Cactus blemishes

[purzo]

I have these blemishes on some Rebutias and a Tephrocactus. They're raised, hard and don't scratch off easily. Could anybody suggest a cause and whether they might be contagious. Any suggestions for treatment would be appreciated but they look permanent to me. They don't appear to be scale and I don't think they're sun scorch,so possibly mite damage but I really don't know.

Thanks for any suggestions.

[Stuart]

Looks like scale to me, particularly on the Rebutia. Isolate and treat with SB Plant Invigorator weekly for a few weeks.

Stuart

[Ali Baba]

Not scale, you don’t get marks with scale, just scales! Looks like thrips damage to me, typically occurs in the winter on Rebutia around the growing point and the damage appears and expands as the plant grows, by which time the thrips have grown up and flown away

[Flayzerflay]

If the raised bumps have a darker dot in the middle it's scale, you may just have several generations expanding their empire.

Systemic is required so they get poisoned.

[purzo]

Thank you for the replies. I had discounted scale because I've had examples of them before, so I knew what they look like, but I'll definitely have another look and try SB Invigorator anyway as I have some somewhere. Ali's thrips theory sounds interesting although I have rarely seen any in my greenhouse. If it was them then they seem to have moved on as I couldn't spot any under a magnifying glass.

What with mealies, root mealies, RSM and now possibly thrips to be constantly on the lookout for it does take the shine off the hobby after a while.

Thank you all.

[Flayzerflay]

Makes you wonder how the Thai growers never get these issues, i suspect it's the systemics used are furan based and hence banned.

[Eric Williams]

I have read that scale has thousands of species,affecting plants. Some are flat, others raise tiny brown lumps. Take your pick lol.

[purzo]

If the raised bumps have a darker dot in the middle it's scale, you may just have several generations expanding their empire. Systemic is required so they get poisoned.

On another Rebutia the bumps did indeed look as though they might have a darker dot in the middle. So maybe there are several generations or just a tiny lumpy species as Eric suggested.

I've sprayed with SB Invigorator and will repeat for a few weeks to see how it goes.

[iann]

My first thought was oedema. Scale can be scraped off fairly easily. It may leave a mark but not cause a lot of damage. Trying to scrape off oedema or scars from any other reason will not be easy and will cause significant damage.

[purzo]

My first thought was oedema. Scale can be scraped off fairly easily. It may leave a mark but not cause a lot of damage. Trying to scrape off oedema or scars from any other reason will not be easy and will cause significant damage.

Thanks Iann

I've tried scraping again and it's not budging, I feel I'd definitely have to damage the plants to remove any. Googling didn't really give me any images quite like mine but according to the search results the cause seems to be over watering although not enough to kill the plant completely. I'll continue with the SB Invigorator anyway for a few weeks and continue to monitor. Thanks again