Rent Shop Volunteer Join

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
1 rating

Wednesday - July 25, 2007

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Oak diseases as a result of wet, cool weather
Answered by: Damon Waitt

QUESTION:

The mature live oak trees in our back yard have been dropping leaves just like they do in March, but this is July! Small to medium spots on the leaves turn brown before they drop. The veins of the leaves are still green. The trees are growing on a well-drained slope in shallow soil over limestone here in the hill country just west of Austin. Asiatic jasmine grows under some, but not all, of the trees. This has never happened in the past 13 years. Does it have to do with the heavy rainfall? Will they survive? Do we need an arborist consult?

ANSWER:

It is our good fortune that James Houser, the Texas Forest Service Oak Wilt Technical Coordinator, recently addressed this question on the texasoakwilt.org website. You can click here to view a pdf version of his article with images.
"Abundant rainfall and cooler than normal temperatures this spring and summer, oak trees are infected with a variety of leaf diseases that cause significant discoloration of leaf tissues and defoliation. Symptoms include a spotting and/or yellowish mottling of the leaf tissue, blistering and deformity of the leaf margins, small twigs with brown leaves randomly distributed within the tree canopy, and small gold fruiting structures on the undersides of leaves. The trees are frequently shedding these leaves as the leaf disease matures.

Diseases that can be responsible for these problems include Actinopelte spp., Oak leaf blister, Diplodia spp., Anthracnose, and Oak rust among others. These problems are only confined to the leaf tissues, though with Diplodia spp. small twigs an inch or two long die. Branches remain alive and viable on the tree for new leaves to form. The trees are not dying. Fungicides are ineffective at this point as new infections do not occur with elevated night temperatures during the summer. Raking up and disposing of the leaves on the ground is a good strategy to remove the local inoculum. This is a natural occurrence during high rainfall years and the trees will recover on their own.

This is not oak wilt. Oak wilt leaf symptoms are completely different. Also a pattern of mortality in the stand of trees over time is not apparent, i.e. an infection center radiating out over the landscape for several years. Trees in Texas encounter many problems from our stressful weather conditions. Last year, drought was responsible for damage to the trees. This year too much moisture plays a role. Yet, trees, especially oaks, are tough. They go through these cycles of nature and keep on growing."

 

More Diseases and Disorders Questions

Older leaves yellowing on Savannah holly in Dallas
May 01, 2009 - I planted a Savannah Holly in Dallas, TX in the Fall of 2008. It has new growth and some white buds all over it, but some of the older leaves are turning yellow and dropping off. Is this normal?
view the full question and answer

Leucophyllum Resistant to Verticillium Wilt
March 25, 2015 - I need to know which large shrubs are resistant to verticillium wilt? I believe that a few of our Elaeagnus have succumbed to this disease, but being over 15 years old, I am not positive. I am thinki...
view the full question and answer

Leaf drop from maple tree in Minnesota
August 15, 2008 - I have about a 30 ft maple tree in my yard, last fall I trimmed it pretty good because the branches were getting low where you could not walk under it or get grass to grow. This is the 2nd time in abo...
view the full question and answer

Elaeagnus sudden death in Waxahachie, TX
May 11, 2015 - I live in North Central Texas and have eleagnus planted along my fence in full sun. Last year one dropped all it's leafs and died. The same is happening to one beside it this year. I have sprayed ...
view the full question and answer

Problems with a two year old persimmon tree in Fredricksburg, TX.
May 22, 2013 - Hi Mr/Ms Smarty Plants, We planted a 4-ft Texas Persimmon, Diospyros texana, 2-years ago, with wonderful leaf and fruit production since. We recently had a hail storm (5/9/13) and although mos...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.