Explore Plants

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
    
 

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

QUESTION:

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?

ANSWER:

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

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

Brown rings on grass under live oaks in Austin
June 13, 2013 - There are brown rings in the grass at the dripline on several Live Oak trees in our neighborhood. What causes this? The trees appear healthy.
view the full question and answer

Problems with Cedar Elm in Austin, TX.
August 04, 2012 - Our Cedar Elm has yellowing very dry leaves and something is eating the topmost leaves leaving holes and obviously chewed off leaf segments. Could this be two different things? Aphids and bacteria or ...
view the full question and answer

Trees failing to prosper from Denham Spring LA
December 23, 2013 - I live in Louisiana. Out of all of the native trees that we grow, there are two in particular that always struggle no matter what the conditions are in which they grow. The first one, sassafras, is ...
view the full question and answer

Cupressaceae dying in Suffolk Co.NY
October 20, 2012 - I have noticed that all of my Cupressaceae (& others I see in my area) are dying. They turn yellow, then rust & brown til they are everbrowns. what is going on?
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.