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?

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
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
Not Yet Rated

Monday - February 25, 2013

From: Plum, TX
Region: Southwest
Topic: Non-Natives, Diseases and Disorders
Title: Black Sooty Mold on Bay Tree
Answered by: Anne Van Nest

QUESTION:

I have a large bay tree and all the leaves are covered with a black mold-like substance on the top part of the leaf. Under each leaf are some black/brown spots. I have washed the leaves with soap and water using a wash cloth. This cleans the leaves some but this stuff is stubborn. I really do not want to hand wash 1000+ leaves. I have tried fungus sprays, mold spray, and high pressure washing with just water. Nothing seems to help. All the new growth is getting the same gunk. Help!

ANSWER:

Sorry, bay laurel trees (Laurus nobilis) are a little out of our line since they are native to the Mediterranean. The Lady Bird Johnson Wildflower Center, home of Mr. Smarty Plants, is committed to the growth, protection and propagation of plants native not only to North America but to the area in which they are being grown. In Texas, this is Texas A&M. Below though are links to several websites which we believe have the information you are looking for. Look at the Texas A&M AgriLIFE Extension web page on bay laurels.

Your plant symptoms though are similar to what sooty mold does when it attacks some native plants. The sooty mold grows on the honeydew that is excreted by small soft-bodied aphids or scales that suck sap from plants. In your case there is a laurel aphid that attacks bay laurel trees and excretes a sticky, sugary substance that drips down onto the tops of lower leaves. Soon thereafter, a black, mold grows on the sugar. The sooty mold blocks the light to the leaf and weakens the plant.

Look for small pale green insects (aphids) on the new growth or small round bumps (scale) to find the ultimate culprit of the problem.  Once you have determined the honeydew cause (and solved this problem), you will be able to get your mold under control. For more information look at this ehow article on bay laurel tree problems.

 

More Diseases and Disorders Questions

Sap dripping from a lacey oaks in San Antonio
September 06, 2012 - I have a lacey oak tree, approximately 6 ft. tall that has been in the ground almost a year. The tree looks healthy but there is a small area on the trunk that looks and feels wet. The substance is s...
view the full question and answer

Watering Houseplants with Soapy Water
August 22, 2011 - I accidentally watered my house plants with a container that had a some dishsoap in it. Will they be okay? One of the plants is a 20yr old cactus, with small roots.
view the full question and answer

Black leaves and dying kinnikinnick (Arctostaphylos uva-ursi)
December 16, 2007 - My kinnikinnick has developed dark leaf spots and, in some cases the entire leaf has turned black or entire plants have turned black and died off. I'm worried about leaf spot, root rot and leaf gall...
view the full question and answer

Sap dripping from redbud in Bertram, TX
March 03, 2014 - Our multi-trunked Texas redbud has sap dripping down 3 of the trunks. It seems to originate from a very small crack in each trunk. The tree is just starting to show pink this week, and is about to blo...
view the full question and answer

Round growths on Mexican buckeye
April 28, 2008 - I have two pink buckeyes next to each other in my yard. The branches on one are completely covered in brown, round growths about the size of a pill bug. The other tree has none. Can you tell me what t...
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.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP | STAFF
© 2015 Lady Bird Johnson Wildflower Center