they will most likely be white flies little critters love the underside of leaves so flip one over and have alook what your dealing with in my expoerience the best way of dealing with any tiny little pest like this is mother nature reasearch and buy some lady birds and set them loose near your plant they can eat upto 50 aphids mites white flies a day and live upto 2 years with a good food supply they will eat them all away. other than that i have heard of things like steel wool around the base of the plant to stop them jumping up from the soil to get at your plant litratrally shreds them google it my friend you have options :)