It could be mealybugs; I can't tell from yout photo (sharp close-up may help...). If mealybugs (scale is also a bug that could infest opuntia), there is often fine web. You could test it: get a q-tip & moisten it with rubbing alcohol. Dab right on. If bugs, they will die on contact. Mealybugs have white protective covering that will immediately dissolve & tiny orangey bug will die too. Scale has thicker armor, but will also die & wipe off. Large infestation, as it appears to be on your plant, may not be easy to get rid off.

It could be also a fungal disease, so make sure to determine what it is...

Does this picture help? I tried using a q-tip with rubbing alcohol and nothing has happened yet.

Helps some...I would think meaybugs...alcohol works immediately, but has to be directly on the bug. How strong is it? It could be also sprayed on. Or, use a tissue if sqeemish, and press directly on the bug. There will be pinkish stain; mix of blood+guts+die...(+dead bug)

That is quite extensive infestation & should be treated asap. And isolate the plant (bugs will spread). If spraying with anything, keep plant out of direct sun

Thanks! The infestation pretty much all happened over night. I had set it down in my garden to get sun while I waited on my grow light to get here and when I brought it back up it was like that. Just went and got a spray bottle, gonna give those bugs hell 😂.

I tried using 91% isopropyl in a spray bottle with no luck. Additionally, I tried taking tweezers and taking the infestation off that way but that seemed to expose the inside of the cactus pads.

Alex

It looks really like bugs to me, but I don't think they will happen in such numbers overnight!

Maybe it is some fungus??? Bugs would definitely die if using alcohol. They can be wiped off.

Do not force it off with tweezers - pads get damaged.

Maybe you put it into strong sunlight suddenly?

There are also bacterial or viral diseases.

That may be it - I got the cactus from PlantVine and they said to water and put in to sunlight as soon as unboxing. Do you know what fungus or disease that may have caused?

rina_Ontario,Canada 5a : When spraying for mealies, how many days before I can expose the plant to sunlight again?

hellkitchenguy Manuel

I would keep it out of the direct sun few days after the last spray - often, repeat treatment is needed. Rubbing alcohol dries off very fast, but I still would keep plant out of direct sun for a day....

Alex

There are few that appear on opuntia; see link attached (https://plantdiseasehandbook.tamu.edu/landscaping/flowers/cacti-and-succulents/#:~:text=Scorch%20or%20Sunscald%20(fungus%20%E2%80%93%20Hendersonia,is%20grayish-brown%20and%20cracked.)

Could never find out what was wrong with it, none of those in the disease handbook described the same thing either. I ended up pruning the effected pads because it kept spreading. It seems to be doing better now but I havent looked at the roots yet.

It definitely wasnt mealybugs. There were never any dead bugs with alcohol or with taking a papertowel and tryng to squish anything that would be there. Even took tweezers and bugs never come off the cactus, only the white layer. Im not sure what it was but I did a couple hours worth of research on bugs, fungi, and diseases that affect the prickly pear cactus, and on ones that affect many cacti in general, and that turned up nothing.

Thank you for all of your help though, it is very appreciated!