En Español

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

Blackening of top growth of yaupon in Sunrise Beach TX
June 09, 2010 - My question regards a Will Flemming yaupon which I am thinking may be within your scope of expertise. These were recently planted under windy conditions, then hit with a neighbors antiquated jet type ...
view the full question and answer

Hypoxylon Canker removal in Austin TX
March 26, 2012 - I have several oaks that appear to have been killed by Hypoxylon atropunctatum from last summer's drought. Is it safe to cut them down in March or does that risk spreading Oak Wilt too. Should I ...
view the full question and answer

Survivability of plants after freeze
December 08, 2003 - I have many beautiful plants that froze. Some were Lantana, Hummingbird Bush, Candlestick Trees, Esperanza, Some flowers, and Marigolds. I love all of my plants and flowers and I want them to grow bac...
view the full question and answer

My Mock Orange fails to flower in Redmond, WA.
July 06, 2011 - I planted a Mock Orange shrub about 5 years ago. The first few years, it only produced leaves but no blossoms. Then, last year, it finally produced 4-5 blossoms on 2 of the branches. This year, it a...
view the full question and answer

Red-backed bugs on mountain laurel (Sophoro secundiflora)
May 12, 2010 - I found red-backed bugs (in fact two end-to-end like the east Texas love bugs) on my mountain laurel which has been losing leaves. Are these bugs the culprit?
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center