4

I've been away for the last two and a half weeks, and upon return I noticed a few of my cacti had developed white fuzzy spots, which were not there before.

In the worst instance, one cactus appears damaged and oozes brown liquid in one spot, as well as something that looks like sweat on the rest of its body.

I watered all of the plants profusely 10 days before leaving (which was roughly 1 month ago), and was sure to remove excess water from the pots. Before this watering, the last time I watered the succulents was 2 months prior.

Almost all of the affected plants are placed in a miniature greenhouse from IKEA. Due to an oversight, I left both top panels closed before leaving, so I assume air circulation was limited.

The plants are in front of a south-facing window, and on sunny days it they can get large amounts of light and warmth, so the lack of air circulation may have affected them negatively.


I read an article saying that the white spots may be caused by mealybugs. It seems treatable but I'd like to understand whether this is actually the cause of my issue and what the best way to treat this instance would be.

My questions are:

  • What are these white and brown spots on the succulents?
  • Is there something that can be done to eliminate them and heal the plants?
  • What is the cause of this issue, how did it spread to so many plants at the same time, and how can I prevent it reoccurring?

EDIT: It seems like this is a very widespread mealybug infestation. I spent today removing as many as possible, but I'm sure there's more. They're on at least 10 of the plants, maybe more. I'm not sure how they've spread so fast and so widely (I hadn't seen any prior to leaving my house 3 weeks ago, though admittedly maybe I hadn't looked carefully enough). Do you have any tips for clearing these entirely?


This is the cactus with white spots and a large brown spot of fluid oozing from one point on its body:


This one has multiple fuzzy spots and some less fuzzy and more defined small white spots:


This one has just one fuzzy spot on one of the tips:


This one has spots all over its body:


In one instance there are spots on the soil:


Two of the cacti outside the greenhouse also have fuzzy white spots. The white spots are new on the one in the first picture, but the one in the second picture has had fuzz at the top for a long time and I'm not sure if it's due to the same causes.

  • 1
    Are you using tap water, tap water with vinegar, or distilled water? – Graham Chiu Feb 22 '18 at 20:27
  • For these plants I’ve only ever used two water. – Gabriele Cirulli Feb 22 '18 at 23:00
  • Is that a brand? – Graham Chiu Feb 23 '18 at 0:31
  • Sorry, not sure how the two ended up in there! I’ve only ever used tap water. – Gabriele Cirulli Feb 23 '18 at 5:29
  • 1
    It seems like this is a very widespread mealybug infestation. I spent today removing as many as possible, but I'm sure there's more. They're on at least 10 of the plants, maybe more. I'm not sure how they've spread so fast and so widely (I hadn't seen any prior to leaving my house 3 weeks ago, though admittedly maybe I hadn't looked carefully enough). Do you have any tips for clearing these entirely? – Gabriele Cirulli Feb 25 '18 at 16:50
0

Is the white stuff soft or hard or brittle hard and does it resemble this

latex oozing

in which case it would be a Mammillaria oozing sap from damage.

http://www.sbs.utexas.edu/mauseth/ResearchOnCacti/Poisons.htm

  • In your picture, are you referring to the fuzz between the tips or the white solid-looking clumps at the tips? – Gabriele Cirulli Feb 23 '18 at 20:11
  • Pretty sure he was talking about the white blobs on the tips, not the felt in the valleys. Some Mammillaria have milky "sap", and others are less so. This is generally true for cactus and succulents. When the plant is injured it will ooze sap. – Tim Nevins Apr 26 '18 at 19:58
  • @GabrieleCirulli that gives it its name, the milky sap on the tips. – Graham Chiu Apr 26 '18 at 20:27
  • Thanks, in my case I think it's in fact a mealybug infestation. I've got a few visible large mealybugs (about 1 mm long) that look the same as what you see when you search for mealybug on Google Images. The fuzzy spots seem to contain powdery eggs that fly around when disturbed. Quite disgusting. I've been trying to remove them from the plants as I see them, and spraying them with isopropyl alcohol in the worst instances, but they're quite persistent. – Gabriele Cirulli May 3 '18 at 8:44
  • I agree, it's mealy bugs. Separate infected plants from non-infected and start treatment. You need to be prepared to repot the infected plants completely replacing the soil if you have root mealies too. Do you have a mealy treatment plan? Start by physically removing all visible bugs (kill them!). Use tweezers. Good luck! – Tim Nevins Aug 24 '18 at 21:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.