What are These Tiny Little Tick-Like Bugs on my Rudbeckia?
The insects you see on your rudbeckia are aphids and they are easily controlled. The easiest control is to spray them off with a hard spray of water. They can also be controlled by spraying the plants with insecticidal soap or horticultural oil, but do not use these products when temperatures are in the 80's. Spray on cool, cloudy days. These insects can also be controlled by standard insecticides, but these products also kill beneficial, predator insects. You could also use a systemic soil drench insecticide.
It is important to examine the plants for the presence of lady bird beetles and their larvae before spraying. These insects will usually control the aphid population to a tolerable level.