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
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

Bark damage to Tulip Tree
August 10, 2006 - I have a tulip tree planted. It is about 9-10 years old. Two years ago the tree looked as though the trunk was cracked. Maybe hit by lightning after a storm. This year the bark on the side of tree...
view the full question and answer

Freeze-damaged Texas Mountain Laurel in Austin, TX.
May 05, 2011 - I have a Texas Mountain Laurel (Sophora secundiflora) that is several years old. During this past winter, one of the freezes we had split one of the largest trunk right below the soil line. T...
view the full question and answer

Sooty Mold on Beauty Berry
May 19, 2009 - We recently planted a beauty berry plant (among others) to attract birds in our backyard. We have had a lot of rain (probably 5-7 inches) since planting a few weeks ago if that might have something to...
view the full question and answer

Hybrid Leyland Cypress leaning in Annapolis MC
June 29, 2011 - We have a large, 9-year old Leyland Cypress that has tipped over. It is still green and growing but leaning slightly off center. It's about 20' tall. Should we stake it? If so, we'd like to do ...
view the full question and answer

Leaf problems on oaks in North Liberty IA
June 12, 2010 - My oak trees (young and old) are showing leaf problems. Is there a disease or insect causing oak tree disease?
view the full question and answer

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