origination of spider mites

i live in zone 5 and have lime trees and a bananna in my house . spider mites showed up one day with a vengance. i do spray and sometimes cut back some of the plant. Do the mites maby come out of the powder fertilizer? Just where do they come from? The plants appeared clean when i got them and were good foor almost 2 years. What happened? Thanks Sue

Doug is tempted to say that they "just appear" :-) but the reality is that they're an insect. They might have been carried in on the coat of a pet. On gardener's clothes. On another houseplant. There's a ton of ways other than magic they might have appeared or been transported into the house. :-) But nope, they're not in the fertilizer.

On the other hand, maybe they're "magical mites" rather than spider mites. :-)

But assuming they're the regular kind, you get to be unbelievable vigilant and employ a constantly revolving method of control for them on these plants. Banana trees are like magnets for this pest - I had a large "pet" banana tree in the greenhouse and wound up trying to see if it was winter-hardy in February because we just couldn't control the mites and they were infecting the rest of the greenhouse. By the way - the banana didn't survive. ;-) Good luck