Hi there, a couple of my cactus seedlings have developed small red/orange spots. I'm guessing this is probably rot, and I've lowered the humidity in the propagator which seems to have stopped them growing any bigger or developing anymore at least.

They're not spider mites or anything like that, they're actually on the cactus itself and they seem to be congregate around spikey areas mostly, presumably because these areas are smaller, weaker and more prone to it.

Is my diagnosis correct? Is it just rot caused by too much humidity and hence water dripping down from the roof of the propagator? I've certainly managed to stop the propragator getting steamed up now so if so I think they'll be fine - they certainly seem happier since. Will this cause long term damage to the plants?

Thanks in advance!

it may be rot, but cacti should certainly not be in a propagator once they have germinated, that's just asking for trouble....they like dry air

Cheers, that's the impression I've got watching these grow, they definitely seem happier with the propagator lid off but many guides suggest leaving them in such conditions for 6 to 12 months such as the sealed bag method and so on unless I've misunderstood them somehow they just mention having a small gap like the vents on the propagator lid for air.