aphids? some kind of spray, I don't know if dust would work or not, never used it. Neem oil or something... I'm not an expert, haven't had bad aphids on my maters in a few years. Can you get a pic of them maybe?
Dish soap and water in a spray bottle and spray down all your plants real good. Works on white flys when they're on my plants. Diatemaceous Earth might work too but not good for the bees. You can get food grade DE at TSC.