7 dust will kill them but it's hard to get to where they live. They like under the leaves and stems. They won't bother the tomato plants to my knowledge.
Once established they are hard to get rid of. Make sure to plant your squash in a different area next year. For a great preventative I make an organic mix of hot sauce, garlic, dab of dawn q.s. To a gallon of water and put on a hand held yard sprayer. Can spray everything in the garden with it, including corn silks.