Damage, disease and pests.

[kesizewi]

HI,

This Cereus peruvianus had some slug damage in the autumn. There are now black and rust color marks. I'm guessing fungus? Most stems have some. Is it recoverable do you think? The second picture is an Opuntia from the cold greenhouse. Two pads had some rot which I cut off. This pad only has a little. Should I cut it off? Its now in the house. Finally a picture of moth damage for interest. The caterpillars like aeonium shoots as well as pelargoniums.
Any tips welcome. I'm avoiding using pesticide unless on indoor plants.

Please help.

I didn't find the right solution from the Internet.

References:
http://forum.bcss.org.uk/viewtopic.php?t=165508
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Thanks!