So someone told us that the strange white spots appearing on our prickly pear cactus was an infection but not the kind we thought.
In fact it’s an infestation of cochineal bugs (Dactylopius sp.). These are tiny insects feeding on our cactus, hiding under fluffy white weblike wax, which helps protect them from predators and the elements.
These insects are crushed for a natural dye in some localities.
Or they kill your cactus. There’s a chemical spray that doesn’t always work. So I followed this person’s alternate instructions: Power wash off the webbing and spray the cactus pads with watery dish soap (unscented Dawn is recommended; not the lemon variety which is bad for the cactus.) The idea is that the bugs didn’t like to eat soapy cactus, or less likely, it poisons them when they try.
It was kind of interesting; I used a jet setting on my garden hose instead of a power washer. (I imagine a truly high setting might cut into the cactus pads). When I hit the white clumps just right they would not only wash off but also occasionally flash with a reddish purple burst of color as it presumably crushed the bugs inside.
Given that I didn’t know how to kill the bugs that would otherwise wash to the ground under the very cactus they liked to eat and might just climb back up, I was all for reducing the population.
A few days later it’s looking pretty good, time will tell. I expect there will be some stragglers. Hoping for some good luck.
P.S. Some message boards suggested using a toothbrush and soap on the individual pads, so if you have a smaller cactus collection and can actually get to all the pads, you can try that. I didn’t have that luxury of scale.
P.P.S. So I always talk about editing things, and my Google searches are no exception. I found this information throwing all the keywords I thought might be relevant, then edited them down and added others based on the results I was seeing.