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
1 rating

Tuesday - November 18, 2008

From: Los Angeles , CA
Region: California
Topic: Cacti and Succulents
Title: Cochineal bugs on cactus
Answered by: Nan Hampton


Mr. Smarty plants. I have purple prickly pear cactus that are developing small white flake like spots, mostly where the thorns would be. Why is this happening and how can I cure it?


Your cactus sounds as if it is infested with cochineal bugs (Dactylopius sp.).  They are small scale insects that feed on the cactus.  They produce fluffy white wax that hides their bodies as they feed on the cactus and protects them from the elements (drying out, in particular) and from predation.  The fluffy wax also serves as a sail or balloon to float on the wind and take the bugs to a new patch of cactus.  The bugs produce carminic acid that also helps protect them from predation, especially from ants. This carminic acid in the bugs has been used by indigenous peoples of southwestern North America, Central America and sub-tropical South America to make a brilliant red dye for centuries, perhaps millennia, to produce beautifully colored textiles. Originally, the cochineal bugs were limited to the New World.  When the European explorers visited and saw the beautiful red cloth of the natives, they took the cochineal bugs back with them and now they occur all over the world.  When a synthetic red dye was produced the demand for cochineal bugs decreased, although they have also been used to help control cactus popuations.  Recently, however, after it was determined that the synthetic red dyes can have adverse health side effects, there has been a renewed  interest in growing cochineal bugs for red dye.  The dye made from the bugs is currently used in cosmetics and as food coloring.  Because of this, controlling cochineal bugs hasn't really been a priority and, therefore, there isn't a lot of information that I have been able to find for controlling them.  However, click here to read what one grower recommends.  If your infestation is small, I suggest scraping them off (carefully, to avoid the sharp cactus spines) and disposing of them.  You might also be able to wash them off with a water under pressure.  Test a small area first to be sure that you don't injure your cactus and gather up and dispose of any of the insects that you wash off the cactus.

Here are a few links to more information about the cochineal bugs:

Gateway to Sedona with a bit the history of the using the bugs for dye.

Wayne's World with excellent photos of the bugs.

You can read instructions for making and using a natural dye from the cochineal in Using the Cochineal Bug and Dying Things Red!!


More Cacti and Succulents Questions

Saving frozen yuccas from North Carolina
February 23, 2013 - I live in NC and have 2 potted yucca plants on my deck. Every year I have brought them in for the winter. This year, someone told us that we could leave them out all winter. They began to die in the c...
view the full question and answer

Sunny and shady lawns from Austin
April 28, 2012 - My front yard has a large bed surrounded by a mix of St. Augustine and Bermuda grass. Last summers heat killed off about 90% of the St. Augustine, which we would like to replace anyway to conserve re...
view the full question and answer

Failure to bloom of red yucca from Lago Vista TX
April 09, 2013 - I am in Lago Vista - trying to find out why I can't get my red yucca to bloom. The first year they were great and now after two or three years - no measurable spikes have shown up. HELP!
view the full question and answer

Replacements for yuccas from Georgetown TX
August 07, 2013 - I have lost some softleaf and variegated yucca to a beetle grub destroying the root system - like the Agave snout beetle does. I have put an insecticidal drench on my remaining plants, but suspect wi...
view the full question and answer

Dead leaves on yucca in Georgetown TX
October 18, 2010 - We have 2 6ft and 3 smaller soft leaf yuccas out back in a kidney shaped area with a wax myrtle and a mountain laurel. The yuccas have done great but now two of them have a large number of dead leaves...
view the full question and answer

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