I've had aphids, and not just one or two, but a freakin crazy infestation...They never left anything that looked even close to the droplets in the OP's pics. Jus' sayin'. Plus, if he had an infestation to the point where he notices signs, he'd find the aphids. They're very prolific, and without treatment he would have an undeniable infestation on his hands as well.
