The Q&A Archives: White Clumpy Fungus Like Substance On Prickly Pear Cactus

Question: I have some 10 year old prickly pear cactus that are getting this white clumpy growth all over the cactus pads. From a distance it looks Styrofoam or cottage cheese. I have sprayed it off. Should I treat it with something?


The large masses of white wax that appears on the pads of some prickly pear cactus is insect related. The wax comes from an insect common to the Sonoran desert called "cochineal scale."

Cochineal is a tiny red sucking insect that draws the fluid from pads of prickly pear. As they feed, they produce masses of a white waxy material as a coating to help protect them from predatory insects and birds looking for a tasty meal.

If the infestation of cochineal scale is light, you can save the pads by spraying away the protective wax with a garden hose. After the pads dry, spray a soap solution on the now-exposed scale to kill them. An effective soap solution is two tablespoons of liquid dishwashing detergent to one gallon of water.

Untreated, cochineal scale can do significant damage to the prickly pears they feed upon and control measures are advised. Pads that are heavily covered with wax and scales should be pruned off and removed.

Don't remove just part of the pad by cutting it in two. Prune where the joint of one pad meets another. In some cases, this may require removing most of the pads and allowing the cactus to re-grow.

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