This afternoon I was pruning some annual ranunculus in one of my mulch beds and noticed a massive number of tiny (almost microscopic) bugs crawling all over them and the soil around them. Thus far this spring, the ranunculus have all been flowering beautifully but the foliage has gotten progressively worse - first turning yellow, then brown. Most of the plants have little foliage left. There are also a couple of dwarf azalea and boxwoods in the back of this particular mulch bed that don't seem to be affected (yet!).

I'm guessing that the condition of my plants is due to the presence of these insects. I tried to get a picture but they are too small. They are very tiny, the size of a pin point, and appear to be a yellow or light brown color. There are probably hundreds of thousands of them. If you touch the area near them, they jump in a way that reminds me of fleas.

My initial thinking is that they are spider mites, but I don't see any of the webbing that seems to be a key element to diagnosing them. Granted, I ran the irrigation system this morning, which may have damaged the webbing. Does this sound like spider mites? If not, what else could it be.

Thanks in advance for your help!