Host an Event Volunteer Join Tickets

Support the plant database you love!

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
1 rating

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

QUESTION:

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

ANSWER:

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

Apparent disease in peach tree in Austin
June 12, 2008 - I have a peach tree that the leaves are "bleeding" out on. The leaves are continuing to get paler and paler. There are no peaches on the tree this year either. What can I do?
view the full question and answer

Mountain Laurel slowly dying in San Antonio, TX
December 26, 2012 - My Texas Mountain Laurel seems to be dying in a slow unusual manner. Over the past two weeks the leaves have been turning yellow and falling off starting with the south facing side of my multi-tru...
view the full question and answer

Protection of American beautyberry in Pennsylvania
July 30, 2007 - I have had a beauty berry 2 years now. I trim it back in early spring and it returns beautifully. ...but no flowers this year and it's almost August. Last year, very few berries. Can you help? I...
view the full question and answer

Keeping dogs and cats out of flower gardens
March 02, 2009 - Do you have any suggestions to keep the cats and dogs out of my flower garden? They either just walk through it, and trample everything, or sleep on the soft blooms and squish everything. I am despe...
view the full question and answer

Insect pests in Gaillardia aristata in Tennessee
August 22, 2008 - Dear Mr. Smarty Plants, I have a couple of 'Oranges and Lemons' blanketflower plants in a butterfly and hummingbird native flower garden that is the foundation planting of my house. They bloom prol...
view the full question and answer

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