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?


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
2 ratings

Sunday - February 25, 2007

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Control of sooty mold from aphids in Crape Myrtle
Answered by: Joe Marcus


I have a crape myrtle in my front flower bed that has a sooty black substance on the leaves and trunk. I've done research and understand this is caused by aphids. My question is how do I get the black sooty substance off the tree and what do you recommend for getting rid of the aphids?


Sooty mold is a fungus, or more commonly a complex of two or more fungal species, that grows on honeydew or on plant exudates. Honeydew is a waste-product of aphids and other plant-sucking insects. As honeydew is excreted by sucking insects, it falls and coats any surface upon which it lands. Sooty mold fungi invade and live upon this sugary coating. These fungi do not infest the leaf ifself. Thus, sooty mold may often be found growing on any exposed surface beneath aphid-infested trees and shrubs. Sooty mold can cause great harm to plants, however, by blocking sunlight to the leaf surface below and diminishing photosynthesis.

Sooty mold can often be successfully removed by rinsing with water from a garden hose. However, this will be most effective after the aphids or other honeydew-producing insects are destroyed. Sometimes sooty mold development is so severe and persistent that only time and exchange of leaves through the growing seasons will remove it all.

Aphids are not especially difficult to control and non-chemical methods are usually very effective. Insecticidal soaps are often the remedy of choice for many gardeners. Various brands of insecticidal soaps may be found at just about any retail nursery or garden center. Be sure to read and carefully follow all label directions when using any pesticide, organic or chemical.


More Diseases and Disorders Questions

Mildew in Phlox paniculata
October 13, 2008 - I planted garden phlox (phlox paniculata) in my front landscaping and it is suffering from mildew. It is wet on that side due to a down spout and it may benefit from being split. Does anyone know of...
view the full question and answer

Damaged leaves on bottlebrush buckeye from Glen Mills PA
June 09, 2013 - My recently planted bottlebrush buckeye plants' leaves are looking damaged but it doesn't look like insect or fungus damage. They look battered by wind but I don't understand why that would happen...
view the full question and answer

Newly planted anacacho leaf browning
October 15, 2007 - I have just put my anacacho orchid into the ground and its leaves are turning brown and falling off. Is that normal for this time of year, or have I shocked it? What can I do to ensure its health?
view the full question and answer

Information about giant yellow and black wasps
September 13, 2008 - Regarding a previous question submitted by a person asking about the giant yellow and black wasps..It's a Cicada Killer.I used to see them all the time when I was a kid in Victoria, Tx..But I haven'...
view the full question and answer

Rust problems on Jack in the Pulpit in IL
June 12, 2011 - The last 2 years I have noticed that some of my jack in the pulpit plants have something that makes me think of a copper color rust.It seems to start on the underside of the leaves. What can I do to g...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2015 Lady Bird Johnson Wildflower Center