En EspaŅol

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
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
Need help with plant identification, visit the plant identification page.
 
rate this answer
4 ratings

Tuesday - October 06, 2009

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders
Title: What is the sticky stuff coming out of the trees in Austin?
Answered by: Barbara Medford

QUESTION:

Hello - I live in Austin TX, and in the past half month or so, have been noticing much sticky, sweet sap being exuded from trees. In a normal year I only notice the crepe myrtles doing this, but this year we've seen copious sap dripping from our pecans, and also elms and mulberries around town. Car windshield are getting quite sticky! Is it an aphid or other insect? A friend thinks it may be the tree itself but I suspect that a tree would be unlikely to toss out such a resource, and especially across such a breadth of different species. Thanks for any help.

ANSWER:

There has been a lot of conversation about this problem this year, and it is most likely the result of aphids. There are a few other insects that can cause similar problems, but you are right, those trees are not likely to be squirting liquid. We don't know if the very extreme heat and drought has caused this, with the opportunistic insects attacking weakened trees, or if the insects are having an extremely good year. Ordinarily, when there is disease actually present in the trees themselves, you will see exudations from the bark, or signs of rot around the base, or leaves and branches dying.

There are several insects that can create the honeydew, that is, excretions from the insects that can cause this sticky rain. The honeydew, in turn, can be infected with a sooty mold, which is not particularly dangerous to the plant, but is unsightly and, if it gets too plentiful, can actually shade the leaves from needed sunlight. In this area, the most likely candidates for mess-making bugs are aphids, whiteflies, mealybugs and soft scale. We found a website that pretty well covers it all in terms of what can be done about these problems from the University of California Integrated Pest Management on Sooty Mold. Generally, the solutions are pretty low-tech: (1) ignore it, the leaves will be off the trees soon anyway, (2) give it a good spray of water and (3) try a good spray of soapy water. 

We'd like to say there was a permanent cure, but there isn't. They will all be back next year. Just hope we start getting enough rain to wash the little monsters off the trees without our having to use our precious water rations.

 

More Diseases and Disorders Questions

Sooty mold on Sophora secundiflora in San Marcos, TX.
September 23, 2010 - Dear Mr. SP, We have a Sophora secundiflora that is suffering with very black mold or fungus on most of its leaves. Last year, I washed it leaf-by-leaf with soapy water but it's getting too big t...
view the full question and answer

Problem with Prosopis glandulosa (Honey mesquite)
February 27, 2014 - One of our mature Honey Mesquite trees is losing thumb sized branches high up in the canopy because something is stripping the bark. The branches are completely white for 8-12 inches. Of course the ...
view the full question and answer

Live oak bark splitting in Katy TX
October 03, 2011 - We have a 7 yr old live oak that looks like its bark is splitting open in branches and top leaves look wilted. If that sounds like oak wilt, do we need to have the tree removed? We live in a subdivisi...
view the full question and answer

Reason for die-back of native Mahonia repens
April 01, 2008 - I have several mahonia repens plants planted on my property. This is the third spring for them and I have noticed that they look like they might be dying out. The leaves have turned brown and are cu...
view the full question and answer

Plants resistant to Verticillium wilt in Norco CA
September 24, 2009 - I'm looking for small trees, flowering shrubs & vines that are resistant to verticillium wilt. Fragrance would be a plus. Thank you so much!
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center