White spots in barrel cactus

[j_cruz3k]

My barrel cactus developed tiny white spots a couple of months ago and these tiny spots has grown significantly larger and numerous new ones have surfaced. These tiny spots start as yellow green discoloration, then turned into white then starts to grow bigger.

My cactus has not been under the hail nor has it been bitten by caterpillars or visible insects to my knowledge.

Help please.

[Vic]

They're cold spots, most likely caused by low temps combined with humidity during the winter/dormant rest period. They won't do any harm apart from not looking so nice

[sue46]

Just looking at this and a thought popped into my head - in the wild would cacti develop these sort of things - burn spots, cold spots, be attacked by mealy bugs and scale? How do they survive these sort of attacks and problems in the wild?

[Liz M]

I guess the answer is that they don't survive in the wild.
Also, maybe they don't suffer burn spots and cold spots because they are outside and not cooked under glass, nor frozen like they would be here in winter. Plants grown outside don't seem to get mealy bug or scale so much. Maybe in their natural habitat there are not those pests about, I can't believe it, mind, but there would be other things like goats and birds nesting etc. I put anything suffering from those outside, in summer, it often sees off the mealy bug, anyway.

[Vic]

Just looking at this and a thought popped into my head - in the wild would cacti develop these sort of things - burn spots, cold spots, be attacked by mealy bugs and scale? How do they survive these sort of attacks and problems in the wild?

Cacti do occasionally get frost damage in the wild such as saguaros out in Arizona. Not seen much evidence of scorch, this happens more so in cultivation with temps getting too high inside greenhouses and combined with insufficient ventilation or plants suddenly exposed to higher UV levels that have been kept in shaded conditions. I have seen Opuntias with mealy infestations but not a great deal, pests in the wild will be exposed to creatures that prey on them.