Found these on the leaves of avocado, pomegranate, blueberry and several other plants. Are those spider mites or some other pest?
Looks like mildew. Spider mites eat the chloraphyl turning leaves to a bronze color. Easily seen under a pocket microscope like the one sold by Radioshack for around $15.
The white threads tip off this as a whitefly infestation. Sometimes mold occurs from the honeydew left behind by the whiteflies. Good luck!
Here is a link that might be useful: Whiteflies