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
Not Yet Rated

Sunday - March 25, 2012

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders, Cacti and Succulents
Title: Black fungus on cholla cactus from Austin
Answered by: Barbara Medford


How to get rid of black fungus on cholla cactus? Cut it off? And treat with what?


Cylindropuntia imbricata (Tree cholla) is native to Texas but not, as this USDA Plant Profile map shows, native to Travis County. However, if you are willing to provide the proper environment, there is no reason why it should not flourish. Here is an article with numerous pictures from Southwest Colorado Wildflowers; no mention of fungus, however, so we will look a little further.

We think you'll find the comments on this plant in this Dave's Garden forum interesting, especially considering the weather conditions they can survive, but still no fungus cures. From the Sonoran Desert Digital Library, more information on the plant.

Finally, a website mentioning fungus: from Arizona Cooperative Extension Pests of Agave, Aloe, Cactus and Yucca. Scroll down to Page 6, where you will find "Fungal diseases of leaves and pads." On Page 7, we found a section on Insects which included this description of the Cactus Longhorn Beetle:

"This beetle attacks several species of cacti including prickly pear and cholla cactus (Cylindropuntia species), barrel cactus (Echinocactus and Ferocactus species), young saguaro cactus (Carnegiea gigantea), and others. The adult beetle is about 1 to 1¼ inches (2.5 - 3 cm) long, shiny black, and has distinctive white markings on the antennae. The antennae are often longer than the overall body length of the adult beetle. Damage to the plants is the result of feeding on the margins of prickly pear pads or terminal buds of other cacti (Fig. 18).

Cholla cacti are attacked by the beetle when the adults lay their eggs, hatch and the larvae burrow into the stems. Waste (frass) is pushed out the entry holes and forms a black crusty deposit on the canes. Larvae may burrow into plant roots and cause collapse and death of the plants.

Cactus longhorn beetle is controlled by hand picking the insects off infested plants. The beetles are most active and easier to detect and destroy in the early morning or late evening, especially after warm summer rains. Very spiny species are less likely to have damage from the beetle due to a natural defense by the spines. Chemical control is not recommended since the populations usually are not high and hand picking is effective."

This may or may not be the situation with your cholla, but the pictures throughout the article are excellent and you may well find your problem somewhere else in it.

From the Arizona Department of Agriculture, we found Bacterial Necrosis of Saguaro Cactus. This article states that the same condition has been noted in cholla cacti. It gives instructions on cutting out the rot and treatments for it. Again, since we are not plant pathologists and cannot see the cactus, you will have to be the judge of which treatment, if any, you wish to use.


From the Image Gallery

Tree cholla
Cylindropuntia imbricata

More Diseases and Disorders Questions

Trimming oaks and elms from New Braunfels TX
June 20, 2012 - I would like to trim my live oaks and elm trees at the same time, if possible. I think they are American Elms. When is the best time to do this and avoid oak wilt and Dutch elm disease? Should all c...
view the full question and answer

Problems with morning glory in Tennessee.
June 09, 2009 - I recently moved to Tennessee from Michigan. On my property I have a perennial morning glory. This year the leaves are all bubbly, the stems have white hard stuff on them and there is a brown hard t...
view the full question and answer

Cedar elm with brown leaves
August 12, 2011 - Dear Mr. Smarty Plants, We feel we may have limited time to save our beautiful Ceder Elm. We have many trees in our yard (Post Oaks and Cedar Elms) and have been told they are all between 50 - 75 year...
view the full question and answer

Problems on Prickly Pear Cactus in Illinois
November 19, 2014 - I have a fungus on my prickly pear cactus that is not a bug. I tested it and my fingers didn't turn red when I squeezed them. So how do I get rid of this as it is spreading to my other cacti?
view the full question and answer

Oak sap dripping on driveway in Austin
November 06, 2011 - Why would oak sap be dripping on driveway at this time when other oaks the neighbors have are not.
view the full question and answer

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