Host an Event Volunteer Join Tickets

Your gift keeps resources like this database thriving!

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?

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

Cotton root rot in Purple Sage, Leucophyllus frutescens
November 09, 2005 - We had three Purple Sage shrubs in our front yard. They did very well for about three years and then this past year they just died. From what I have read they are pretty hardy so we are really stum...
view the full question and answer

Problems with rock rose in Austin
June 10, 2013 - Hi Mr Smarty Pants, We have a Texas Rock Rose which is growing next to our gravel path in Austin, with grass growing under it. In the last week, it has stopped blooming suddenly, and all the leaves h...
view the full question and answer

Problems with non-native Chinaberry tree from Tucson AZ
September 05, 2013 - I have a 30+ year old Chinaberry tree and this year the branches are much sparser with leaves and there are a lot of small dead branches. Should I fertilize and what should I use? Thank you
view the full question and answer

Diseased Mexican plum tree in Austin
September 27, 2009 - I have a grove of 5 year old Mexican plum trees one of which is oozing sap from its trunk and a branch appears to have died. Is there anything that I can do to help the tree besides removing the dead...
view the full question and answer

Insect infestation of plants, dog and home
September 14, 2008 - I have plants that some kind of bug is killing them, my fan plam, ficus tree and other plants. The leaves are drying up and falling off. Apparently, they also are infestion my apartment. I feel them c...
view the full question and answer

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