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
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

Dealing with live oak suckers in Central Texas
March 05, 2015 - Hi, I have a couple huge Live Oak trees in my back yard. Trunks are 4' in diameter. These Live Oaks produce a lot of root sprouts/suckers. I had always head that a tree's roots feed on water/oxyg...
view the full question and answer

Young pecan trees with leaf and branch problems from Gatesville TX
November 18, 2013 - I have a young pecan tree that had very rapidly browning Leaves. They became brittle and so did the branches with affected leaves. The branches soon fell off. We treated with fungicide during that pro...
view the full question and answer

Lantanas failing to bloom, turning brown
October 06, 2007 - The lantana in my front yard does not bloom, is not overwatered but does get watered, leaves turned brown and plants generally have not grown. The lantana in the rest of the yard are in bloom and lo...
view the full question and answer

Spots on just-emerging Zexmenia in Austin
April 02, 2010 - My zexmenia is just coming up from the ground after a cold winter in Austin. The leaves are all spotted with tiny holes as if something is munching on them before they even leave the ground or just as...
view the full question and answer

Chlorosis in sycamore in Kyle TX
August 04, 2011 - I'm trying to assist an elderly neighbor of mine with a plant issue. We have designated street trees in this community, our street being a Sycamore. The previous foreman out here called it a Mexica...
view the full question and answer

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