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
Not Yet Rated

Friday - September 28, 2012

From: Austin, TX
Region: Southwest
Topic: Diseases and Disorders, Cacti and Succulents
Title: Film growing on prickly pear from Austin
Answered by: Barbara Medford

QUESTION:

We've just xeriscaped our front & back yards. Two of the spineless prickly pear cacti have a beige film growing on the paddles. The film is now moving further up the cactus, and one of the upper paddles fell off yesterday. What do I need to do to prevent the film from growing, and to improve the condition of the plants?

ANSWER:

From CactiCare.com here is an article on Pests and Diseases of Opuntia, including Opuntia ellisiana (Spineless prickly pear). We are not clear on what the film is on your cacti pads but scroll down the page and look first at Cochineal Insects and then at Thrips.

From a previous Mr. Smarty Plants answer:

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!

 

From the Image Gallery


Spineless prickly pear
Opuntia ellisiana

Spineless prickly pear
Opuntia ellisiana

Spineless prickly pear
Opuntia ellisiana

More Cacti and Succulents Questions

Landscaping with native plants in Austin
October 06, 2005 - I'm expanding a flower bed in front of my house and would like to keep it all natives. 1) How do I find out what type of soil I should add? (I live near Hyde Park, Austin and haven't had a soil te...
view the full question and answer

Will a cut back yucca grow back in Lockbourne OH?
October 28, 2009 - I live in Ohio and recently I cut back all my plants to prepare for winter. I am wondering if my Yuccas will grow back. I cut them to ground level so only a little bit of the leaf is showing. I was...
view the full question and answer

Debugging and Preserving Dried Cholla Cactus
January 04, 2014 - Hi. Recently found an intact skeleton of a cholla cactus. I want to Bring it in our house. Are there any dangers associated with this, like bugs inside the "branches?" how would you suggest I prese...
view the full question and answer

Large agave (century plant) flower stalk
June 17, 2008 - HI.I live in Blythe, Ca. and have a GIANT of an agave in my back yard. It is now over 40'high and is blooming. I first noticed the stock growing at Easter when it was about 12' high. It is now t...
view the full question and answer

Monocarpic plants for Indiana
October 06, 2005 - We were in Hawaii this summer and became acquainted with the Silversword. This plant (according to what we were told) blooms only once in it's lifetime (of 50-70 years). Are you aware of any other pl...
view the full question and answer

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