spring, the treatments are needed then to protect the plants. Foliage leaf spots invade new developing tissue as the leaves just begin to emerge from the overwintering bud scales. Gall forming insects can lay eggs in those same buds and on young emerged tissue.
Leaf spots are a fungal disease and a fungicide would need to be applied preventing fungal spores from invading that tender tissue. Similarly, an insecticide or miticide, depending on the insect, would need to be used for galls. Since some of these insects overwinter right on the tree in bark crevices, thorough coverage is needed.
The bottom line here is most of these problems are not life threatening to the trees, and if you are going to prevent them, timing is everything!
Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Stay tuned to more garden and yard updates with "This Week in the Garden" on Facebook at facebook.com/extensiondkk/videos. The 2017 Kendall County Master Gardener Help Desk currently is open Monday, Wednesday and Friday from 9 a.m. to 12:30 p.m. at 630-553-5823 or at uiemg-kendall@illinois.edu.