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
1 rating

Tuesday - June 03, 2008

From: Los Angeles, CA
Region: California
Topic: Diseases and Disorders
Title: Brown flakes on prickly pear in Los Angeles
Answered by: Barbara Medford

QUESTION:

I live in Los Angeles CA. I have desert type plants in my landscape. I have prickly pear cactus that have developed some light brown, almost golden flakes on the skin of the pads. I believe it is called scurf, or dandruff. I have searched on the web and found descriptions of fungi on cactus as being black spots. I have brown flakes. What can I use to treat / remove and stop the flakes from spreading on to the other cacti? Please let me know

ANSWER:

There are nine prickly pears in our Native Plant Database; three of which are found in California. This doesn't necessarily mean one of those three is what you have, it's just a way of narrowing down the number we look at. They are all in the Genus Opuntia so if we can establish what problem matches your description, it will probably be true throughout the Genus.

Opuntia engelmannii var. engelmannii (cactus apple)

Opuntia phaeacantha (tulip pricklypear)

Opuntia polyacantha var. erinacea (grizzlybear pricklypear)

USDA Plants profile for Opuntia polyacantha var. erinacea (grizzlybear pricklypear) with pictures.

The Plant Pathology Lab of Texas A&M has released a list of Opuntia diseases. Here are some extracts from that article:

Cactus Anthracnose (fungus - Colletotrichum (Gleosporium) spp.): This disease affects several kinds of cacti, Cereus, Echinocactus, Mammillaria, and particularly Opuntia (prickly pear). Infection results in a rather moist light brown rot which shows many light pink pustules on the surface. Spots are small at first, later enlarge and become covered by the small spore-producing pustules. Large areas may be affected, sometimes destroying entire plants. No satisfactory control is available, other than removing and destroying diseased cladodes as soon as noticed. In the greenhouse, soil from infected plants should be removed and benches disinfected. Spraying with a copper fungicide may help in checking the disease.

Scorch or Sunscald (fungus - Hendersonia opuntiae): This disease is common and serious on prickly pear cactus (Opuntia). Spots at first are distinctly zoned, later enlarging until entire cladodes turn a reddish-brown and finally die. The center of the disease area is grayish-brown and cracked. Other fungi may also be present in the diseased area. No practical control has been developed.

Scab (physiological): Particularly common on prickly pear cactus. Rusty colored, corky areas appear on the stems. Scab is thought to be a form of edema, resulting from overwatering and poor ventilation. Increase light and decrease humidity for control.

Stem Rot of Cacti (fungus - Drechslera cactivorum): Basal or top rot of seedling cacti that turns cactus into a shrunken mummy covered with brown spores. First symptoms are yellow spots. It can completely rot a plant in four days. The fungicide Captan should give some control.

Doesn't sound good, does it? We searched for pictures of the various diseases on a prickly pear, so you could compare them, but didn't find any. In fact, virtually every search phrase we used returned us to the article from Texas A&M that we have already referenced. On a couple of discussion websites, we found that Opuntia is considered by many an invasive weed, and no one seemed too interested in curing its diseases.

Summary: See each disease for suggestions for treatment, usually, cutting out the diseased portion and disposing of it in a way to prevent the disease being passed to others. Scab may be caused by watering the cactus, having it in too much shade and/or poor circulation. So, you could move it to a better location-now there's a challenge!


Opuntia engelmannii var. engelmannii

Opuntia phaeacantha

 

 

 

 

 

More Diseases and Disorders Questions

Black rot at center of Agave from Clovis CA
May 12, 2013 - We have some beautiful variegated "Green & Cream" Agave plants in our cactus garden. One in particular has done quite well for several years and is the largest, about 18" tall & across, it has neve...
view the full question and answer

Problems with yaupon from San Angelo TX
April 08, 2012 - We have a 3-yr-old yaupon holly entering its 3rd summer. We have put store-bought wood-chips under the tree several times since it was planted. A plant has grown under the tree, possibly out of the ...
view the full question and answer

Insects on hybrid 'Ann' magnolia in Morrow OH
June 17, 2010 - I have an Ann Magnolia. It is covered in all kinds of stinging insects and flies. This has never happened before. Is this a common problem for the tree? What should I do?
view the full question and answer

Fungus Spots on Native Bush Honeysuckle
December 03, 2010 - My native bush honeysuckle plants that I have along my back fence have leaves that are turning yellow with spots. It appears to be a type of fungus, but not powdery mildew. Any suggestions as to what ...
view the full question and answer

Keeping cows from eating the garden
September 02, 2008 - I have a flowerbed area outside of our new split-rail fence available for planting, but cattle roam outside the fence also! Do you have any suggestions for plants that cows tend not to eat (unle...
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
© 2014 Lady Bird Johnson Wildflower Center