The problem is not an insect or a mite, but, as you first thought, rust disease.
From the sfgate.com
French said the citrus rust mite can reproduce rapidly, with a generation lasting only seven to 10 days.
From the sciencedaily.com
Will Envidor knock the citrus rust mite from atop its perch as the No.1 citrus pest of Rio Grande Valley citrus?
From the sciencedaily.com
The citrus rust mite has developed resistance to some of the existing miticides, often making treatments a futile proposition for many growers.
From the sciencedaily.com
From a distance, it looks like rust, but up close it appears to be a psyllid insect or a mite.
From the sfgate.com
Fuchsias can be prone to a variety of diseases and pests, including the virulent fuchsia mite, scale, thrips, whiteflies, rust and gray mold, to name a few.