Poorly plant

Sunnyspot

Hi there 
I have a very large , long life Christmas cacti, it flowers brilliantly , especially in the summer. Right now its looking not too good. I've noticed areas that are looking 'woody' and leaves have dust/plant pests  or something ??  It sits by sunny window with spells in shadier area if too hot. In one picture i have a mug by the side of it so you can see just how big this is 
Any ideas ??  Spray with washing up liquid etc?  Not currently looking to split and divide 

BobTheGardener

It is looking a bit sad and also looks a bit dry to me.  I can't identify the pest from the photos but the white 'fluff' in the last photo look like aphid carcases.  One way of treating it would be to submerge the whole thing, pot leaves and all, in water for 20 minutes.  The compost will then get throughly wetted and any pests will drown.  The only problem is that is such a large plant that you may have difficulty in finding anything big enough to do that, unless you have a plastic dustbin or use a bath.  If that's not an option I would try a systemic bug spray (because it's an indoor plant, so the insecticide poses little or no danger to pollinating insects.)  Soapy water spray may be worth a try but you'll need to spray both side of each and every leaf to eradicate them, and probably more than once.

The last photo also shows it is producing aerial roots, another indication that it could be too dry.

Sunnyspot

Thank you so much Bob , plenty of ideas there to get me going!
Many Thanks !